ENVIRONMENTAL CONTAMINANTS … p- (p-Xylene, para-xylene, CAS number 106-42-3) NOTE: The majority of...

ENVIRONMENTAL CONTAMINANTS ENCYCLOPEDIA

p-XYLENE ENTRY

July 1, 1997

COMPILERS/EDITORS:

ROY J. IRWIN, NATIONAL PARK SERVICE

WITH ASSISTANCE FROM COLORADO STATE UNIVERSITY

STUDENT ASSISTANT CONTAMINANTS SPECIALISTS:

MARK VAN MOUWERIK

LYNETTE STEVENS

MARION DUBLER SEESE

WENDY BASHAM

NATIONAL PARK SERVICE

WATER RESOURCES DIVISIONS, WATER OPERATIONS BRANCH

1201 Oakridge Drive, Suite 250

FORT COLLINS, COLORADO 80525

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Like a library or many large databases (such as EPA'snational STORET water quality database), this documentcontains information of variable quality from verydiverse sources. In compiling this document, mistakeswere found in peer reviewed journal articles, as well asin databases with relatively elaborate quality controlmechanisms [366,649,940]. A few of these were caughtand marked with a "[sic]" notation, but undoubtedlyothers slipped through. The [sic] notation was insertedby the editors to indicate information or spelling thatseemed wrong or misleading, but which was neverthelesscited verbatim rather than arbitrarily changing what theauthor said.

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It should be kept in mind that data comparability is amajor problem in environmental toxicology sincelaboratory and field methods are constantly changing andsince there are so many different "standard methods"published by EPA, other federal agencies, state agencies,and various private groups. What some laboratory andfield investigators actually do for standard operatingpractice is often a unique combination of variousstandard protocols and impromptu "improvements." Infact, the interagency task force on water methodsconcluded that [1014]:

It is the exception rather than the rule thatwater-quality monitoring data from differentprograms or time periods can be compared on ascientifically sound basis, and that...

No nationally accepted standard definitions existfor water quality parameters. The differentorganizations may collect data using identical orstandard methods, but identify them by differentnames, or use the same names for data collected bydifferent methods [1014].

Differences in field and laboratory methods are alsomajor issues related to (the lack of) data comparabilityfrom media other than water: soil, sediments, tissues,and air.

In spite of numerous problems and complexities, knowledgeis often power in decisions related to chemicalcontamination. It is therefore often helpful to be awareof a broad universe of conflicting results or conflictingexpert opinions rather than having a portion of thisinformation arbitrarily censored by someone else.Frequently one wants to know of the existence ofinformation, even if one later decides not to use it fora particular application. Many would like to see a highpercentage of the information available and decide forthemselves what to throw out, partly because they don'twant to seem uniformed or be caught by surprise bypotentially important information. They are in a betterposition if they can say: "I knew about that data,assessed it based on the following quality assurancecriteria, and decided not to use it for thisapplication." This is especially true for users near theend of long decision processes, such as hazardous sitecleanups, lengthy ecological risk assessments, or complexnatural resource damage assessments.

For some categories, the editors found no information andinserted the phrase "no information found." This doesnot necessarily mean that no information exists; it

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Although the editors of this document have done theirbest in the limited time available to insure accuracy ofquotes or summaries as being "what the original authorsaid," the proposed interagency funding of a biggerproject with more elaborate peer review and qualitycontrol steps never materialized.

The bottom line: The editors hope users find thisdocument useful, but don't expect or depend onperfection herein. Neither the U.S. Government northe National Park Service make any claims that thisdocument is free of mistakes.

The following is one chemical topic entry (one file among118). Before utilizing this entry, the reader isstrongly encouraged to read the README file (in thissubdirectory) for an introduction, an explanation of howto use this document in general, an explanation of how tosearch for power key section headings, an explanation ofthe organization of each entry, an information qualitydiscussion, a discussion of copyright issues, and alisting of other entries (other topics) covered.

See the separate file entitled REFERENC for the identityof numbered references in brackets.

HOW TO CITE THIS DOCUMENT: As mentioned above, forcritical applications it is better to obtain and cite theoriginal publication after first verifying various dataquality assurance concerns. For more routineapplications, this document may be cited as:

Irwin, R.J., M. VanMouwerik, L. Stevens, M.D.Seese , and W. Basham. 1997. EnvironmentalContaminants Encyclopedia. National Park Service,Water Resources Division, Fort Collins, Colorado.Distributed within the Federal Government as anElectronic Document (Projected public availability

on the internet or NTIS: 1998).

Xylene, p- (p-Xylene, para-xylene, CAS number 106-42-3)

NOTE: The majority of the information in this entry is on thep- isomer of xylene. However, "xylene or xylenes" are oftena mixture of ortho-, meta-, and para- isomers. Theinformation on isomers is sometimes difficult to separate andthe information on mixed xylenes or total xylenes is of someinterest in considering p-xylene. Where information on p-xylene is lacking, consult corresponding sections in the moregeneral "Xylenes, Total" entry.

Br ief Introduction:

Br.Class : General Introduction and Classification Information:

Xylenes (mixed isomers) are considered volatile organiccompounds (VOCs) [868,903]. Xylenes are C2 Benzenes, oneclass of alkyl benzenes.

Xylene, a widely used industrial solvent, is a mixture ofortho-, meta-, and para- isomers [366].

Xylene produced from petroleum ... contains approx 20% o-xylene, 44% m-xylene, 20% p-xylene, and 15% ethylbenzene.Xylene from coal tar generally consists of 10-15% ortho-xylene, 45-70% meta-xylene, 23% para-xylene, and 6-10%ethylbenzene [366].

While o-xylene is recognized as a distinct product inchemical analyses, the m- and p- isomers are generallynot separated during most routine analyses. Therefore,results of analyses of xylenes in environmental samplesare usually presented as the concentration of the o-isomer and the total concentration of the combined m- andp- isomers [602].

p-Xylene and m-xylene cannot be separated by distillationbecause their boiling points are too close. [Kirk-OthmerEncyclopedia of Chemical Technology. 3rd ed., Volumes 1-26. New York, NY: John Wiley and Sons, 1978-1984.,p.24(84) 711] [609].

According to the USCG Emergency Response NotificationSystem (1993), p-xylene was one of the top most spillednon-petroleum chemicals in U.S. waters, by volumereleased [635].

