Agrichemical and Environmental NewsDr. Doug Walsh, Agrichemical & Environmental Education...

Agrichemical& Environmental News

Issue No. 152December 1998

Page 1

In This Issue

For comments, please contactCatherine Daniels at the WSUPesticide Information Center,2710 University Drive, Richland,WA 99352-1671Phone: 509-372-7495Fax: 509-372-7460E-mail: [email protected]

The newsletter is on-line atwww2.tricity.wsu.edu/aenews,or via the Pesticide InformationCenter (PICOL) Web page athttp://picol.cahe.wsu.edu

...continued on next page

What if OPs & CarbamatesWere Banned? ....................... 1

FQPA: USDA Perspective ...... 3

WSDA Harmoniously SavesTolerances for WashingtonCrops...................................... 5

Subscription Reminder ........... 7

Digging for Dioxins: DoesAgriculture Have BuriedSecrets? ................................. 8

Cholinesterase Field-Test KitShows Good Potential .......... 13

Free? Unlikely ...................... 16

What if OPs andCarbamates Were Banned?Dr. Doug Walsh, Agrichemical & Environmental Education Specialist, WSU

On October 8, 1998, Steve Appel,President of the Washington StateFarm Bureau, sent a letter toJames Zuiches, Dean of theCollege of Agriculture and HomeEconomics at Washington StateUniversity. The letter expressedconcerns regarding potentialregulatory actions that may stemfrom implementation of the FoodQuality Protection Act of 1996(FQPA) and the potential fallout foragricultural producers in Washing-ton. Specifically, Appel asked ifdata had been compiled on theeconomic impact of banningorganophosphate and carbamateinsecticides. Additionally, he askedWSU to respond to seven detailedquestions.

u What would a ban on organo-phosphate and carbamate insecti-cides do to the price of major fooditems in Washington State andacross the country?

v What would happen to ourinternational markets if Washingtonfarmers were placed at a competi-tive disadvantage? What impactwould this have on the U.S. tradedeficit?

w What are the health risk trade-offs associated with such a ban?

Would the nutritional quality of fooditems change? Would diet changesinduced by higher prices for fruitsand vegetables be more or lesshealthy than the current situation?

x What are the risks associatedwith pesticides and pest manage-ment strategies that would beadopted in response to the ban?

y How much would aflatoxinincrease?

z Is it possible that mycotoxinscould become a problem under thisscenario?

{ What are the health risk trade-offs for infants and children?Recently the press reported on astudy indicating the average childis getting a large portion of his dailyvitamin intake from breakfast cerealinstead of from fresh fruits andvegetables. Would the ban cause aneven greater impact on the diets ofchildren?

Dean Zuiches appointed AssociateDean Jim Carlson to formulate aresponse to these questions. OnOctober 12, Jim Carlson as-sembled a group of WSU facultywith relative expertise in these

Agrichemical andEnvironmental News

Cooperating agencies: Washington State University, U.S. Department of Agriculture, and Washington counties. Cooperative Extension programs and employment are available to all without discrimination. Evidence of

noncompliance may be reported through your local Cooperative Extension office.

A monthly report on pesticides and related environmental issues

Page 2 Agrichemical & Environmental News No. 152 ¿ ¿ ¿ ¿ ¿ December 1998

broad topics, including Allan Felsot, CatherineDaniels, and me, from the Food and EnvironmentalQuality Laboratory. I was asked to respond to Ques-tion 4. Following is an excerpt of my reply as well assome additional comments.

“What are the risks associated with pesticidesand pest management strategies that would beadopted in response to the ban?”

It is obvious that substantial economic and pestcontrol risks and costs would result from a ban on keyorganophosphate and carbamate pesticides. At worst,a total ban of organophosphates and carbamatescould result in complete crop failures from damagecaused by insect and mite pests for which there areno viable chemical, cultural, or biological alternatives.

BiopesticidesBiopesticides and softer chemistry pesticides areoften listed as alternatives to organophosphates andcarbamates. They can be more costly and less effec-tive at suppressing pest insects and mites. (Ifbiopesticides could provide consistent and cost-effective pest control, why don’t they command agreater part of the pesticide market already?)

Some biopesticides and cultural techniques, includingmating disruption, contribute to the economic controlof some pests. Several new biopesticide chemistriesprovide extremely effective control of some key pests,but in a trend that follows traditional chemistries,development and registration for these products haslagged on minor crops. Other concerns associatedwith biopesticides are that they have often provenineffective at suppressing arthropod pests with pierc-ing-sucking mouthparts like spider mites, aphids, andtrue bugs, and pests with rasping sucking mouthpartslike thrips.

Biopesticides often target species or specific groupsof insects. Organophosphate and carbamate insecti-cides will typically control a broad range of pestinsects and offer some flexibility in the length ofresidual control provided since some organophos-phates and carbamates have short residual periods

while others can remain biologically active for anextended time period.

Biological ControlPests can often be controlled biologically if disease orbeneficial predators or parisitoids are sufficientlyabundant. Numerous incidences of introduction ofexotic beneficial organisms resulting in successfulsuppression of pests have been documented. Thereare several citations of successful pest control result-ing from inundative release of beneficial arthropods.However, cost of these biological methods can beprohibitive. The biological control agent may beexpensive and since the organisms are alive theymust be distributed into the field gently. Releases canentail some risk-taking since the quality and quantityof the biological control purchased can vary betweenvendors and between orders from the same vendor.Release of beneficials requires patience since there isan establishment period and typically no rapid knockdown of infesting pest populations. It can also belabor- and/or time-intensive since the pest populationmust be sampled and monitored closely so that itdoesn’t exceed the control-action threshold andrequire (typically chemical) suppression. Inundativereleases have focused primarily on high-value/high-management crops or instances where regulatory orpest resistance constraints have left producers withfew other effective alternatives.

Chemical AlternativesUse of photo-stable synthetic-pyrethroid insecticideswould increase if organophosphate and carbamateinsecticides were banned. I have been involved withresearch proving that pyrethroid insecticide residuespersist at biologically disruptive concentrations formonths and possibly even years following field appli-cation on plant materials. Pyrethroid residues accu-mulate and are additive from multiple applications.Pyrethroids are biologically disruptive and their usewill often result in a resurgence of the target pest orlead to an outbreak of secondary pests includingspider mites or thrips. Additionally, many key pestspecies have documented histories of rapidly devel-oping resistance when exposed to multiple pyrethroidapplications in a season or over several years. Agri-

…if OP’s and Carbamates Were Banned, cont.

Dr. Doug Walsh, Agrichemical & Environmental Education Specialist, WSU

Agrichemical & Environmental News No. 152 ¿ ¿ ¿ ¿ ¿ December 1998 Page 3

cultural producers could be faced with increasedcosts associated with pest control of secondary pestsand crop damage caused by secondary pests. Pesti-cides registered for control of secondary pests canhave strict regulations regarding use and re-entry. Inmany minor crops timing of cultural manipulations tothe crop is critical to production. Producers will incureconomic loss from the downtime associated withlong re-entry intervals if they are not able to work intheir fields at critical crop production junctures.

Ecological ConsiderationsA ban of organophosphate and carbamate insecti-cides could change the arthropod complex in theagroecosystems of many minor crops. There’s notelling what pest currently suppressed by organophos-phate and carbamate insecticide technologies couldemerge from a complex in which it was no longersuppressed.

Additionally, it could prove difficult to eradicate orsuppress exotic pests that might be introduced intoWashington in the future without organophosphate orcarbamate pesticides. The establishment of newexotic pests in Washington could result in significanteconomic losses if agricultural commodities arebanned from domestic or export markets. It is nearlyimpossible to estimate the effect of the introduction ofan exotic pest on the agricultural community.

Pests of FinanceAgricultural producers have relied on organophos-phate and carbamate pesticides to maintain effectivepest control; this reliance has mitigated risk to farmloan and crop insurance underwriters. The uncertaintyassociated with a ban on organophosphates andcarbamates would undoubtedly increase crop insur-ance and farm loan interest rates, thereby increasingproducer’s costs in yet another way. Additionally, acredit crunch could result as loan underwriters be-came unwilling to accept the increased risk.

Bottom LineCrop producers using marginally effective pest con-trols would not only incur costs due to crop damagebut would also be faced with increased labor costs forculling damaged product. Chemical alternatives couldcreate more problems than they solve. Future ecologi-cal considerations are a wild card with potentiallydisastrous consequences. Increased difficulty inproducing a salable crop economically could result inincreased insurance and financing costs, or even lossof insurability or credit.

Dr. Doug Walsh is the Agrichemical & EnvironmentalEducation Specialist at WSU’s Irrigated AgricultureResearch & Extension Center in Prosser. He can bereached at (509) 786-9287 or [email protected] to the other six questions posed by WSFB willbe summarized in the January issue of AENews.

FQPA: A USDA PerspectiveDr. Allen L. Jennings, director of USDA’s Office of Pest Management Policy

The Food Quality Protection Act of 1996 (FQPA)charges the Department of␣ Agriculture (USDA) withcreating a minor use program, furthering integratedpest␣ management (IPM) research and application andgathering basic data used in␣ pesticide exposureanalysis. These data are fundamental components ofthe␣ Environmental Protection Agency’s (EPA’s) riskassessments and include pesticide use surveys,pesticide residue analyses, and food consumptionsurveys.

This article was originally printed in Farm Bureau News, Vol. 77, No. 36. Reprinted here with author’s permission.

The Vice President’s April 8, 1998, memo to USDASecretary Dan Glickman and␣ EPA Administrator CarolBrowner emphasizes the role of USDA in its partner-ship with EPA in FQPA implementation. USDA iscommitted to a close,␣ long-term working relationshipwith EPA to help ensure that FQPA␣ implementation isbased on sound science, transparent processes,ongoing␣ stakeholder involvement, and, when neces-sary, orderly and predictable␣ transitions in the pestmanagement strategies of agricultural producers.



…USDA Perspective, cont.

Dr. Allen L. Jennings, director of USDA’s Office of Pest Management Policy

USDA Role in Risk AssessmentUSDA will help ensure that pesticide risk assess-ments are based on sound␣ science by continuing toprovide high quality and credible data exposureassessments. The department will seek to expand thecurrent data collection␣ programs and utilize theexpertise of the land grant university system to␣ meetthe demands of FQPA. USDA will maintain ongoingstewardship of the data␣ by clearly identifying itsstrengths, weaknesses, and limitations, and will workwith EPA to ensure appropriate and optimal use ofthe data.