Designated as a hazardous substance under section311(b)(2)(A) of the Federal Water Pollution Control Actand further regulated by the Clean Water Act Amendmentsof 1977 and 1978. These regulations apply to dischargesof this substance. [40 CFR 116.4 (7/1/88)] [609].

Br.Haz : General Hazard/Toxicity Summary:

This compound often occurs together with other aromaticcompounds, some possibly more hazardous than thiscompound alone (see entries for Benzene and "PAHs as agroup").

Except for short term hazards from concentrated spills,this compound has been more frequently associated withrisk to humans than with risk to non-human species suchas fish and wildlife. This is partly because only verysmall amounts are taken up by plants, fish, and birds andbecause this volatile compound tends to evaporate intothe atmosphere rather than persisting in surface watersor soils [764]. However, volatiles such as this compoundhave can pose a drinking water hazard when theyaccumulate in ground water.

Humans are exposed to p-xylene primarily from air,particularly in areas with heavy traffic, near fillingstations, near industrial sources such as refineries orwhere p-xylene is used as a solvent. Exposure may alsoarise from drinking contaminated well water such as mightoccur near leaking underground gasoline storage tanks orfrom spills of petroleum products. (SRC) [609].

Information on Xylenes in general:

In animals, large amounts of xylene can causechanges in the liver and harmful effects on thekidneys, heart, lungs, and nervous system [764].

Long term exposures of animals to low doses ofxylene have not been well studied [764].

The Canadian government (1993) concluded thatxylenes are not ordinarily entering the Canadianenvironment in concentrations that might beexpected to cause adverse effects to aquatic biota,terrestrial wildlife, humans, or to depletion ofstratospheric ozone (exceptions might be spills orother direct releases) [602].

Additional human health issues related to xyleneshave been summarized by ATSDR (not all thehighlights from ATSDR have been summarized in thisentry) [764].

Br.Car : Brief Summary of Carcinogenicity/Cancer Information:

This compound often occurs together with other aromaticcompounds, some possibly more carcinogenic than thiscompound alone (see entries for Benzene and "PAHs as a

group").


Additional human health issues related to xyleneshave been summarized by ATSDR (not all thehighlights from ATSDR have been summarized in thisentry) [764].

EPA 1996 IRIS database information [893]:

Evidence for classification as to humancarc inogenic i ty ; weight -of -ev idenceclassification

Classification: D; not classifiable asto human carcinogenicity

BASIS: Orally administered technicalxylene mixtures did not result insignificant increases in incidences intumor responses in rats or mice of bothsexes.

HUMAN CARCINOGENICITY DATA

None.

ANIMAL CARCINOGENICITY DATA

Inadequate.

Xylene (mixed isomers) has not been treated as acarcinogen for model calculation purposes in someEPA risk-based (RBC and PRG) models [868,903], butthis tentative distinction was made for the purposeof choosing a modeling scenario based on current(often inadequate) knowledge rather than for thepurpose of strongly stating that this compound isdefinitely not a carcinogen; the non-carcinogenicbenchmarks are sometimes nearly as low as thecarcinogenic benchmarks (Stan Smucker, personalcommunication, EPA, 1996).

Br.Dev : Brief Summary of Developmental, Reproductive,Endocrine, and Genotoxicity Information:

p-Xylene produced toxic developmental effects in rats,mice and cod fish; toxic reproductive effects in cod; anddisrupted hormonal balance in rats [609].


In limited studies thus far, the individual isomerswere not found to be genotoxic when tested in anumber of short-term tests [366].

Some information on immunological, reproductive,fetotoxic, and developmental effects points towardssome negative effects of xylene, but theinformation is limited and mixed [764]. Xylenedoes not appear to be particularly genotoxic [764].

Br.Fate : Brief Summary of Key Bioconcentration, Fate,Transport, Persistence, Pathway, and Chemical/PhysicalInformation:

Environmental Fate/Exposure Summary [609]:

p-Xylene will enter into the atmosphere primarily fromfugitive emissions and exhaust connected with its use ingasoline. Industrial sources include emissions frompetroleum refining and its use as a solvent and chemicalintermediate. Discharges and spills on land and waterwaysresult from its use in diesel fuel and gasoline and thestorage and transport of petroleum products. Most of thep-xylene is released into the atmosphere where it mayphotochemically degrade by reaction with hydroxylradicals (half-life 1.7-18 hr). The dominant removalprocess in water is volatilization. p-Xylene ismoderately mobile in soil and may leach into groundwaterwhere it is known to persist for several years despitesome evidence that it biodegrades in both soil andgroundwater. Bioconcentration is not expected to besignificant. The primary source of exposure is from air,especially in areas with high traffic. (SRC)


Like benzene and toluene, xylenes are fairly volatile,and significant xylenes tend to quickly evaporate ifexposed to the atmosphere [764]. However, xylenes can bemore persistent when in groundwater, sediment, or soilmedia not directly exposed to atmosphere. Xylenes tendto migrate to groundwater, and persistence is an issue ingroundwater, where in some cases, they may persist formonths or years [764].

Most xylene in surface water evaporates into the air inless than a day. The rest of it biodegrades slowly intoother chemicals. Only very small amounts are taken up byplants, fish, and birds. We do not know exactly how longxylene stays in water, but we do know that it stayslonger in groundwater than in lakes and rivers, probablybecause it can evaporate from the latter [764].

Xylene evaporates from soil surfaces. Xylene below thesoil surface stays there for several days and may traveldown through the soil and enter groundwater. In the soiland groundwater it may be slowly biodegraded into lessharmful compounds. It is not clearly known how longxylene trapped deep underground in soil or groundwaterpersists, but it may be months or years. Xylene stayslonger in wet soil than in dry soil [764].

Xylenes are bioconcentrated in aquatic organisms to alimited extent. Although more information onbioconcentration would be helpful, the phenomenon ofbiomagnification is not expected to be important forxylene [764].

Synonyms/Substance Identification:

1,4-Dimethylbenzene [609] 1,4-Xylene [609] Benzene, 1,4-dimethyl- [609] p-Dimethylbenzene [609] p-Methyltoluene [609] Scintillar [609] p-XYLOL [609] AI3-52255 [609]

Molecular Formula: C8-H10 [609]

Associated Chemicals or Topics (Includes Transformation Products):

See also the individual entries:

Xylenes, TotalXylene, m-Xylene, o-BTEXEthylbenzene

Metabolism/Metabolites [609]:

Generally, the xylenes are metabolized to corresponding o-, m-, p-toluic acids ... & Excreted in urine free or conjugatedwith glycine as methylhippuric acid. ... A linear relationshipwas found between atmospheric xylene concn & excreted toluicacid. /Xylene/ [Clayton, G. D. and F. E. Clayton (eds.).Patty's Industrial Hygiene and Toxicology: Volume 2A, 2B, 2C:Toxicology. 3rd ed. New York: John Wiley Sons, 1981-1982.3296].

/When admin to rabbit, rat & guinea pig/ p-xylene was excretedas p-toluic acid deriv, but also a 2,5-dimethylphenolglucuronide was isolated ... According to one report, o-, m-,

& p-xylene, in decreasing order, are demethylated to phenol.Generally, the xylenes are metabolized to corresponding o-, m-, p-toluic acids ... & Excreted in urine free or conjugatedwith glycine as methylhippuric acid. [Clayton, G. D. and F.E. Clayton (eds.). Patty's Industrial Hygiene and Toxicology:Volume 2A, 2B, 2C: Toxicology. 3rd ed. New York: John WileySons, 1981-1982. 3298].

Rats given single ip injection of p-xylene suffered 65% lossof pulmonary microsomal p-xylene hydroxylase activity.Pretreatment with phenobarbital incr hepatic p-xylenehydroxylase & cytosolic aldehyde dehydrogenase activities buthad no effect on alc dehydrogenase activity in hepaticcytosol. Experiments in vitro showed that inactivation ofcytochrome p450 by p-xylene required metabolic conversion ofp-xylene to p-tolualdehyde. In as much as lung tissue cannotform p-tolualdehyde (because of low activity of p-methylbenzylalc dehydrogenase), it is assumed that inactivation of lungenzymes in vivo following exposure to p-xylene was due to thealdehyde intermediate which is formed in the liver andtransported to the lung. [PATEL JM ET AL; DRUG METAB DISPOS6 (4): 368-74 (1978)].

In humans ... Exposed to approx 0.2-0.4 Mg/l xylene isomers(o-, m-, p-xylene) or 1:1:1 mixt for up to 8 hr ... Pulmonaryretention was 64%, which was ... Independent of dosage orduration of exposure. After exposure, only 5% of retainedxylenes were elim in expired air. More than 95% ... Excretedby humans into urine in form of methylhippuric acids. ...Small portion ... Excreted into urine as correspondingxylenols. [National Research Council. Drinking Water andHealth. Volume 3. Washington, DC: National Academy Press,1980. 179].

Pseudomonas aeruginosa converts p-xylene into p-methylbenzylalcohol & possibly further to methylbenzoic acid. [Clayton,G. D. and F. E. Clayton (eds.). Patty's Industrial Hygiene andToxicology: Volume 2A, 2B, 2C: Toxicology. 3rd ed. New York:John Wiley Sons, 1981-1982. 3298]

Metab of p-xylene (100 umol) studied in isolated, perfusedrabbit livers and lungs. Release of p-tolualdehyde intocirculation did not occur in perfused rabbit livers. P-toluricacid (n-p-toluylglycine) was major hepatic metabolite, withsmaller amt of toluic acid & p-methylbenzyl alcohol. Rabbitlivers did not produce detectable amt of p-tolualdehyde, 2,5-dimethylphenol or any glucuronide conjugates. One majorpulmonary metab was p-methylbenzyl alc. Predominance of thismetab reflects deficiency of lung tissue in alc dehydrogenase.Perfused lung also produced 2,5-dimethylphenol a derivativenot produced in the liver. During p-xylene metab in perfusedlungs, derivatives which became covalently bound to lungproteins were formed which suggests that p-xylene metab mightproceed at least partially through reactive intermediate(s)

causing destruction of pulmonary cytochrome p450. Metab wasalso characterized using reconstituted monooxygenase systemscontaining purified rabbit pulmonary lung cytochrome p450 (i)& (II). [SMITH BR ET AL; J PHARMACOL EXP THER 223 (3): 736-42(1982)].

The involvement of sequential side-chain oxidn, sulfation, &glutathione conjugation in formation of mercapturic acids fromxylenes was investigated. The position of methyl groupsattached to the aromatic nucleus affected metabolism. Factorsthat are involved in high yield of mercapturic acids afteradmin of o-xylene as compared to m-xylene & p-xylene inclrelatively low apparent affinity of o-methylbenzyl alcohol forcytosolic alcohol dehydrogenase, the relatively high apparentaffinity of o-methylbenzyl alc for cytosolic sulfotransferase,& the high electrophilic reactivity of the o-methylbenzylsulfate. [VAN DOORN R ET AL; J APPL TOXICOL 1 (4): 236-42(1981)].

Meta & para isomers are ... Extensively oxidized to toluicacids (about 90% of the dose), & these are conjugated mostlywith glycine. Hydroxylation to corresponding xylenols alsooccurs to a small extent. [Parke, D. V. The Biochemistry ofForeign Compounds. Oxford: Pergamon Press, 1968. 218].

Water Data Interpretation, Concentrations and Toxicity (All WaterData Subsections Start with "W."):

W.Low (Water Concentrations Considered Low):

No information found. See entry entitled "Xylenes,Total."

W.Hi gh (Water Concentrations Considered High):

The highest concentrations of xylenes in groundwater inCanada have been recorded near waste disposal sites,including beneath landfill sites (from 0.2 to 191 ug/L m-and p-xylenes combined), near deep injection wellsformerly used for the disposal of liquid industrialwaste, and near an active industrial chemical wastedisposal lagoon (up to 3100 ug/L m- and p-xylenescombined [602].

W.Typ ical (Water Concentrations Considered Typical):

m- And p-xylene concentrations of 50 ug/L were measuredin eight test wells in Ontario, Canada. The xylene wasmost likely a result of natural bituminous deposits[602].

Information from HSDB [609]:

DRINKING WATER: In a survey of 30 Canadian watertreatment facilities, the avg value of p-xylenecombined with ethyl benzene was (1 ppb with amaximum value of 10 ppb and 30% of the suppliespos(1). The raw water for the supplies had a lowermax concn of <1 ppb(1). p-Xylene has beenqualitatively detected in the municipal drinkingwater supplies of Cleveland, OH(2), Philadelphia,PA(3), Washington, DC(4), Tuscaloosa, AL andHouston, TX(5). [(1) Otson R et al; J Assoc OffAnal Chem 65: 1370-4 (1982) (2) Sanjivamurthy VA;Water Res 12: 31-3 (1978) (3) Suffet IH et al; p375-97 in Identification and Analysis of OrganicPollutants in Water. Keith H ed. Ann Arbor, MI: AnnArbor Press (1976) (4) Saunders RA et al; Water Res9: 1143-5 (1975) (5) Bertsch W et al; J Chromatogr112: 701-8 (1975) [609].