Specific data collection efforts include surveys ofpesticide use and␣ integrated pest managementpractices, food consumption surveys, and pesticideresidue monitoring. The department will work withEPA to identify and␣ develop improved risk assessmenttools and will be an active partner with EPA in␣ thedevelopment of chemical risk assessments and theunderlying risk␣ assessment policies and guidelines.

USDA Role in Risk ManagementWhen risk assessments, based on the best possiblescience and data, indicate␣ excessive risk, USDA willuse the crop-pest profiles now under development␣ toidentify crop production issues, pest managementalternatives, research␣ needs, and opportunities forrisk mitigation. The department will ensure that agri-cultural producers are aware of and involved in therisk management␣ processes. In consultation withcrop production experts and agricultural␣ producers,USDA will effectively reduce risk to acceptable levelswhile␣ preserving critical pesticide uses, particularlyIntegrated Pest Management (IPM) and resistance-management programs. Through the Office of PestManagement Policy, the land␣ grant institutions havebegun the process of developing and publishing(on␣ the Internet) state-level crop profiles. Theseprofiles summarize basic␣ agronomic information oneach crop in each state and focus on major pests␣and management practices. Specific attention ispaid to IPM and resistance␣ management programsand needs.

USDA Role in Transition StrategiesIn those cases where cancellation of a critical use is theonly effective␣ regulatory mechanism to reduce risk toacceptable levels, USDA will work␣ with EPA, agriculturalproducers, and crop production experts to developand␣ implement approaches that allow growers to moveto new or revised pest␣ management systems withoutsignificant disruption of domestic production.

Because the successful introduction of alternative pestmanagement controls␣ depends, in part, on the timelyregistration of new products, USDA will work␣ closelywith EPA to develop priorities and schedules for deci-sion making.␣ Crop profiles will provide much of thebasic data needed for determining␣ priorities andidentifying vulnerable crops. As such, the crop profilesare␣ basic to both risk management and to the develop-ment of transition␣ strategies for crop-specific pestmanagement needs.

USDA has also developed a “pipeline database.” Thedatabase identifies␣ unregistered products that arelikely effective pest management chemicals␣ for spe-cific crop-pest combinations. The database consists ofresearch␣ currently under way, products that havebeen in use under an emergency␣ exemption, andproducts currently being used under experimental usepermits pending full registration applications. Productsin any one of these␣ categories have the potential forregistration within a few years and could␣ be keyelements in strategies to phase out or reduce the riskof␣ particularly high-risk pesticide uses.

Finally, both short- and long-term pest managementresearch programs are␣ being examined and retooledto respond to FQPA-driven needs. Processesfor␣ establishing research priorities and programs willmake much greater use of␣ stakeholder input.

For questions regarding crop profiles, contact yourstate’s Pesticide Impact Assessment Program (PIAP)liaison, or Dr. Catherine Daniels, WSU PesticideInformation Coordinator and Washington state PIAPliaison, [email protected] or (509) 372-7495.


When the Environmental Protection Agency (EPA)announced early this year that they were proposing torevoke 871 pesticide tolerances, our keenly intelligentinitial response was “They’re gonna do what?” fol-lowed quickly by “Cancel 871 tolerances??!! Is this atypo?” What was going on? Was EPA undertakingsome sort of tolerance deforestation effort? Visions oftolerances toppling right, left, and center ran rampant.Besides noting the sheer number of tolerances beingdiscussed, alert Federal Register reviewers like usalso noticed the mention of phosphamidon use onapples. Alarm bells very disharmoniously began tosound: Caution! Caution! Caution!

Tolerance reassessment requirements set forth in theFederal Food, Drug, and Cosmetics Act task EPA withreviewing some 3,200 tolerances by August 1999. Inefforts to meet this mandate, EPA reviewed theirbooks and identified tolerances they believed met twocriteria: first, that no current registrations existed forthese specific crop-pesticide combinations, andsecond, that existing stocks of products labeled forthese uses had been depleted. This proposed actionwas basically a “housecleaning” effort by EPA, in-tended to delete any unnecessary tolerances beingcarried in the regulations. It has been the agency’spolicy to issue a final rule revoking tolerances whenthere are no active registrations under FIFRA (FederalInsecticide, Fungicide, & Rodenticide Act). EPA’sconcern has been that retaining “unnecessary” toler-ances might encourage the misuse of pesticides.With this in mind, perhaps our concern was un-founded. Or was it…

Our initial action (and, yes, probably the easy part)here at WSU’s Pesticide Information Center (PIC) wasa search of the Pesticide Information Center On-Line(PICOL) label database based on each proposedrevocation. We entered each crop-pesticide combina-tion into the database to see if PICOL showed anyactive registrations. Next, as all good PICOL usersmust, we pulled the labels and had a look-see toverify that, where the database said they existed,registrations really were still in place. We found manycases where registrations still existed in Washington

WSDA Harmoniously SavesTolerances for Washington Crops

for crop-pesticide combinations EPA was proposingto axe.

At this point it became clear to the PIC staff that it wastime to bring in reinforcements and, in a transparentlyharmonious manner, the Washington State Departmentof Agriculture entered the fray. WSDA’s PesticideManagement Division agreed to act as the interfacewith EPA. They kindly stepped up and took the lead incollecting more registration data, contacting growersand commodity/commission groups, and then submit-ting comments on behalf of Washington agriculture toEPA. When the dust settled, most of the tolerances onwhich WSDA commented were left standing.

Here’s a quick look at what WSDA accomplished:

Phosphamidon: AppleEPA proposed revoking the tolerance for use ofphosphamidon on apples, believing that existingstocks had been used. WSDA was able to point outthat while no active phosphamidon registration ex-isted, Washington apple growers had retained asizeable phosphamidon inventory—a six-to-eight-yearsupply, according to industry representatives’ esti-mates. In their October 26, 1998, Federal Registernotice, EPA agreed not to revoke the tolerance forphosphamidon on apples in this action. But EPAdoes intend to revoke this tolerance so… if youhave phosphamidon on hand, use it up. (Note thatNorthwest Wholesale, Inc. also submitted commentson this proposed revocation, stating that they believedexisting stocks might last up to 10 years.)

Cryolite: Collard, Blackberry, Boysenberry,Dewberry, Loganberry, YoungberryWSDA commented that active registrations existed forthe use of cryolite on these crops. The collard use isvia a Section 3 label and the other uses were, at thetime, authorized via SLN WA-980001 (Special LocalNeeds, derived from Section 24c of FIFRA). πEPAacknowledged that including collards in the proposedrevocations was an error. (It is noteworthy that out of


Jane M. Thomas, Pesticide Notification Network Coordinator, WSU


all the registrants who must have reviewed this notice,WSDA was the only commentor regarding the cryo-lite-collard tolerance.) Following the February 5 initialnotice, EPA notified WSDA that blackberries, boysen-berries, dewberries, loganberries, and youngberriesmust be removed from the 24c label; on May 13,1998, WSDA issued a revision to SLN WA-980001limiting its use to blueberries, raspberries, and straw-berries. As an aside, WSDA indicated that Gowanwould request these crops be reinstated on the 24cafter IR-4 submits completed data packages. (In aneffort toward greater transparency, why not retain thetolerance so that it will be in place when the 24c isrevised again?)

Copper Oleate: All CropsEPA proposed revoking the exemption from therequirement for a tolerance for copper oleate on allcrops. WSDA, along with Griffin Corp., requested thatthe exemption be retained and EPA’s 10/26/98 deci-sion was not to revoke the exemption at this time.

ODDA: Apricot, Cherry, Nectarine,Peach, Plum, PruneWSDA verified that active registrations exist for theseuses and requested that EPA retain these tolerances.EPA’s response was as follows:

Since ODDA is a lepidopteran pheromone, it willremain covered under the broader tolerance exemp-tion of 40 CFR 180.1153 Lepidopteran pheromones;exemption from the requirement of a tolerance.Therefore, the current tolerance exemptions listed forODDA under 40 CFR 180.105 are not needed and willbe revoked by the Agency.

Ferbam: BoysenberryWSDA pointed out that a 24c registration existed(WA-940029) for the use of ferbam on boysenberries.EPA’s decision was not to revoke the tolerance onboysenberries. As a comment, this seems onlyappropriate (not to mention transparent and harmoni-ous), since one of the criteria for retaining tolerancesis that they have a FIFRA-registered use and SLNsclearly meet this condition.

Trichlorfon: CattleWSDA found that trichlorfon was registered for useas a pour-on insecticide for cattle. They, along withBayer, requested EPA retain the tolerances for thiscompound in cattle fat, meat, and meat by-products.EPA has agreed not to revoke these tolerances.

Propachlor: CornBoth Monsanto and WSDA commented that activeregistrations still existed for propachlor on corn. EPAagreed that the proposed revocation for tolerances forpropachlor on corn forage and grain was in error andagreed to retain these tolerances.

Naled: Cucumber, Forage LegumeWSDA was joined by the Canadian HorticulturalCouncil, Amvac, and Valent in commenting onproposed revocations for a host of naled tolerances.WSDA’s comments were limited to cucumber andlegume uses where active registrations still exist inWashington. The final decision was in favor ofretaining both the cucumber and forage legumetolerances.

Atrazine: GrassWSDA identified active registrations for use of atra-zine on grass. EPA acknowledged that Drexel hasregistrations for use of atrazine on orchardgrass,pastures, and rangeland. EPA’s final decision was toretain the atrazine tolerances on range grass,orchardgrass, and orchardgrass hay.

Dichlobenil: Stone FruitUniroyal commented that it had a product labeled foruse on cherries and, while it was supporting bothsweet and tart cherry tolerances, it would not supportuse on other stone fruit. (In its comment letter to EPA,WSDA also requested that the dichlobenil-stone fruittolerance be retained; however, in the final FederalRegister notice, EPA did not mention WSDA’s com-ments.) EPA determined that it would not revoke thestone fruit tolerance for dichlobenil until it had re-viewed existing data on cherries and established anappropriate tolerance level. At that time, EPA intendsto proceed with revocation of the stone fruit tolerance.



WSDA Saves Tolerances…, cont.