DRINKING WATER: In a survey of organics in drinkingwater derived from groundwater sources, p- and o-xylene combined were found in 2.1% of 280 samplesites suppyling <10,000 persons and 1.1% of 186sites supplying >10,000 persons. The max combinedconcn were 0.59 and 0.91 ppb, respectively(1). Themax combined amount of m- and p-xylene in bankfiltered Rhine R water in the Netherlands was 0.1ppb(2). In 6 drinking water wells near a landfill,0.3-2.1 ppb of p-xylene was found(3). Detected inall 14 drinking water studies in the lowland ofGreat Britain, 10 from surface water sources and 4from ground supplies(4). [(1) Westrick JJ; J AmerWater Works Assoc 76: 52-9 (1984) (2) Piet GR,Morra CF; pp 31-42 in Artifical GroundwaterRecharge. Huisman L, Olsthorn TN eds. Pitman Publ(1983) (3) DeWalle FB, Chian ESK; J Amer WaterWorks Assoc 73: 206 -11 (1981) (4) Fielding M etal; Organic Micropollutants in Drinking Water. TR-159. Medmenham, UK Water Res Ctr (1981) [609].

GROUNDWATER: In groundwater under a landfill inNorman, OK - 0.9 ppb(1) and under a rapidinfiltration site in Phoenix, AZ - 0.10-49 ppb(2);under a coal gasification site in Wyoming 15 monthsafter gasification complete - 240-830 ppb(3). In arecovery well from a landfill 7 years after closing- 2.9 ppb p-xylene(4). [(1) Dunlap WJ et al; pp96-110 in Organic Pollutants Contributed toGroundwater by a Landfill. USEPA-600/9-76-004(1976) (2) Tomson MB et al; Water Res 15: 1109-16(1981) (3) Stuermer DH et al; Environ Sci Technol16: 582-7 (1982) (4) DeWalle FB, Chian ESK; J AmerWater Works Assoc 73: 206-11 (1981) [609].

SURFACE WATER: In the raw water supplies for 30

Canadian treatment facilities, 23% contained acombination of p-xylene and ethyl benzene whichaveraged <1 ppb and whose max value was <1 ppb insummer and 2 ppb in winter(1). Detected, notquantified in the Black Warrior River inTuscaloosa, AL(2) and the Glatt River inSwitzerland(3). [(1) Otson R et al; J Assoc OffAnal Chem 65: 1370-4 (1982) (2) Bertsch W et al; JChromatogr 112: 701-8 (1975) (3) Zuercher F, GigerW; Vom Wasser 47: 37-55 (1976) [609].

SEAWATER: In Vineland Sound, MA, samples taken over15 months ranged from 4.5-66 parts per trillion forthe p- and m-xylene combined(1). In open andcoastal sections of the Gulf of Mexico, 2.7-24.4parts per trillion for the p- and m-isomers,combined(2). [(1) Gschwend PM et al; Environ SciTechnol 16: 31-8 (1982) (2) Sauer TC Jr et al; MarChem 7: 1-16 (1978) 6. RAIN/SNOW: West LosAngeles, CA, 9 parts per trillion(1). [(1)Kawamura K, Kaplan IR; Environ Sci Technol 17: 497-501 (1983) [609].

W.Concern Levels, Water Quality Criteria, LC50 Values, WaterQuality Standards, Screening Levels, Dose/Response Data, andOther Water Benchmarks:

W.General (General Water Quality Standards, Criteria, andBenchmarks Related to Protection of Aquatic Biota inGeneral; Includes Water Concentrations Versus Mixed orGeneral Aquatic Biota):

The Netherlands' Maximum Permissable Concentration(MPC) for p-xylene for the protection of allspecies in an aquatic ecosystem is 400 ug/L [655].

The Netherlands' Negligible Concentration (NC) forp-xylene is 1% of the MPC, or 4.0 ug/L [655].

NOTE: Above values are based onecotoxicological data.

The Netherlands' Harmonized (between media) MaximumPermissible Concentration (MPC) for either 0-xylene, m-xylene, or p-xylene in water is 380 ug/L[655].

Note: Harmonization takes into account whetheror not the MPC in one media (such as soil)would lead to exceeding the MPC in anothermedia (such as air, water, or sediment) [655].

The Netherlands' Harmonized (between media)

Negligible Concentration (NC) for either o-xylene,m-xylene, or p-xylene in water is 1% of the MPC, or3.8 ug/L [655].

W.Pl ants (Water Concentrations vs. Plants):


W.Inv ertebrates (Water Concentrations vs. Invertebrates):

The most sensitive freshwater organism was thewater flea (Daphnia magna) with a 24-hour LC50 of3.6 mg/L for p-xylene. Among marine organisms, themost sensitive species was the bay shrimp (Cragofranciscorum) with a 96-hour LC50 of 1.7 mg/L forp-xylene [602].

LC100 Tetrahymena pyriformis (ciliate) 3.77mmole/l/24 hr /Conditions of bioassay notspecified/ [Verschueren, K. Handbook ofEnvironmental Data of Organic Chemicals. 2nd ed.New York, NY: Van Nostrand Reinhold Co., 1983.1194] [609].

LC50 Crangon franciscorum (shrimp) 2.0 ppm/96 hr/Conditions of bioassay not specified/[Verschueren, K. Handbook of Environmental Data ofOrganic Chemicals. 2nd ed. New York, NY: VanNostrand Reinhold Co., 1983. 1194] [609].

W.Fi sh (Water Concentrations vs. Fish):

The most sensitive freshwater fish was the rainbowtrout (Oncorhynchus mykiss) with a 96-hour LC50 of2.6 mg/L for the p- isomer. The most sensitivemarine species tested was the young of the stripedbass (Morone saxatilis) with a 96-hour LC50 of 1.7mg/L for the p- isomers [602].


LC50 Poecilia reticulata (guppy) 35 ppm/7 day/Conditions of bioassay not specified/[Verschueren, K. Handbook of Environmental Data ofOrganic Chemicals. 2nd ed. New York, NY: VanNostrand Reinhold Co., 1983. 1194].

TLm Bluegill fresh water 22 ppm/96 hr /Conditionsof bioassay not specified/ [U.S. Coast Guard,Department of Transportation. CHRIS - HazardousChemical Data. Manual Two. Washington, DC: U.S.Government Printing Office, Oct., 1978. ].

LC50 Morone saxatilis (bass) 2.0 ppm/96 hr/Conditions of bioassay not specified/[Verschueren, K. Handbook of Environmental Data ofOrganic Chemicals. 2nd ed. New York, NY: VanNostrand Reinhold Co., 1983. 1194].

LD50 Goldfish 18 mg/l/24 hr /Modified ASTM D 1345method/ [Verschueren, K. Handbook of EnvironmentalData of Organic Chemicals. 2nd ed. New York, NY:Van Nostrand Reinhold Co., 1983. 1194].

TLm Fathead minnow 27-29 mg/l/24-96 hr. /Conditionsof bioassay not specified/ [Verschueren, K.Handbook of Environmental Data of OrganicChemicals. 2nd ed. New York, NY: Van NostrandReinhold Co., 1983. 1194].

Cod eggs were exposed to seawater solutions ofxylenes. Treatment during fertilization with m-xylene or p-xylene induced significant decr infertilization rate at concentrations greater than10 ppm. Fertilized eggs were exposed 3 hr or 6 hrbefore 1st cleavage. Effects upon the earlycleavage pattern were significant from a concninterval of 2-7 ppm. Characteristic effects inclinhibition of formation of cleavage furrow. Smallcells or total absence of cleavage occurred inhighest concentrations (16-35 ppm), while at 8-15ppm, incomplete or uneven cleavage was usual.Exposure to lower concentrations could give a verywrinkled cleavage membrane. [KJOERSVIK E ET AL;SARSIA 67 (4) : 299-308 (1982) [609].

W.Wild life (Water Concentrations vs. Wildlife or DomesticAnimals):


W.Human (Drinking Water and Other Human Concern Levels):

California's Action Limit for p-xylene in drinkingwater is 0.620 mg/L [859].

EPA Region 9 Preliminary remediation goal (PRG) forTap Water, 1995 [868]: No information given.

EPA Region 3 risk based concentration (RBC) valuefor drinking water: 520 ug/L [903].

W.Misc. (Other Non-concentration Water Information):

No information found. See entry entitled "Xylenes,

Total."

Sediment Data Interpretation, Concentrations and Toxicity (AllSediment Data Subsections Start with "Sed."):

Sed.Lo w (Sediment Concentrations Considered Low):


Sed.Hi gh (Sediment Concentrations Considered High):


Sed.Typ ical (Sediment Concentrations Considered Typical):

In unspecified sediment 100 ppb(1). [(1) Storet DataBase [609].

Sed.Con cern Levels, Sediment Quality Criteria, LC50 Values,Sediment Quality Standards, Screening Levels, Dose/ResponseData and Other Sediment Benchmarks:

Sed.Gen eral (General Sediment Quality Standards,Criteria, and Benchmarks Related to Protection of AquaticBiota in General; Includes Sediment Concentrations VersusMixed or General Aquatic Biota):

Based on equilibrium partitioning, the Netherlands'Maximum Permissable Concentration (MPC) for p-xylene for the protection of all sediment-dwellingorganisms is 11 mg/kg dry weight [655].

Based on equilibrium partitioning, the Netherlands'Negligible Concentration (NC) for p-xylene is 1% ofthe MPC, or 0.11 mg/kg dry weight [655].

The above values based on ecotoxicityconsiderations.

The Netherlands' Harmonized (between media) MaximumPermissible Concentration (MPC) for either o-xylene, m-xylene, or p-xylene in sediments is 14mg/kg [655].


The Netherlands' Harmonized (between media)Negligible Concentration (NC) for either o-xylene,

m-xylene, or p-xylene in sediments is 1% of theMPC, or 0.14 mg/kg [655].

Sed.Pl ants (Sediment Concentrations vs. Plants):


Sed.Inv ertebrates (Sediment Concentrations vs.Invertebrates):


Sed.Fi sh (Sediment Concentrations vs. Fish):


Sed.Wild life (Sediment Concentrations vs. Wildlife orDomestic Animals):


Sed.Human (Sediment Concentrations vs. Human):


Sed.Misc. (Other Non-concentration Sediment Information):


Soil Data Interpretation, Concentrations and Toxicity (All SoilData Subsections Start with "Soil."):

Soil.Lo w (Soil Concentrations Considered Low):


Soil.Hi gh (Soil Concentrations Considered High):


Soil.Typ ical (Soil Concentrations Considered Typical):


Soil.Con cern Levels, Soil Quality Criteria, LC50 Values, SoilQuality Standards, Screening Levels, Dose/Response Data andOther Soil Benchmarks:

Soil.Gen eral (General Soil Quality Standards, Criteria,and Benchmarks Related to Protection of Soil-dwellingBiota in General; Includes Soil Concentrations VersusMixed or General Soil-dwelling Biota):

Based on equilibrium partitioning, the Netherlands'Maximum Permissable Concentration (MPC) for p-xylene for the protection of all soil-dwellingorganisms is 11 mg/kg dry weight [655].

Based on equilibrium partitioning, the Netherlands'Negligible Concentration (NC) for p-xylene is 1% ofthe MPC, or 0.11 mg/kg dry weight [655].

The Netherlands' Harmonized (between media) MaximumPermissible Concentration (MPC) for either o-xylene, m-xylene, or p-xylene in soil is 14 mg/kg[655].


The Netherlands' Harmonized (between media)Negligible Concentration (NC) for either 0-xylene,m-xylene, or p-xylene in soil is 1% of the MPC, or0.14 mg/kg [655].

Soil.Pl ants (Soil Concentrations vs. Plants):


Soil.Inv ertebrates (Soil Concentrations vs.Invertebrates):


Soil.Wild life (Soil Concentrations vs. Wildlife orDomestic Animals):


Soil.Hum an (Soil Concentrations vs. Human):

EPA 1996 National Generic Soil Screening Level

(SSL) designed to be conservative and protective atthe majority of sites in the U.S. but notnecessarily protective of all known human exposurepathways, land uses, or ecological threats [952]:

SSL = 1.6E+05 mg/kg for ingestion pathway[952].

SSL = 460 mg/kg for inhalation pathway [952].

SSL = 10 to 200 mg/kg for protection frommigration to groundwater at 1 to 20 Dilution-Attenuation Factor (DAF) [952].