With more tolerance reviews ahead between now andAugust 1999, a review of the “lessons learned” fromthis process is in order. In many cases, EPA wasproposing to revoke tolerances where active registra-tions, either Section 3s or 24cs, existed. In othercases, EPA was proposing to revoke toleranceswhere the use had only recently been deleted fromthe product label and substantial product was still intrade channels. Therefore, the first lesson learned isreview proposed revocations with respect to yourown crop-pesticide combinations—it’s time well spent.

Lesson number two is take the time to submitcomments to EPA. The tolerance you save may beyour own. Of the twenty-two ingredients for whichEPA proposed tolerance or exemption revocations,WSDA submitted comments that were included indecisions made on ten of the ingredients. Of the tenissues on which WSDA submitted comments, eightwere decided favorably, one was found to be a non-problem, and one (cryolite on berries) was decidednegatively. Based on the Federal Register noticeannouncing EPA’s final decision, it is interesting tonote that WSDA submitted a greater number ofcomments than any other party involved in this action.The other commentors were twelve registrants, two


international concerns, and seven research/commod-ity groups. No other state’s department of agricul-ture submitted comments on this action.

Our point? Hats off to WSDA for a great effort!

Jane M. Thomas is the Pesticide NotificationNetwork (PNN) Coordinator for the PesticideInformation Center (PIC) at WSU. She can beharmoniously contacted at (509) 372-7493 ortransparently and electronically accessed [email protected].

A suggestion was recently made thatanyone associated with Food Quality

Protection Act issues be fined $5 each timethey use a derivative of buzzwords du jour

“transparent” or “harmony” in any written ororal communication. In an effort to live inharmony with this concept the author hasdonated $45 to the Pesticide Professionals

Entertainment Fund (PPEF). What…you havea better idea? Talk to Dear Aggie:

[email protected].

WSDA Saves Tolerances…, cont.

1999 SUBSCRIPTION—ACT NOW!It’s time to renew your subscription for the Agrichemical and Environmental News. The $15 annualfee, which covers the costs of printing and mailing the newsletter, gets you 12 issues of fascinatinginformation and riveting reading in 1999. Please make the check out to WSU, and mail it to:

Pesticide Information CenterWSU Tri-Cities

2710 University DriveRichland WA, 99352-1671

Web access to the newsletter remains free; the URL is http://www2.tricity.wsu.edu/aenews or viathe main Pesticide Information Center page at http://picol.cahe.wsu.edu. But to send your hard-copy subscription without interruption, we must have your check by December 15, 1998. Directany questions or comments to Sally O’Neal Coates at (509) 372-7378 or [email protected].


Dr. Allan S. Felsot, Environmental Toxicologist, WSU

Here we go again. Agriculture, having survived theheavy metal mania of last year, is now bracing for thedioxin dilemma. During the process of testing fertiliz-ers for heavy metal content, the Washington Depart-ment of Ecology discovered that some fertilizers andamendments contain dioxins. Now WDOE hasproposed a study that would sample agricultural soilsfrom around the state for analysis of dioxin levels.Meanwhile, WDOE released a report in July, theWashington State Dioxin Source Assessment (Yake etal. 1998), that details sources of dioxin generationand estimates loads emitted to the environment.Pertinently, some of these dioxin generators aresources for agricultural amendments. For example,hog-fuel (wood-waste) boilers create an ash that canbe used as a liming amendment.

Given the ubiquitous nature of dioxin sources in thestate, and the fact that amendments contain dioxins, ahypothesis that agricultural soils are contaminatedwith dioxins seems plausible.But can it be proven that fertiliza-tion practices have significantlyaltered levels of dioxins in soil?More importantly, if dioxins arefound in soil, do they pose ahazard by significant transferto food?

“Dioxins” Is a CatchallTerm for Many DifferentCompoundsThe term dioxins actually repre-sents 210 different compounds.The basic structure of dioxins,shown in the figures, consists oftwo six-membered carbon rings(i.e., benzene rings) joinedtogether by either one or twooxygen atoms. The compoundswith two oxygen atoms bridging the benzene rings arecalled dibenzodioxins (or dioxins), and those with oneoxygen atom are called dibenzofurans (furans).Because both types of basic structures have one ormore chlorines attached at different positions on the

Digging for DioxinsDoes Agriculture Have Buried Secrets?

benzene rings, they are properly called polychlori-nated dibenzodioxins (PCDDs) and polychlorinateddibenzofurans (PDCFs). The compounds of concernare those with four or more chlorines. In this essay,the term dioxin will be used as a convenient designa-tion for both PCDDs and PDCFs.

Each of the carbon atoms of the benzene rings isassigned a number as shown in the figures. Thus,2,3,7,8-tetrachlorodibenzodioxin (commonly abbrevi-ated as TCDD) has four chlorine atoms attached tothe carbons of the benzene rings at the positionsindicated by the numbers. Given the number ofavailable carbon atom positions accommodating fouror more chlorine atoms, 75 and 135 forms of PCDDsand TCDFs, respectively, are possible. Each form iscalled a congener.

The Deadliest Dioxin of Them AllAmong the dioxin congeners, TCDD is considered the

most toxic. TCDD was firstdiscovered over thirty years agoas an impurity in pesticide formu-lations containing the herbicide2,4,5-T, the wood preservativepentachlorphenol, and antibacte-rial soaps with the active ingredi-ent hexachlorophene. Alarmswept through the toxicologicalcommunity because TCDD hadan LD

50 (lethal dose to 50% of the

test animals) to guinea pigs ofone microgram per kilogram ofbody weight (1 µg/kg) and to ratsof 22 µg/kg! (Consider thataldicarb (Temik) is one of themost toxic insecticides, and itsLD

50 is 1000 µg/kg in rats.) Given

the presence of TCDD in com-monly used products, toxicolo-

gists were relieved to find that humans seem to bethousands of times less susceptible to TCDD thanrodents. Indeed, the only known acute effect ofTCDD exposure in humans is a severe acne-like skindisease called chloracne.

O

O

Cl

ClCl

Cl

12

3467

89

Cl

Cl O

Cl

Cl

12

3467

89

Structure of 2,3,7,8-tetrachlorodibenzodioxin.The carbon atoms are not shown, but are

represented by the points of each hexagonalbenzene ring. There are 75 possible forms

having one or more chlorines.

Structure of 2,3,7,8-tetrachlorodibenzofuran.

There are 135 possible forms havingone or more chlorines.



Dioxins and Chronic Disease:Feared but Not ProvenEPA and WHO (the United Nations World HealthOrganization) now consider dioxin a human carcino-gen, largely based on the weight of the evidence fromrodent feeding studies and epidemiological studies.One cancer in particular, soft-tissue sarcoma, hasbeen linked with exposure to TCDD, but it is a veryrare disease. While the carcinogenicity of TCDD andother dioxins is still arguable in the toxicologicalcommunity, the debate has moved beyond cancer toendocrine-disrupting effects. Indeed, high doses ofTCDD given at appropriate times during a rat’s preg-nancy can cause birth defects and reproductiveabnormalities in the offspring. Throw in possibleeffects on male testosterone levels, decreased spermcounts in rats, and altered immune systems, andTCDD would be classified as an endocrine disrupter.

EPA in 1994 released a draft reassessment of dioxinrisks. EPA’s Scientific Advisory Board reviews suchdrafts. Owing to conflicts over some of the findings inthe report, the EPA has yet to release its final draft.Editorial essays in scientific journals highlight theconflicts over the conclusion drawn in the draft docu-ment (Clapp et al. 1995; Environ Dioxin Risk Charac-terization Expert Panel 1995). Environmental epide-miology applied to chemical exposures is alwaysopen to negative criticism, but why so much delayabout chemicals that are not intentionally manufac-tured and serve no useful purpose?

Dioxin is Naturally UbiquitousEPA’s final conclusions about dioxin risk will deter-mine the course of regulation over dioxin emissions.But it is easier to make regulations than to carry themout, because PCDDs and PCDFs are naturally occur-ring compounds that apparently have been in theenvironment since the first fire on earth. In the late1970s, it was discovered that dioxin is produced incombustion processes such as waste incineration.While some blame PVC plastics and packagingmaterials for production of dioxin during incineration,we now know that dioxin is produced whenever woodor other naturally occurring fuels including coal are

burned. Indeed, WDOE found that hog fuel boilers arean important source of dioxin emissions in Washing-ton. Furthermore, volcanoes and forest fires report-edly release dioxin (Gribble 1994, Takizawa, et al.1994).

Scientists have drilled cores out of lake bottoms. Theage of the sediments is easily determined. Analysisof these sediments for dioxin has definitively proventhat all the congeners of concern were present in theenvironment during the earliest years of industrializa-tion (Juttner, et al. 1997). Nevertheless, dioxin levelsstarted to increase around 1935 and trended sharplyupward after World War II (Brzuzy and Hites 1996).Thus, humans may have always been exposed todioxin, but are we being exposed to too much dioxinnow? The answer to this question necessitates aninventory of dioxin sources and sinks, and a calcula-tion of expected concentrations relative to estimatedtolerable daily intakes.

Expressing the Amount of Dioxin(Minding Your TEFs and TEQs)The analytical chemistry of dioxin is one of the mostdemanding types of environmental analyses. Notonly are the concentrations incredibly small, ex-pressed in parts per trillion (ppt), but 136 possiblecongeners of PCDDs and PCDFs have four or morechlorines. Biochemical toxicology studies haveshown, however, that only compounds with chlorine inthe 2,3,7,8 positions are toxicologically relevant.Therefore, only 17 congeners are routinely analyzed.But analysis of this many compounds at one timerequires exhaustive steps be taken to avoid confusingsuch small amounts of these compounds with othernaturally occurring compounds.

Another problem is how to express the amount of all17 compounds in a single sample. If each of the 17compounds were of equal toxicity and caused illeffects by a common mechanism of toxic action, thenthey could simply be added together. But the mosttoxic congener is 2,3,7,8-TCDD followed by 1,2,3,7,8-pentachlorodibenzodioxin (PeCDD), which is nearly


Digging for Dioxins, cont.Dr. Allan S. Felsot, Environmental Toxicologist, WSU


as toxic in guinea pigs, mice, and chicks. The othercongeners are ten to hundreds of times less toxic.