EPA 1995 Region 9 Preliminary remediation goals(PRGs), 1995 [868]:

Residential Soil: 9.9E+02 mg/kg wet wt.Industrial Soil: 9.9E+02 mg/kg wet wt.

NOTE:1) PRGs focus on the human exposure pathwaysof ingestion, inhalation of particulates andvolatiles, and dermal absorption. Values donot consider impact to groundwater orecological receptors.2) Values are based on a non-carcinogenichazard quotient of one.3) PRGs for residential and industriallanduses are slightly lower concentrationsthan EPA Region III RBCs, which consider feweraspects [903].

EPA 1995 Region 3 Risk based concentration (RBC) toprotect from transfers to groundwater:

220 mg/Kg dry weight [903].

Soil.Misc. (Other Non-concentration Soil Information):


Tis sue and Food Concentrations (All Tissue Data InterpretationSubsections Start with "Tis."):

Tis.Pl ants:

A) As Food: Concentrations or Doses of Concern to LivingThings Which Eat Plants:

No information found. See entry entitled "Xylenes,

Total."

B) Body Burden Residues in Plants: Typical, Elevated, orof Concern Related to the Well-being of the OrganismItself:


Tis.Inv ertebrates:

A) As Food: Concentrations or Doses of Concern to LivingThings Which Eat Invertebrates:


B) Concentrations or Doses of Concern in Food ItemsEaten by Invertebrates:


C) Body Burden Residues in Invertebrates: Typical,Elevated, or of Concern Related to the Well-being of theOrganism Itself:


Tis.Fish :

A) As Food: Concentrations or Doses of Concern to LivingThings Which Eat Fish (Includes FDA Action Levels forFish and Similar Benchmark Levels From Other Countries):


B) Concentrations or Doses of Concern in Food ItemsEaten by Fish:

No information in IRIS 1996 (EPA Database) [893] orin PRGs [868] or RBCs [903].

C) Body Burden Residues in Fish: Typical, Elevated, or ofConcern Related to the Well-being of the Organism Itself:

Xylene has been detected in distillates of rainbowtrout and in carp tissue samples from three riversnot known to be contaminated. The estimated tissueconcentrations of m- and p-xylene (combined) inrainbow trout and carp were 0.05 and 0.12 mg/kg

(ppm), respectively [764].

Tis.Wild life: Terrestrial and Aquatic Wildlife, DomesticAnimals and all Birds Whether Aquatic or not:

A) As Food: Concentrations or Doses of Concern to LivingThings Which Eat Wildlife, Domestic Animals, or Birds:


B) Concentrations or Doses of Concern in Food ItemsEaten by Wildlife, Birds, or Domestic Animals (IncludesLD50 Values Which do not Fit Well into Other Categories,Includes Oral Doses Administered in LaboratoryExperiments):


C) Body Burden Residues in Wildlife, Birds, or DomesticAnimals: Typical, Elevated, or of Concern Related to theWell-being of the Organism Itself:

Following exposure of rabbits to atmosphere ofabout 3,000 mg/cu m for 8 hr/day, 6 days/wk, for130 days, xylene was found at slightly higher avgconcentrations in the adrenal (148 ppm), bonemarrow (130 ppm), spleen (115 ppm), & brain (100ppm) than in blood (91 ppm) or in other organs./Xylenes/ [Hayes, Wayland J., Jr. PesticidesStudied in Man. Baltimore/London: Williams andWilkins, 1982. 123] [609].

Tis.Hum an:

A) Typical Concentrations in Human Food Survey Items:


B) Concentrations or Doses of Concern in Food ItemsEaten by Humans (Includes Allowable Tolerances in HumanFood, FDA, State and Standards of Other Countries):


C) Body Burden Residues in Humans: Typical, Elevated, orof Concern Related to the Well-being of Humans:


Tis.Misc. (Other Tissue Information):


Bio.Detail : Detailed Information on Bioconcentration,Biomagnification, or Bioavailability:

Bioconcentration Factors (log BCF) for p-xylene [902]:

1.17 for goldfish,1.68 and 1.17 for fish,2.41 for Selenastrum capricornutum (green alga)

Little bioconcentration is expected, the log BCF = 1.37 foreels(1). Based on the log octanol/water partition coefficient of3.15(2), one estimates the log BCF in fish to be 2.2(3,SRC). [(1)Ogata M, Miyake Y; Water Res 12: 1041-4 (1978) (2) Hansch C, LeoAJ; Medchem project no. 19 Claremont CA: Pomona College (1981) (3)Lyman WJ et al; Handbook of Chemical Property Estimation Methods.New York, NY McGraw Hill p 5-5 (1982)] [609].

Int eractions:


Sixteen men were studied in an exposure chamber to assess theeffect of four hr exposure to toluene (3.25 mmole/cu m), p-xylene (2.84 mmole/cu m) a mixture of toluene and p-xylene(2.20 + 0.94 mmol/cu m) and a control condition. With the aidof microcomputers subjects performed tests of simple reactiontime, short term memory, and choice reaction time immediatelyafter entering the chamber, after two, and after four hours ofexposure. The results indicate that the performance on thetests was unaffected by exposure. In the light of this result,the risk of an acute effect on central nervous functions afterexposure for four hours at these concn was considered to beminimal. [Olson BA et al; Brit J Ind Med 42: 117-22 (1985)].

Eight male subjects were exptl exposed to toluene, p-xylene,and a combination of toluene and p-xylene to study theinfluence of coexposure and exposure to different levels ofeach solvent on their uptake and elimination. The exposureswere performed for 4 hr at exposure levels equiv to or lowerthan the Swedish threshold limit value for toluene, 300 mg/cum (3.2 mmol/cu m). During and after the exposure, solventconcn were measured in blood and in expired air. In addition,the pulmonary ventilation rate was measured during theexposure. Decreases in the blood/end exhaled air concn ratiowere found for both toluene and p-xylene when given incombination compared with separate exposure. The total solventuptake relative to the exposure level was decreased afterexposure to the higher solvent concn, and the apparent

clearance was also decreased after exposure to the higherconcn of solvent. Finally, the blood solvent concn were lowerat the end of the exposure compared with the maximal concnduring each exposure condition. In the kinetics of toluene andp-xylene, the total amt of toluene or p-xylene, or both, seemsto be of major importance. The change in blood/end exhaled airconcn ratio may indicate an effect of coexposure. [Wallen M etal; Br J Ind Med 42 (2): 111-6 (1985)].