In finding that dioxin interacted with a specific cellprotein called the Ah receptor to initiate a cascade ofbiochemical reactions, a method for dealing with theaggregate total of the 17 toxic dioxin congers wasborn. Studies showed that each of the congeners hadits own characteristic affinity for binding to the Ahreceptor, with TCDD having the highest affinity (Safe1990). Furthermore, none of the toxic congenerswere metabolized nor eliminated from the bodyexcept over very long time periods. Indeed, a lot ofthe body burden of dioxin is stored in fat (adiposetissue), and tiny amounts slowly diffuse into the blood.Thus, because each of the congeners is very stable inthe body, the toxic hazard of any one of the conge-ners could be expressed relative to TCDD as a toxicequivalency factor (TEF). Thus, TCDD has a TEF of1, PeCDD has a TEF of 0.5, and the least toxiccongener, octachlorodibenzodioxin (OCDD, 8chlorines), has a TEF of 0.001.

To express the aggregate concentration of the toxiccongeners, soil, water, or tissues are analyzed foreach of the 17 toxic congeners. The results areusually expressed as picograms per gram of material(pg/g), which is identical to a nanogram per kilogram(ng/kg) or a ppt. The concentration of each congeneris multiplied by its characteristic TEF resulting in anumber called the TEQ (toxic equivalence). All theTEQs are then added together to yield the sum TEQ.Thus, when any report expresses the concentrationsof the toxic PCDD and PCDF congeners, it is reallyexpressing the TEQ (as pg/g or ng/kg) relative toTCDD.

Extensive sampling and analysis for dioxins haveshown that the absolute concentrations of the com-paratively higher chlorinated congeners can bethousands of times greater than TCDD. However,changing the concentration to a TEQ also changesthe perspective to one of lesser hazard. For example,in a nationwide study of dioxin in municipal sewagesludges, EPA reported that the median concentrationof OCDD was 3500 ng/kg, which translates to a TEQ

of 3.5, nearly the same as the TCDD median concen-tration of 4.4 ng/kg (Jones and Sewart 1997).

TEQ’s Fatal Flaw?One flaw in the TEQ system persists. The TEQconcept was developed to consider a mixture of the2,3,7,8-substituted PCDDs and PCDFs already in abiological matrix. While the congeners could bedescribed as having similar physicochemical proper-ties (e.g., very low water solubility, low vapor pres-sure, and a very high tendency to sorb to soil), theirtransfer rate from soil or plants to organisms can differsignificantly (Jones and Sewart 1997). These discrep-ancies could result in overestimation of the realhazard of the more heavily chlorinated congeners.Despite this glaring problem, the universally acceptedpractice is to express concentrations of dioxin asTEQs.

The Sources and Sinks for DioxinDioxin is emitted from two sources, combustion andchemical manufacturing. The consensus of environ-mental chemists today is that combustion sourcesemit nearly all the dioxins. Incidental chemical manu-facturing processes, for example synthesis of chlori-nated chemicals or paper bleaching, account for verylittle of the estimated global mass balance of dioxins(Brzuzy and Hites 1996). Municipal waste incinera-tion accounts for over 30% of the global mass bal-ance. Pertinently, the data shown in Table 1 reliedupon a soil collection technique, indicating that soilmay be the most important sink for dioxin deposition.

Source kilograms /yearMunicipal waste incineration 1 13 0

Biomass combustion 35 0Iron metals product ion 35 0Cement kilns (burning hazardous waste) 68 0Cement kilns (no hazardous waste) 32 0Secondary copper smelt ing 7 8Medical waste incinerat ion 8 4Unleaded fuel combustion 1Leaded fuel combustion 1 1TOTAL 3 00 4

Table 1. Estimated average annual worldwide emission sources ofPCDDs and PCDFs (Brzuzy and Hites 1996)





Another little studied source of dioxin is municipalsewage sludges (Jones and Sewart 1997). Dioxinmay get into sludges from wastewater containingcombustion-derived dioxin, from road run-off, fromchemical manufacturing, or from impurities in paperproducts, detergents, and dyestuffs. Dioxin has beenhypothesized to form during chlorination of tap wateror during wastewater treatment. Because of dioxin’spropensity for sorption to solids, municipal wastewatertreatment would essentially filter out the compoundsinto the sludge.

Human Exposure to Dioxin andRelationship to Body BurdenHumans are exposed to dioxin almost solely throughthe food chain. The lead hypothesis for explainingexposure is that it occurs through the atmosphericdeposition of combustion products on foliage eaten bylivestock. Because dioxin is very stable and resistantto biodegradation, it will be stored in meat and milkand passed to consumers. Nearly 70% of totaldietary dioxin exposure has been estimated to comefrom meat and milk products in European diets (Jonesand Sewart 1997). Fish will also bioaccumulatedioxin, becoming a major source of exposure forcultural groups relying heavily on its consumption.

Direct consumption of vegetables and fruit containingdioxin residues from atmospheric deposition or fromsoil particle contamination (which largely affects rootcrops), probably accounts for no more than 10% ofthe estimated dietary intake (Jones and Sewart 1997).

The background concentration of TCDD in humans isconsidered 7–9 ppt (pg/g fat) (Fries and Paustenbach1990, Anonymous 1995). According to one exposureanalysis, to maintain the TCDD background concen-tration (i.e., a steady state concentration), a humanwould have to be exposed to 0.41 pg TCDD per kgbody weight per day (pg/kg/d). Vegetables onlycontributed about 1% to the amount of TCDD to whicha person is exposed each day to maintain the currentbackground body burden. Furthermore, beef and milkcontributed no more than 20% of the daily intakeneeded to maintain the background burden. Thus,although food is nearly the sole source of dioxin

exposure, it contributes little to the background bodyburden (Fries and Paustenbach 1990).

Are Soil Amendments ImportantSources of Dioxin in Soils and Crops?Little monitoring of fertilizers and soil amendmentshas been reported so any definitive answers awaitfurther study. WDOE analyzed several soil amend-ments and reported finding various levels of dioxinTEQ (as ppt) ranging from < 1 ppt in cement kiln dustto 340 ppt in granular zinc fertilizer made from steelmill flue dust (Washington Department of Ecology1998). When scaled up to the expected rates ofamendments application, the soil concentrationswould not have changed relative to expected back-ground levels. In England, these background levelshave been reported to range from 2–23 ppt, withurban soils being on the high end of the range (Jonesand Sewart 1997).

Sewage sludge has been legally applied as a fertilizerto U.S. and European soils for many years. A surveyof different municipal sewage sludges in the U.S.indicates that the average TEQ is 83 ppt with a rangeof 0.5–2321 ppt. In England, the average sewagesludge had 72 ppt TEQ, but the range was only 19–206. Researchers estimated that atmospheric depo-sition of dioxin exceeded inputs from sewage sludgeby a factor of 10. Thus, even when amending soilwith a seemingly high source of dioxin, the overallcontribution to the soil load is practically nil.

Several studies show that even where dioxin isdeposited in soil, uptake by crops is negligible. Onereason is that dioxins are bound strongly to soil andshow almost no capability for transfer from the soil tothe root and from the root into the stem. Lettuce,peas, and hay did not absorb dioxin from soil even atcontamination rates up to 6000 ppt TEQ (Hulster1993, Muller et al. 1994). Only root crops such aspotato and carrot had evidence of dioxin absorption,but it was limited to the peel and easily removed. Ashypothesized, airborne deposition was the source ofcrop contamination.



One interesting exception to the potential for rootuptake of dioxins occurs with two plants in the Cucur-bitaceae family, zucchini and pumpkin. These plantsseem to exude chemicals that might make the dioxinmore bioavailable for root uptake (Hulster et al. 1994).Even so, the cucumbers studied were contaminatedby airborne deposition rather than from soil uptake.

ConclusionsDioxins, a term commonly used to represent at least17 toxic compounds, are ubiquitous in the environ-ment. They are naturally produced in all combustionprocesses whether chlorine-containing plastic materi-als are present or not. Dioxins are found in lakesediments hundreds of years old, but concentrationsrapidly increased after World War II. Combustionsources are by far the major source of environmentaldistribution of dioxins, atmospheric deposition is by farthe most common exposure route, and humans areexposed via food.

Some good news looms on the horizon. A recenttrend analysis indicates that atmospheric emissionsmay be dropping, with consequent decreases ofdioxin in food (Alcock and Jones 1996). Chemicalsthat had contained dioxin as a result of incidentalcontamination during manufacturing are increasinglybanned, further reducing the importance of thispathway of exposure.

Over a billion dollars has been spent worldwidestudying dioxin. We already know a lot about itsenvironmental chemistry, and estimates of our dailyexposure are being determined with more confidencethan a decade ago. A preponderance of studies showthat crops are contaminated largely because ofcombustion processes, not because of soil residuescreated by fertilizer or soil amendments. WDOE maymake a good case on academic grounds that it wouldbe interesting to know how much dioxin is in our soils.However, it seems unlikely they will unearth any dirtylittle secrets.

Dr. Allan Felsot is an Environmental Toxicologist atWSU. He can be reached at (509) 372-7365 [email protected].

REFERENCES

Alcock, R. E., K. C. Jones. 1996. Dioxins in the environment: a review oftrend data. Environ. Sci. Technol. 30:3133-3143.

Anonymous. 1995. EPA’s dioxin reassessment. Highlights from EPA’sthree-year effort to document sources, exposures, and impact onhealth. Environ. Sci. Technol. 29:26A-28A.

Brzuzy, L. P., and R. A. Hites. 1996. Global mass balance for polychlori-nated dibenzo-p-dioxins and dibenzofurans. Environ. Sci. Technol.30:1797-1804.

Clapp, R., deFur P., Silbergeld, E., Washburn, P. 1995. EPA on the righttrack. Environ. Sci. Technol. 29:29A-30A.

Environ Dioxin Risk Characterization Expert Panel. 1995. EPA assess-ment not justified. Environ. Sci. Technol. 29:31A-32A.

Fries, G. F. 1990. Evaluation of potential transmission of 2,3,7,8-tetrachlorodibenzo-p-dioxin-contaminated incinerator emissions tohumans via foods. J. Toxicol. Enviorn. Health 29:1-43.

Gribble, G. W. 1994. The natural production of chlorinated compounds.Environ. Sci. Technol. 28:310A-319A.

Hulster, A., J. F. Muller, and H. Marschner. Soil-plant transfer of polychlori-nated dibenzo-p-dioxins and dibenzofurans to vegetables of thecucumber family (Cucurbitaceae). Environ. Sci. Tech. 28:1110-1115.

Jones, K. C., and A. P. Sewart. 1997. Dioxins and furans in sewagesludges: a review of their occurrence and sources in sludge and oftheir environmental fate, behavior, and significance in sludge-amended agricultural systems. Critical Reviews in EnvironmentalScience and Technology 27:1-85.

Hulster, A., and H. Marschner. 1993. Transfer of PCDD/PCDF fromcontaminated soils to food and fodder crop plants. Chemosphere27:439-446.

Juttner, I., B. Henkelmann, K.-W. Schramm, C. E. W. Steinberg, R.Winkler, and A. Kettrup. 1997. Occurrence of PCDD/F in dated lakesediments of the Black Forest, Southwestern Germany. Environ. Sci.Technol. 31:806:812.

Muller, J. F., A. Hulster, O. Papke, M. Ball, H. Marschner. 1994. Transferof PCDD/PCDF from contaminated soils into carrots, lettuce andpeas. Chemosphere 29:2175-2181.

Safe, S. 1990. Polychlorinated biphenyls (PCBs), dibenzo-p-dioxins(PCDDs), dibenzofurans (PCDFs), and related compounds:environmental and mechanistic considerations which support thedevelopment of toxic equivalency factors (TEFs). Critical Reviews inToxicology 21:51-88.

Takizawa, Y. S. Asada, H. Muto. 1994. Dioxins in dust fall and volcanicash samples from the active volcanos Fugendake and Sakurajima.Organohalogen Compounds 20:359-362)

Washington Department of Ecology. 1998. Facts Sheet: ControllingMetals and Dioxins in Fertilizers. Publication #98-1251-HWTR,Washington Department of Ecology, Olympia, WA.

Yake, B., S. Singleton, and K. Erickson. 1998. Washington State DioxinSource Assessment. Publication No. 98-320, Washington StateDepartment of Ecology, Olympia, WA.




Cholinesterase testing can identify workers who,because of previous overexposure to organophos-phates (OPs), are at increased risk of subsequentpoisoning by these insecticides. Monitoring bloodcholinesterase levels has traditionally involved draw-ing blood samples at a hospital or clinic and sendingthem to a laboratory for evaluation. Results can takeas many as five days, during which time an at-riskworker may continue to be exposed.

In order to avoid such potentially dangerous delays,test kits designed to measure blood cholinesterase inthe field have been developed. Unfortunately thesekits have not been extensively tested in the field, andlittle is known about their performance compared tostandard laboratory methods.

Dr. Matthew Keifer, co-director of the Pacific North-west Agricultural Safety and Health Center, along withother researchers at the center, has been developingand evaluating procedures and methods for fieldtesting blood cholinesterase levels. Part of thisresearch has involved evaluating the accuracy of theEQM Testmate OP Kit™. (Ed. Note: The EQMTestmate OP Kit was the only kit tested. This report isintended to provide general information, and is notintended as an endorsement for this particular brandof field-test kit.)

Cholinesterase PhysiologyCholinesterase, or more properly acetylcholinest-erase, is an enzyme essential for normal functioningof the nervous system. In the body, acetylcholinest-erase inactivates the chemical messenger acetylcho-line, which is active at the junctions between nervesand muscles, between many nerves and glands, andat the synapses between certain nerves in the centralnervous system.

Acetylcholinesterase is present in both red blood cellsand plasma. The red blood cell acetylcholinesterateis also called rbc cholinesterase or erythrocyte cho-linesterase and is commonly identified as AChE. Theplasma cholinesterase, also called pseudocholinest-erase or butyrylcholinesterase, as well as just cho-linesterase, is commonly identified as PChE.

Cholinesterase Field-Test KitShows Good Potential

Norm Herdrich, Pacific Northwest Agricultural Safety & Health Center

OP and carbamate insecticides are cholinesterase(ChE) inhibitors, affecting the enzyme’s function bothat the nerve endings and in the blood. When cho-linesterase is inhibited significantly, the nervoussystem malfunctions. Affected individuals may exhibitpesticide-poisoning symptoms such as fatigue,lightheadedness, nausea, vomiting, and headaches.Severely low levels can result in death.

Kit TechnologyThe activity level of cholinesterase is an indication ofhow much exposure to OP and carbamate insecti-cides workers have received.

The field-test kit evaluated by Dr. Keifer and hiscolleagues uses a light-emitting diode to measure theconcentration of a chemical indicator that increases inproportion to the activity of cholinesterase in thesample being tested. Results are immediate andtesting is simple and inexpensive. The kit can beused to analyze blood drawn from the vein or capillaryblood obtained using a simple finger-stick. It canmeasure both PChE and AchE, and automaticallycorrects for hemoglobin levels that can affect theaccuracy of the test.

Research MethodologyThe objective of the testing was to determine if a field-based kit, by providing immediate, on-site data, couldfacilitate more timely removal of overexposed work-ers, and if the kit was sufficiently accurate to be usedas a substitute for lab testing. The three-year studyinvolved eighty orchard workers in six eastern Wash-ington orchards in the Yakima Valley and Tri-Citiesareas who had regular exposure to Guthion, Diazinonand several other organophosphate and n-methylcarbamate insecticides.

The blood levels of the test group were compared tothose of a control group of twelve workers with noknown exposure. The results obtained using the field-test kit were compared to the findings of the Washing-ton Department of Health (WDOH) laboratory for bothPChE and AChE levels. Urine was also monitored fororganophosphate breakdown products.


The first specimens were obtained about three weeksbefore the start of the spraying season to determinebaseline cholinesterase levels. Three follow-up speci-mens were analyzed during the spraying season todetermine if added exposure to the insecticidescaused depressed cholinesterase levels. These testswere timed to coincide as closely as possible withpesticide applications in the participating orchards.

Analysis of urine samples from some of the workersconfirmed that exposure was occurring, but no signifi-cant changes in ChE levels were noted using eitherthe laboratory testing or the field-based methods.

The correlation of PChE and AChE measurementsrecorded by the kit and those recorded by the WDOHlaboratory were quite high. In fact, according to Dr.Keifer, the experiments suggest the kit may measureAChE even more accurately than the laboratory.

Part of the research by Dr. Keifer and his associatesevaluated the differences in ChE levels betweenblood obtained using the finger-stick method, whichdraws blood from capillaries, and blood drawn from avein. This was done to determine if skin contamina-tion with pesticides might give falsely low values whenfinger stick methods were used. On average, theblood from the finger-stick showed slightly lower ChElevels than did blood drawn from the vein. Dr. Keifersays that although the difference between theselevels was statistically significant, it was very smallrelative to the amount of activity change currentlyconsidered to be critical, and because of this shouldnot be viewed as clinically significant.

“However,” Dr. Keifer adds, “this study data adds tothe evidence that skin contamination from pesticidesmay be a source of error in capillary-based testing,and that attention to hand washing or other skin-cleaning methods is necessary to assure accurateresults.”

Another finding of the study was that the cholinest-erase levels reported by the field-test kit could be

affected by temperature. While the kit had an internalprogram to adjust results for changes in temperature,this program did not appear to adjust the resultsenough to allow testers to disregard temperaturecompletely. (During the field-testing phase of thestudy, the testing environment was always within anarrow temperature range, and this avoided undueinfluence of temperature on the field results.)

Field-Test ResultsDr. Keifer’s study found a limited range of cholinest-erase values among the workers tested. Because thevalues were in the normal range for humans, thereappears to have been relatively little heavy exposureto pesticides, Keifer notes.

“While this was excellent news for the workers, thelack of heavy exposure prevented us from determin-ing how the field-test kit performs across a wide rangeof values. As a result, we can say little about how thekit performs when values are very low in workerstested in the field.”

One unexpected finding of Dr. Keifer’s study was thatquality control for red blood cell cholinesterase testingat the WDOH laboratory was problematic. Resultsfrom the laboratory were difficult to interpret and didnot match those obtained with the kit. Since theresults from the kit were more consistent with theexposure scenario than the results from the labora-tory, blinded spiked samples were sent to thelaboratory. When kit and lab results from the spikedblood samples were compared side by side, theresults from the kit appeared to better reflect theknown pesticide content of the spiked samples. While only a single laboratory was used for compari-son to the kit throughout the study, results from astudy conducted by the Environmental ProtectionAgency indicate that methods commonly used bycommercial laboratories across the country may giveimprecise results.

“Based on the results of our study and those of theEPA study, I am not certain the methods commonly

Cholinesterase Field-Test Kits, cont.




used by many commercial laboratories are capable ofproviding reliable results,” concludes Dr. Keifer.

He goes on to explain that there has been no system-atic effort to standardize cholinesterase testing val-ues. “Unlike many common laboratory tests whichhave quality assurance programs, no systems are inplace to assure quality for cholinesterase testing.”

Current Industry Testing andPotential Application of Field TestingIt is widely held that workers frequently exposed toOP and carbamate insecticides should be in a cho-linesterase testing and monitoring program.

In fact, the state of California has required cholinest-erase monitoring since 1974 for all workers with morethan a specified amount of exposure to Class I or IIOPs or n-methyl carbamates. The objectives of theCalifornia program are to be able to remove overex-posed workers from exposure situations, to identifyand intervene in high-risk work behaviors, to helpdecide when the exposed worker can safely return towork, to raise awareness of the toxicity of thesepesticides among employers and workers, and toprevent chronic health effects from exposure to thecholinesterase-inhibiting materials.

Field-test kits are not currently in widespread use inCalifornia. Most growers use commercial laboratories.“(California labs have) probably worked out the bugsmore completely than the labs (in Washington),”concedes Dr. Keifer, “because they have been doing itfor a lot longer.”

Should cholinesterase monitoring be required inWashington? Dr. Keifer points out that such a pro-gram imposes a substantial economic burden ongrowers. But if pesticide poisonings are avoided, asubstantial personal and economic burden is avoidedfor both the grower and the worker. Also, he addedthat orchardists in Washington do not appear to useinsecticides as much or as long as growers inCalifornia.

In California, testing is required only for workers whowork with Class I and II OPs or carbamates for six ormore days in a thirty-day period. By spreading out theapplication duties among several trained workers,individual exposure days can be reduced, thus avoid-ing testing under these parameters.