In vitro activation expt demonstrated that ... Rabbit hepaticbut not pulmonary microsomal enzyme systems were affected byphenobarbital pretreatment. /In rabbits/ phenobarbital, 3-methylcholanthrene, & chlorpromazine raise lc50 of inhaled p-xylene, but only 3-methylcholanthrene had any effect oninjected solvent. [Clayton, G. D. and F. E. Clayton (eds.).Patty's Industrial Hygiene and Toxicology: Volume 2A, 2B, 2C:Toxicology. 3rd ed. New York: John Wiley Sons, 1981-1982.3298].When consumed prior to exposure, ethanol decreases themetabolic clearance of xylene by approximately one-half./Xylenes/ [Ellenhorn, M.J. and D.G. Barceloux. MedicalToxicology - Diagnosis and Treatment of Human Poisoning. NewYork, NY: Elsevier Science Publishing Co., Inc. 1988. 963

Pretreatment of rats with phenobarbital incr the ld50 of para-xylene more than 20%. [HARPER C ET AL; BIOL REACT INTERMED,(PROC INT CONF) 302-11 (1977)

Humans exposed to 46 or 92 ppm of o-, m-, p-xylene or amixture (1:1:1) of the three for 8 hr absorbed approx 64% ofthe inhaled xylene. No difference in the absorption rate wasreported due to level of exposure, length of exposure, or thetype and/or mixture of the xylene isomers. The absorption ofxylene appeared to vary among individuals due to differencesin ventilation rate. ... Individuals with an incr ventilationrate retained less xylene. [NCI; Monograph on Human Exposureto Chemicals in the Workplace: Xylene p.4-2 (July/1985)].

Male Wister rats exposed to xylene in air (80% m-xylene, 12%p-xylene) for 6 hr/day, 5 days/week for 2 weeks accumulated64.8 mg/xylene/g of perirenal fat after five exposures and127.0 mg/xylene/g of perirenal fat after 10 exposures toxylene. [NCI; Monograph on Human Exposure to Chemicals in theWorkplace: Xylene p.4-4 (July/1985)

Uses/Sources:

Major Uses [609]:

Synthesis of terephthalic acid for polyester resins and fibers("Dacron," "Mylar," "Terylene"); pharmaceutical synthesis;insecticides [Sax, N.I. and R.J. Lewis, Sr. (eds.). Hawley'sCondensed Chemical Dictionary. 11th ed. New York: Van Nostrand

Reinhold Co., 1987. 1243].

Chem intermed for dimethyl terephthalate & terephthalic acid[SRI].

Chem intermed for dimethyl tetrachloroterephthalate-herbicide[SRI].

SOLVENT [SRI].

p-Xylene ... frequently ... used for paints or in the printingtrade. [Wallen M et al; Brit J Indust Med 42: 111-6 (1985)].

Natural Occurring Sources [609]:

Petroleum(1). [(1) NAS; The Alkyl Benzenes page I-1 to I-99(1980)].

Artificial Sources [609]:

Present in exhaust of gasoline engines at 1.9 vol% of emittedHC /m- and p-xylenes/; exhaust of diesel engines at 1.9%emitted HC /m- and p-xylene/; reciprocating gasoline engine at1.3% of emitted HC; rotary gasoline engine at 5.6% of emittedHC /m- and p-xylene/ [Verschueren, K. Handbook ofEnvironmental Data of Organic Chemicals. 2nd ed. New York, NY:Van Nostrand Reinhold Co., 1983. 119].

Emissions from petroleum refining, gasoline and diesel engines(1); evaporative losses during the transport and storage ofgasoline and carburetor losses(1,2). Emissions from its use asa chemical intermediate in the production of dimethylterephthalate and terephthalic acid for polyesterproduction(3). Evaporative losses from its use as asolvent(1,2). [(1) NAS; The Alkyl Benzenes page I-1 to I-99(1980) (2) Graedel TE; Chemical Compounds in the Atmosphere.New York Academic Press p 109 (1978) (3) Chemical MarketingReporter Aug 22 (1983)].

Composite gasoline samples from Los Angeles m- and p-xylenecombined are 6.73 wt%(1). [(1) NAS; The Alkyl Benzenes page I-1 to I-99 (1980)].

Forms/Preparations/Formulations:

Research, 99.99%; Pure, 99.8%; Technical, 99.0%. [U.S. CoastGuard, Department of Transportation. CHRIS - Hazardous ChemicalData. Volume II. Washington, D.C.: U.S. Government Printing Office,1984-5.] [609].

Chem.Detail : Detailed Information on Chemical/Physical Properties:

Solubilities:

78 to 223 mg/L at 25 degrees C (most values 180 to 200) [902].

Sol in alcohol, ether, acetone, benzene [Weast, R.C. (ed.)Handbook of Chemistry and Physics, 68th ed. Boca Raton,Florida: CRC Press Inc., 1987-1988.,p. C-550] [609].

Vapor Pressure:

1160 to 1206 Pa at 25 degrees C (most values near 1170) [902].

138.3 deg C @ 760 mm Hg [Weast, R.C. (ed.) Handbook ofChemistry and Physics, 68th ed. Boca Raton, Florida: CRC PressInc., 1987-1988.,p. D-204] [609].

Henry's Law Constant:

506 to 1185 Pa m(3)/mol (most values 710 to 778) [902].

Octanol/Water Partition Coefficient, log Kow:

2.85 to 3.50 (most values near 3.15) [902].

log Kow = 3.15 (est) [Hansch, C., A. Leo. SubstituentConstants for Correlation Analysis in Chemistry and Biology.New York, NY: John Wiley and Sons, 1979. 232] [609].

Sorption Partition Coefficient, log Koc:

2.05 to 3.08 (most values near 2.52) [902].

Molecular Weight:

106.17 [Weast, R.C. (ed.) Handbook of Chemistry and Physics,68th ed. Boca Raton, Florida: CRC Press Inc., 1987-1988.,p. C-550] [609].

Density/Specific Gravity:

0.86104 @ 20 deg C/4 deg C [The Merck Index. 10th ed. Rahway,New Jersey: Merck Co., Inc., 1983. 1448] [609].

Boiling Point:

138.37 deg C [Kirk-Othmer Encyclopedia of Chemical Technology.3rd ed., Volumes 1-26. New York, NY: John Wiley and Sons,1978-1984.,p. 24(84) 710] [609].

Melting Point:

13.3 deg C [Flick, E.W. Industrial Solvents Handbook. 3rd ed.Park Ridge, NJ: Noyes Publications, 1985. 6418] [609].