ConclusionsSo what’s the bottom line for field-test kits? “Undervery restricted conditions, (the tested kit) providespotentially valuable information about exposure tocholinesterase-inhibiting substances in an inexpen-sive and efficient way,” says Dr. Keifer. The restrictedconditions include the establishment of a standardagainst which to compare the results, and using thekit within a relatively narrow temperature range. (Anew version of the Testmate kit is now available whichclaims to have solved the temperature variabilityproblem. Dr. Keifer says the PNW Agricultural Safetyand Health Center is testing one of the new kits.Other improvements to the newer kits include provid-ing sample buffer bottles that permit a field-drawnsample to be transported to a distant location withoutdrying out.)

“Potentially,” Dr. Keifer concludes, “the Testmate kitis a good tool. It has some real potential, partlybecause it uses proven methodology to conduct the tests.”

The Pacific Northwest Agricultural Safety and HealthCenter, funded by NIOSH, is one of eight such cen-ters in the United States. The Center’s mandate is tostudy occupational health and safety issues in farm-ing, forestry and fishing in the four Region Χ states ofIdaho, Washington, Oregon and Alaska. Dr. RichardFenske is the Center Director, Dr. Matthew Keifer isCo-Director, and Sharon Morris is Associate Director.Adrienne Hidy is the Center’s Administrator. Thisarticle was prepared by Norm Herdrich, PNASHOutreach Coordinator. To obtain additional informa-tion, he can be contacted at (509) 926-1704 [email protected].


Cholinesterase Field-Test Kits, cont.


Dr. Carol Weisskopf, Analytical Chemist, WSU

Is produce marketed as having “no pesticides de-tected” actually free of pesticides? Are organic fruitsand vegetables free of pesticides? Would an increasein the number of commodities in which pesticideswere detected indicate that our food supply wasbecoming increasingly contaminated? If you weregoing to buy a used car, and the dealership told youthat they found no defects in their examination, wouldyou look under the hood anyway?

Most people have a much better idea of the workingsof an automobile than of pesticide residue chemistry.At least they know there should be an engine in theresomewhere, and that the usual number of wheels isfour. In evaluating our fruits and vegetables beforewe buy or eat them, we’re not so self-reliant—noteven chemists have a gas chromatograph in thegarage to test the pesticide content claims of the localsupermarket. Fortunately, if we want to examine thepesticide content of our food supply, ample data areavailable.

The problem is not with data, but with its use andinterpretation. A literature review illuminates an ever-growing problem with pesticide-related issues: pesti-cide detection limits are getting lower. What at firstappears to be an advantage—better science resultingin lower detection limits—becomes a problem whenthe prevailing perception is that detections are, ofthemselves, related to safety. As detection limits getlower, instances of residue detection on crops in-creases. We are gradually approaching the analyticalcapability to detect pesticides in 100% of samplesanalyzed. The time has come to move toward foodsafety regulations based on concentrations of pesti-cides, not simple detection of them.

Free? Unlikely.

Data: Available and VariedIn-depth data has been compiled by the U.S. Foodand Drug Administration (FDA, http://vm.cfsan.fda.gov) and by the California Department ofPesticide Registration (CDPR, http://www.cdpr.ca.gov). Both agencies monitor fruits andvegetables for violations of pesticide tolerances,“tolerance” being defined as the maximum pesticideconcentration allowed in a commodity for which aregistration exists. Detections of a pesticide on a cropfor which there is no registration, and thus no toler-ance, are also considered violations. Violations ofeither type can result in removal of the commodityfrom commerce. Because shipments from whichsamples are collected may be held until analyses arecompleted, these programs rely on rapid analysismethods with detection limits adequate for detectionof pesticide concentrations in the vicinity of tolerances.

At the other end of the spectrum is the rigoroustesting conducted by the U.S. Department of Agricul-ture Pesticide Data Program (PDP, http://www.ams.usda.gov/science/pdp/index.htm). ThePDP is not under the time constraints of the FDA andCDPR surveillance sampling, as the PDP does notaffect commodity distribution. The PDP strives for thelowest detection limits, which can require analysistimes of weeks, rather than hours.

Summary data from FDA, CDPR, and PDP are pre-sented in Table 1. The most recent available FDA dataare from 1997, and for CDPR from 1995. PDP’s mostrecent available data are from 1996. In each case,both imported and domestic fruits and vegetableswere tested.

TABLE 1: ANALYSES OF PESTICIDES IN FRESH FRUITS AND VEGETABLES

Commodity Number of Number of Samples with Samples over Detections withProgram Types Sampled Analytes Samples Detections Tolerance No Tolerance

FDA 70 366 7,268 39% 0.36% 1.4%

PDP 8 77 3,618 74% 0.22% 4.5%

CDPR 132 200 5,502 35% 0.31% 1.3%




As might be expected, the FDA and CDPR data showsimilar percentage instances of pesticide detectionsand tolerance violations. The PDP data, also unsurpri-singly, show a higher percentage of samples withdetections and a higher percentage of detections ofproducts for which no tolerance has been established.

Detections: We Can FindSomething in Everything. So What?If the number of pesticide detections were a directmeasure of food safety, one could conclude that thesamples analyzed by FDA and CDPR, with 35 and39% detection rates, were twice as safe as thoseanalyzed in the PDP, at 74% detections. In actuality,the difference is simply a demonstration of the impactof analytical methods with low detection limits.

A basic tenet of toxicology is that“the dose makes the poison.” Itis the concentration that deter-mines exposure level, and thusimpact, not the simple occur-rence. Unfortunately, detectionsthemselves are often used incomparisons of food safetyregardless of concentrations,and are considered undesirablein and of themselves by thepublic and some regulators.

Which leads to the issue of detection of pesticides notregistered for use on the commodity on which theyare detected. In the PDP data, 4.5% of the samplescontained such residues. PDP used twelve laborato-ries for their analyses. If the data were reassessed asif each pesticide/crop combination had been analyzedby the PDP lab with the least sensitive procedure, thetotal number of detections would drop only from 74 to70%. But, the unregistered use detections woulddrop from 4.5 to 1.5%. If two thirds of such detectionsare eliminated using the worst detection limits, wouldapparent violations triple if the best were used?

It is long past time to disconnect detection capabilityfrom assumption of hazard.

The Real Issue: Evaluating RiskWhen a chemist can find just about everything in justabout anything, the concept of “pesticide-free” food or,for that matter “anything-free” food, becomes irrel-evant. It might be useful simply to stipulate that we candetect at least one pesticide in any sample, and get onwith the business of deciding what the data mean.

The tolerance should be considered as the touch-stone for risk evaluation, with debate centering on theadequacy of existing and proposed tolerances.

But what of “unregistered use” violations—those forresidues found on a crop for which there is no regis-tration or label, and thus no tolerance? Such detec-tions account for the majority of violations found. In

these cases, it is simple detection,rather than concentration, thatconstitutes a violation. Again, theefforts should center on the estab-lishment of risk criteria. Onesolution would be to expand theuse of action limits.

DDT, although no longer regis-tered in the United States, remainsin the environment. DDT or itstransformation products can still

be detected at trace levels on commodities. Actionlimits have been established for DDT and other now-banned chlorinated insecticides, which function as defacto tolerances. Concentrations below these limitsare considered acceptable, while those above resultin the same market restrictions as over-tolerancefindings. In the PDP data, 378 detections were ofcompounds in this class; none was found over theaction limit.

Perhaps we should also stipulate that improvinganalytical capabilities will eventually result in detectionof some level of unregistered agent on 100% ofsamples. Since this seems inevitable, we should dealwith this issue before we run out of food that is legalto bring to market.

It is long past timeto disconnect

detection capabilityfrom assumption

of hazard.

…Free? Unlikely. (cont.)Dr. Carol Weisskopf, Analytical Chemist, WSU


Detections With No Tolerance:Ethics and SemanticsDespite the terminology, many “unregistered use”residues are the result of the physical and chemicalbehavior of pesticides rather than the intentional useof an unlabeled pesticide by a grower. Drift, croprotations, packing conditions, post-harvest process-ing, and transport of pesticides in air, rain, fog, or dustcan all give rise to low but detectable residues.When I used to perform pesticide enforcement analy-ses, I enjoyed ferreting out concentrations of unla-beled pesticides at levels indicating an inappropriateapplication. However, when I detected pesticides atextremely low levels—concentrations easily attribut-able to environmental redistribution—this alwayspresented an ethical, rather than analytical, dilemma.There is a difference, in intent as well as in concentra-tion, between willful application of an unregisteredpesticide and inadvertent receipt of a pesticide resi-due through fog or dust.

As detection limits improve, this dilemma will in-crease. Should a handful of wayward molecules beconsidered a violation? It is difficult producing gooddata for enforcement of regulations you believe areoutdated. This has bothered me for 15 years, and weseem no closer to a solution.

“Inadvertent residue” is a much more accurate termthan “unregistered use” for many detections. I firstheard this term in the 1980s from my doctoral researchadvisor, Dr. Jim Seiber, in his studies of pesticidetransport in fog. If we remove the connotation of will-fulness from these occurrences, perhaps they can beevaluated more rationally and regulated appropriately.

While the regulatory, chemical, and producer commu-nities are in the throes of tolerance readjustmentsubsequent to enactment of the FQPA, it would bepractical, efficient, and useful to at the same timeestablish action limits based on toxicological ratherthan analytical criteria, regulating unlabeled applica-tions and allowing inadvertent residues. Pesticidechemists could then pursue the goals of better analy-sis methods, more sensitive laboratory equipment,

and ever-decreasing detection limits without worryingabout the impact on growers when dozens or hun-dreds of unregistered molecules are detected.

Organic Produce, “No PesticidesDetected” Produce, & Marketing ClaimsThe final data set is from a study conducted by Con-sumers Union (CU), and described in the January1998 issue of Consumer Reports. Although fewdetails of the sampling and analyses are given, CUcollected about 170 fresh produce samples from 4commodities, and had them analyzed for over 300pesticides.

Both the PDP and CU data included results fromsamples labeled as organic. In addition, the PDPsamples contained a few for which claims of “nopesticides detected” had been made. (Such claimsgive no indication of the sensitivity of methods used ornumber of pesticides included in the analyses.) TheCU samples also included a category they referred toas “green,” which are commodities for which someclaims were made of environmental friendliness intheir production.

The number of samples from each category in the CUdata is not given, but an even distribution among thethree tested categories would be expected in a studydesigned to compare them. CU and PDP both re-ported pesticide detections and tolerance violations(Table 2). The most amusing part of these data is thatthe produce with “no detected residue” claims actu-ally had a higher proportion of detections than anyother category. Given the small number of sampleswith this claim, the difference is unlikely to be statisti-cally significant.

The CU and PDP data are in close agreement (77and 74%) on the proportion of detections in thesamples for which no claims were made. On the otherhand, the organic samples analyzed show quite adifference in detections, with CU finding residues in25% and PDP having no detections. The limitednumber of organic PDP samples and the small num-ber of commodities included in either data set may


...continued on back page


contribute to the differ-ence, as might the in-creased number of pesti-cides screened in the CUanalyses. Both data setsshow considerably fewerdetections in samples withorganic labels, with anintermediate level ofdetections in the CU“green” samples.

One of the CU organicsamples contained apesticide concentrationabove that considered acceptable for designation asorganic produce. One accepted criterion allowsconcentrations up to 5% of the established tolerancein commodities with the organic designation. Suchcriteria acknowledge inadvertent residues, rather thancondoning use of synthetic pesticides by organicgrowers.

CU also generated a “toxicity score” for their report,using the pesticide identities and concentrationsfound. The CU report included the caution that botani-cal extracts and metallic compounds accepted inorganic production can be as toxic as traditionalpesticides. However, these alternatives to syntheticpesticides were not included in CU’s chemical analy-ses, and so were not considered in generation of the“toxicity score”. Produce with an organic label hadlower computed overall toxicity, although omission ofresidue data for non-synthetic pest control agentsmakes the comparison moot. Although organicproduce was designated as “least toxic,” such termi-nology does nothing to improve my appetite.

We would do well to remember that organic farming ismore than a method for delivering reduced-pesticideproduce to the consumer, and detections are not theonly measure of its value. It can also be an ethic, aphilosophy, and a way of living in the environment, aswell as a marketing tool.

Getting Real: Serving andProtecting the ConsumerConsumers want to buy safe produce. Throughmarketing, consumers have been educated to equate“no pesticide” with “safe.” But claims of “no detectedresidue,” while viewed by some as providing con-sumer information, may speak more to low-qualitydetection limits than high-quality comestibles. ThePDP data indicate such a designation is considerablyless predictive of pesticide detection than is theorganic labeling, yet such claims may become com-monplace when the FQPA-mandated brochure ap-pears in supermarkets.

Even organic produce, while performing well bycomparison to unlabeled and “no residues”-labeledproduce in the PDP test, cannot promise “no pesti-cides.” Wind, rain, fog, and dust can transport pesti-cides at levels sufficient to result in detections. Andthe rain, along with any trace levels of pesticides itmay contain, falls equally on the organic and the non-organic grower. If the best CU can do is call organicsamples the “least toxic,” such unfortunate terminol-ogy proves a disservice to the organic and the non-organic grower alike, not to mention the consumer.

Analytical techniques are becoming more sophisti-cated and detection limits are decreasing in response

TABLE 2: ANALYSIS OF PESTICIDES IN FRESH FRUITS ANDVEGETABLES BY MARKETING CLAIM

Number of Number of Samples with Samples over Detections withProgram Claim Samples Commodities Detections Tolerance No Tolerance

PDP none 3,600 8 74% 8 (0.16%) 163 (4.5%)

PDP organic 10 4 0% 0 0

PDP no residues 6 3 83% 0 0

CU none 50 - 60 4 77% 0 1 (2%)

CU green 50 - 60 4 55% 0 0

CU organic 50 - 60 4 25% 1*(2%) 0

* concentration above criteria for organic produce eligibility, not above legislated tolerance.

...continued on back page



to the need to provide more accurate risk assess-ments, deal with lowering tolerances, and prepare forthe next generation of pesticide chemistries. Establish-ing tolerances, analyzing for tolerance compliance,and depending upon detection limits are only parts ofthe picture. Like an iceberg, much is below the sur-face.

Most of us sprinkle our gardens with water that meetsthe drinking water standards, but may contain pesti-cides at trace levels. If these pesticide levels weredetectable, garden watering could be considered atolerance violation. This is an example of why actionlimits should be instituted for inadvertent residues.

Although consumers may want to be able to buyproduce without pesticides, it is impossible even fororganic growers to deliver it. But the pesticide contentof our food is well below levels considered accept-able. We have one of the most abundant, inexpen-sive, and safe food supplies in the world. There is noreason to dust off your gas chromatograph and testfood before you eat it. But if your local supermarketstarts to offer produce with “no detected residues,”kick the tires before you buy.

Dr. Carol Weisskopf is an Environmental Chemist atWSU. She can be reached at (509) 372-7464 or [email protected].

…Free? Unlikely. (cont.)

Tolerance Information


TOLERANCE INFORMATIONTime-LimitedChemical

(type)FederalRegister

Tolerance(ppm)

Commodity (raw)

Yes/No New/Extension Expiration Datealder bark residue 10/5/98 page 53291 exempt see comment No N/A N/AComment: This exemption applies when alder bark residue is used as an inert ingredient (seed germination stimulator) in pesticideformulations applied to growing crops.

pyridaben 10/5/98 page 53294 0.75 cranberries Yes New 12/31/99Comment: This time-limited tolerance is issued in response to EPA granting a Section 18 for the use of pyridaben to control southern red mitein Massachusetts' cranberries.

avermectin (insecticide) 10/7/98 page 53825 0.05 basil Yes Extension 1/31/00Comment: This time-limited tolerance is extended in response to EPA granting a Section 18 for the use of avermectin to control leafminers inCalifornia basil.

bifenthrin (insecticide) 10/7/98 page 53818 0.50 canola Yes Extension 3/30/00Comment: This time-limited tolerance is extended in response to EPA granting Section 18's for the use of bifenthrin to control aphids in canolain Oregon, Washington, and Idaho.


Dr. Carol Weisskopf, Analytical Chemist, WSU


fludioxonil (fungic ide) 10/7/98 page 53820 0.01 brassica, leafy vegetable No N/A N/A0.02 bulb vegetables0.02 cereal grains0.01 cucurbit vegetables0.01 legume vegetable; foliage0.01 cereal grains; forage,

fodder, and straw0.01 fruiting vegetables except

cucurbits0.01 grass; forage, fodder and

hay0.02 herbs and spices0.01 legume vegetables0.01 non-grass animal feeds0.01 rape; forage and seed0.02 root and tuber vegetables0.01 sunflower seed

imidacloprid (insecticide) 10/7/98 page 53826 0.30 beet root Yes Extension 6/30/000.30 turnip root3.50 turnip top

Comment: This time-limited tolerance is extended in response to EPA granting a Section 18 for the use of imidacloprid to control green peachaphid in California beet and turnip crops.

pyridate (fungicide) 10/7/98 page 53837 0.10 chickpea No N/A N/A

tebuconazole (fungicide) 10/7/98 page 53813 0.20 sunflower seed Yes Extension 9/30/990.40 sunflower oil

Comment: This time-limited tolerance is extended in response to EPA granting Section 18's for the use of tebuconazole to control rust insunflower crops in North Dakota, Kansas, Colorado, and Nebraska.



Tolerance(ppm)

Commodity (raw)

Yes/No New/Extension Expiration Date

sethoxydim (herbicide) 10/8/98 page 54066 0.20 apricot No N/A N/A0.20 cherry0.20 nectarine0.20 peach

15.00 bean; forage andsucculent

16.00 soybean1.00 grape2.00 raisin4.00 cilantro4.00 leafy vegetable crop

group (except Brassica)4.00 tuberous and corm

vegetable subgroup1.00 garden beets5.00 cranberry crop subgroup5.00 globe artichoke


…Tolerance Information, cont.Jane M. Thomas, Pesticide Notification Network Coordinator, WSU




Tolerance(ppm)

Commodity (raw)

Yes/No New/Extension Expiration Date

…Tolerance Information, cont.

cyromazine (insecticide) 10/9/98 page 54360 0.05 turkey; meat, fat, andmbp

Yes Extension 4/1/00

Comment: This time-limited tolerance is extended in response to EPA granting Section 18's for the use of cyromazine to control flies onturkeys in North and South Carolina.

mancozeb (fungicide) 10/9/98 page 54362 2.00 ginseng Yes New 12/31/99Comment: This time-limited tolerance is established in response to EPA's granting a Section 18 for the use of mancozeb to control leaf andstem blight in ginseng grown in Wisconsin.

paraquat 10/9/98 page 54357 0.30 dry peas Yes Extension 5/15/00(herbicide/desiccant/defoliant)Comment: This time-limited tolerance is extended in response to EPA granting Section 18's for the use of paraquat to control weeds in drypeas grown in North Dakota, Montana, Idaho, Washington, and Oregon.

dimethomorph (fungicide) 10/13/98 page54587

0.05 potatoes No N/A N/A

hexythiazox (insecticide) 10/13/98 page54594

2.00 hop Yes New 9/15/00

3.00 strawberryComment: This time-limited tolerance is established in response to EPA granting Section 18's for the use of hexythiazox on Californiastrawberries and on hops grown in Washington, Oregon, and Idaho.

azoxystrobin (fungicide) 10/16/98 page55533

0.03 potatoes Yes New 10/18/99

Comment: This tolerance was requested by Wisconsin potato growers, University extension specialists, Zeneca, and EPA in an effort to gatherdata to support registration of a reduced-risk fungicide.

hexythiazox (insecticide) 10/16/98 page55540

2.00 dried hops No N/A N/A

Miscellaneous InformationOn October 9, 1998, EPA announced that, in response to FQPA requirements, the agency had established a policy in conjunction with the FDAthat 1) established interpretations of the FFDCA as they relate to jurisdiction of EPA and FDA overantimicrobial substances used in food; 2) discussed interpretation of certain terms in FIFRA relevant to the authority of the two agencies; 3)described how EPA and FDA propose to clarify the post-FQPA regulatory authority over certain antimicrobialsubstances; and 4) discussed how EPA and FDA plan to handle the review of petitions for antimicrobial substances that will remain under EPAjurisdiction and for those that EPA proposes to return to FDA's authority. (10/9/98 page 54532)

On October 20,1998, the Agricultural Marketing Service announced that it is proposing to revise the Federal Seed Act (FSA). The proposedchanges include prohibiting shipment of agricultural and vegetable seeds containing seeds of noxious weeds, addingtwo kinds to the list of those subject to the FSA, and updating the seed testing and certification regulations. (10/20/98 page 55964)

In the October 29 Federal Register, EPA announced a schedule for issuance of a series of scientific policies that will be used to comply with theprovisions of the Food Quality Protection Act. (10/29/98 page 58038)



The PNN is operated by WSU’s Pesticide Information Center for the Washington State Commission on Pesti-cide Registration. The PNN system is designed to distribute pesticide registration and label change informa-tion to groups representing Washington’s pesticide users. The material below is a summary of the informationdistributed on the PNN in the past month.

Our office operates a web page called PICOL (Pesticide Information Center On-Line). This provides a labeldatabase, status on registrations and other related information. PICOL can be accessed on URL http://picol.cahe.wsu.edu or call our office, (509) 372-7492, for more information.

PNN UpdateJane M. Thomas, Pesticide Notification Network Coordinator, WSU

Federal Issues

Section 18 Specific ExemptionsOn September 30, 1998, EPA issued a Section 18specific exemption for the use of Gramoxone Extra fordesiccation of weeds in green peas grown for seedand dry pea fields. This exemption is for use on16,758 acres and expires November 30, 1998. Notethat the exemption also contains Water Howellia(Spokane county) protection directions.

On October 1, 1998, EPA issued a Section 18 specificexemption for the use of Maverick to control downybrome in wheat. The exemption is for use on1,544,000 acres and expires 10/1/99. EPA issued anamendment to this Section 18 on October 6, 1998, tonow include use in Benton County. Growers shouldbe aware that even though this exemption restrictsuse to ground applications, the requirements of WAC16-230-800 through 870, “Rules Relating to Applica-tion of Pesticides in Benton County and Portions ofFranklin and Walla Walla Counties,” do apply. Copiesof this rule are available from WSDA by calling (509)575-2746 or (360) 902-2040.

Supplemental Labels and Use RecommendationsBayer has issued a use recommendation for the useof Sencor DF or Sencor Solupak on winter wheat.The product bulletin provides direction for a splittingthe Sencor application into two treatments, providedcertain conditions are met, in order to increase cropsafety, improve coverage, and increase weed control.

Bayer has issued a supplemental label for its insecti-cide Provado 1.6 Flowable. The supplemental labeladds direction for controlling San Jose Scale in

apples as well as adding crabapple, pear, and quinceuse directions.

Miscellaneous Regulatory InformationNote: The purpose of the following PNN notifica-tions was to make members of Washington’s agricul-tural community aware of certain inquires that hadbeen made by USDA. In each case USDA was askingfor information based on an initial inquiry from EPA.The information was distributed on the PNN becauseit may indicate the direction of future regulatoryaction.

USDA’s Office of Pest Management Programs re-quested that certain states gather information on thepossible impact to the strawberry industry if the phi foriprodione was changed from 0 to restrict the use to“first flowering.” Iprodione is registered for use onstrawberries in Washington under four labels; all areRhone Poulenc: Rovral, Rovral 4, Rovral 50SP, andRovral WG. WSU made inquiries of appropriateextension specialists and passed along the followinginformation to USDA:

First, If iprodione is restricted to prebloom application,it will become unusable to the strawberry industry.Growers need to have Rovral as a option at least forthe first application at 5 to 10% bloom.

Second, The status of alternatives to Rovral is asfollows:

Captan - is effective and has little risk for developingresistance. The PHI is 3 days. Use of this productwithout the availability of iprodione and its 0-day PHIwill alter grower’s picking schedule.



Benlate & Topsin M - not effective due to resistance.

Ronilan - manufacturer is in the process of voluntarilydeleting strawberries from all product labels.

Thiram - not as effective as captan but useful formanaging resistance; however, Whatcom countygrowers have no experience with thiram.

USDA’s Office of Pest Management Programs alsorequested that certain states gather information onthe possible impact to the stone fruit industry if the phifor iprodione was changed from 7 days to either 45 or90 days. Iprodione is registered for use on stone fruitin Washington under four labels; all are RhonePoulenc: Rovral, Rovral 4, Rovral 50SP, and RovralWG. WSU made inquiries of appropriate extensionspecialists and passed along the following informationto USDA:

Changing the phi to 45 or 90 days will preclude usingiprodione for the fruit rot phase of brown rot (thephase of most concern); however, effective alternateproducts do exist. Therefore, changing the iprodionephi to either 45 or 90 days will have little impact onWashington’s stone fruit production.

USDA’s Office of Pest Management Programs re-quested information on the possible impact of banningthe use of aluminum or magnesium phosphide within500 feet of any occupied (working or living) structure.Both aluminum phosphide and magnesium phosphideare typically used to fumigate grain or other commodi-ties in storage or transit or to fumigate empty agricul-tural containers. Other registered uses in Washingtoninclude use to fumigate rodent burrows or bee hives.WSU made inquiries of a commercial pest controlcompany that specializes in food processing, export,and warehousing applications. The following informa-tion was passed on to USDA:

Imposing a 500 foot buffer zone around phosphinefumigations would severely restrict the use of theseproducts. Because of the pending loss of methylbromide, after January 1, 2001, phosphine will be the

…PNN Update, cont.


only fumigant registered for use on food commodities.Currently EPA lists aluminum phosphide and magne-sium phosphide as alternatives for methyl bromide.Restricting phosphine use via the imposition of abuffer zone will severely limit agriculture’s ability tofumigate stored commodities.

In almost no cases will a 500 foot buffer zone existwhere fumigation of shipping containers and trucktrailers are concerned. In-transit fumigation of storedcommodities will not be possible with a buffer zonerequirement. Not only will this restriction impactcommodities being handled within the US it will alsomake it difficult to meet the import requirementsimposed by other countries.

The final comment passed along to USDA questionedwhether off-site exposure is a valid concern.

State Issues

New RegistrationsWSDA has registered Sureco’s insecticide All ProDiazinon 50 WP. This product is registered for use onthe following PNN-related sites: apple, apricot, beet,blackberry, boysenberry, broccoli, Brussels sprout,cabbage, caneberries, cantaloupe, carrot, cauliflower,cherry, Chinese broccoli, Chinese cabbage, Chinesemustard, collard, conifer, corn, cranberry, cucumber,deciduous/shade tree, dewberry, ditch bank, dry bulbonion, endive, evergreen tree, grape, green bean,green onion, green pea, honeydew, hop, kale, lettuce,lima bean, loganberry, melon, mushroom house,muskmelon, mustard, nectarine, non-dairy livestockbuilding, ornamental, ornamental tree, parsley, pars-nip, pea, peach, pear, pepper, plum, potato, prune,radish, raspberry, rose, sheep, shrub, spinach, straw-berry, sugarbeet, summer squash, sweet corn, sweetpotato, Swiss chard, tomato, turnip, watermelon, andwinter squash.

WSDA has issued a registration to Griffin Corp. for itsinsecticide Declare. This product is registered for useon the following sites: alfalfa, barley, beet, broccoli,Brussels sprout, cabbage, canola, cauliflower, celery,



clover, collard, corn, dry bean, green bean, kale,lettuce, oat, pasture, pea, potato, rye, soybean,spinach, sugarbeet, sweet potato, vetch, wasteland,and wheat.

WSDA has registered Platte Chemical’s herbicideTrifluralin HF. This product is registered for use onthe following sites: alfalfa, apricot, asparagus, barley,broccoli, Brussels sprout, cabbage, carrot, cauliflower,collard, corn, dry bulb onion, flax, green bean, hop,kale, lima bean, mustard, nectarine, okra, pea, peach,pepper, plum, potato, prune, radish, soybean,sugarbeet, sunflower, tomato, vineyard, walnut, andwheat.

WSDA has registered Nichimen America’s fungicideKaligreen. This product, which is used for powderymildew control, is registered for use on the followingsites: cucumber, grape, rose, and strawberry.

Section 24c RegistrationsOn September 24, 1998, WSDA took two actionsregarding SLN’s for the use of Supracide 25WP tocontrol grass scale, thrips, and spider mite in timothyand timothy-alfalfa stands grown for forage or hay.

First, WSDA issued a revision to SLN WA-940020.This SLN had previously been issued for the use ofNovartis’ formulation of Supracide 25WP, EPA Regis-tration Number 100-754. The revision includesadding a restricted use pesticide (RUP) statement,changes to the pollinator protection statement, andchanging the SLN number to WA-940020a. Novartisplans to transfer the Supracide registration to Gowanin the near future; however, this SLN will remain ineffect for at least another year.

Second, because Gowan will be taking over thisregistration, WSDA issued a second SLN, WA-940020b, to Gowan for their Supracide 25WP formula-tion, EPA Registration Number 100-754-10163. ThisSLN is virtually identical to the SLN issued to Novartis.

On September 29, 1998, WSDA issued an SLN, WA-980031, to Zeneca for the use of their herbicide


Fusilade DX to control downy brome, quackgrass,bentgrass, and volunteer cereals in fescue grassesgrown for seed. The SLN carries several restrictions:Fusilade DX may not be applied after fescue grassseedhead develops into the boot stage, no part of thegrass plants, including seed or seed screenings, is tobe used as a food or feed, and grass seed shall betagged to indicate it is not to be used for food or feed.This SLN expires December 31, 1998.

Section 24c RevisionsOn September 28, 1998, WSDA issued a revision toSNL WA-940034. This SLN had previously beenissued to Du Pont for the use of its insecticide AsanaXL to control root weevils on blueberries. The revi-sion includes significant changes to the pollinatorprotection statement.

On September 28, 1998, WSDA issued a revision toSLN WA-770040. This SLN had previously beenissued to Du Pont for the use of its product BenlateFungicide for preplant treatment of asparagus crowns.The revision includes updating the label use direc-tions.

On September 28, 1998, WSDA issued a revision toSLN WA-950047. This SLN had previously beenissued to Dow for the use of its herbicide Treflan HFPat layby to control weeds in onions. The revisionincludes removal of the expiration date and theaddition of a chemigation restriction statement.

On September 28, 1998, WSDA issued a revision toSLN WA-900016. This SLN had previously beenissued to Dow for the use of its herbicide Treflan TR-10 for dodder control in alfalfa seed crops. Therevision includes the addition of a chemigation prohi-bition.

On September 28, 1998, WSDA revised SLN WA-970033, removing the expiration date. This SLN hadpreviously been issued for the use of Dow’s herbicideStinger to control weeds in broccoli, cabbage, cauli-flower, Swiss chard, and beet seed.

…PNN Update, cont.

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