Color/Form:

Colorless plates or prisms at low temp [The Merck Index. 10thed. Rahway, New Jersey: Merck Co., Inc., 1983. 1448] [609].

Colorless liquid [Sax, N.I. and R.J. Lewis, Sr. (eds.).Hawley's Condensed Chemical Dictionary. 11th ed. New York: VanNostrand Reinhold Co., 1987. 1243] [609].

Color: Saybolt units +30 (research, pure & technical grades)[Flick, E.W. Industrial Solvents Handbook. 3rd ed. Park Ridge,NJ: Noyes Publications, 1985. 49] [609].

Odor:

Sweet [U.S. Coast Guard, Department of Transportation. CHRIS -Hazardous Chemical Data. Volume II. Washington, D.C.: U.S.Government Printing Office, 1984-5] [609].

Fate.Detail : Detailed Information on Fate, Transport, Persistence,and/or Pathways:

Half-lives of p-xylene in surface water [902]: 168-672 hours,based on estimated aqueous aerobic biodegradation half-life.

Half-lives of p-xylene in groundwater [902]: 336-8640 hours,based on estimated aqueous aerobic and anaerobic biodegradationhalf-lives; estimated half-life from observed persistence ingroundwater of the Netherlands, 0.3 years; abiotic hydrolysis ordehydrohalogenation half-life of 1150 months.

Half-lives of p-xylene in soil [902]: 168-672 hours based onestimated aqueous aerobic biodegradation half-life; disappearancehalf-life from test soils, 2.2 days.

Xylenes can be degraded by micro-organisms in the water.Half-lives for biodegradation by unacclimated organisms in waterhave been estimated to be between 7 and 28 days for each of thethree isomers in aerobic systems, and between 28 and 112 days form- and p-isomers in anaerobic systems [602].

Environmental Fate [609]:

TERRESTRIAL FATE: When spilled on land, p-xylene willvolatilize and leach into the ground. p-Xylene may be degradedduring its passage through soil. The extent of the degradationwill depend on its concentration, residence time in the soil,the nature of the soil, and whether resident microbialpopulations have been acclimated. (SRC)

AQUATIC FATE: In surface waters, volatilization appears to bethe dominant removal process (half-life 1-5.5 days(1,SRC)).Some adsorption to sediment will occur. Although p-xylene isbiodegradable and has been observed to degrade in seawater,there is insufficient data to access the rate of this processin surface waters. Although it has been observed to degrade ingroundwater in one study, it is known to persist for manyyears in groundwater, at least at sites where the

concentration might have been quite high(SRC). [(1) Lyman WJet al; Handbook of Chemical Estimation Methods. McGraw-Hill,NY p 15-1 to 15-34 (1982)].

ATMOSPHERIC FATE: When released into the atmosphere, p-xylenemay degrade by reaction with photochemically produced hydroxylradicals (half-life 1.7 hr in summer and 18 hr in winter(1)).However, ambient levels are detected because of large emission(SRC). [(1) Ravishankara AR et al; Int J Chem Kinetics 10:783-804 (1978)].

Biodegradation [609]:

p-Xylene is degraded in standard biodegradability tests usinga variety of inoculums including sewage, activated sludge andseawater(1-4). It was completely degraded within 8 days ingroundwater in a gas-oil mixture; the acclimation period was3-4 days(5). [(1) Bridie AL et al; Water Res 13: 627-30 (1979)(2) Kitano M; Biodegradation and Bioaccumulation Test onChemical Substances, OECD Tokyo Mtg TSU-No. 3 (1978) (3)Malaney GW, McKinney RE; Water Sewage Works 113: 302-9 (1966)(4) VanderLinden AC; Dev Biodeg Hydrocarbons 1: 165-200 (1978)(5) Kappeler T, Wuhrmann K; Water Res 12: 327-33 (1978) ].

Abiotic Degradation [609]:

p-Xylene reacts with hydroxyl radicals in the troposphere(1-3)with a half-life ranging from 1.7 hr in summer to 18 hr inwinter(1) or a typical loss of 67%/day(3). It is moderatelyreactive under photochemical smog conditions with reportedloss rates varying from 4-25% per hr(4-9), rates typical ofits reaction with hydroxyl radicals(9). Xylenes are resistantto hydrolysis based upon the lack of hydrolyzable function.(SRC) [(1) Ravishankara AR et al; Int J Chem Kinetics 10: 783-804 (1978) (2) Hansen DA et al; J Phys Chem 79: 1763-6 (1975)(3) Singh HB et al; Atmos Environ 15: 601-12 (1981) (4)Yanagihara S et al; 4th Int Clean Air Conf: Photochemicalreactivities of hydrocarbons p 472-7 (1977) (5) Dilling WL etal; Environ Sci Technol 10: 351-6 (1976) (6) Washida N et al;Bull Chem Soc Japan 51: 2215-21 (1978) (7) Kopczynski SL etal; Environ Sci Technol 6: 342 (1972) (8) Altshuller AP et al;Environ Sci Technol 4: 503-6 (1970) (9) Doyle GJ et al;Environ Sci Technol 9: 237-41 (1975) (10) VanAalst RM et al;Comm Eur Comm Symp Phys Chem Behav Atmos Poll EUR6621 1: 136-49 (1980].

Soil Adsorption/Mobility [609]:

No measured values for Koc of p-xylene could be found in theliterature. However, low to moderate adsorption would beexpected based on the log Kow value of 3.15(4). The measuredpermeability for fire clay is 1x10-9 cm/sec and a factor of 4and 50 times faster in ranger shale and kaolinerespectively(1). It has been detected in groundwater under a

rapid infiltration site(2) and passed through soil at a dune-infiltration site on the Rhine River unchanged inconcentration(3). [(1) Green WJ et al; J Water Pollut ControlFed 53: 1347-54 (1981) (2) Tomson MB et al; Wat Res 15:1109-16(1981) (3) Piet GJ et al; in Quality of Groundwater. Int SympProc Van Duijvenbooden W et al eds; Studies Environ Sci 17:557-64 (1981) (4) Hansch C, Leo JJ; Medchem project no. 19Claremont CA: Pomona College (1981) ].

Volatilization from Water/Soil [609]:

Using the Henry's Law constant = 0.314(1), the half-life forevaporation of p-xylene from water with a wind speed of 3m/sec, a current of 1 m/sec, and a depth of 1 m is calculatedto be 3.1 hr(2, SRC). An experiment which measured the rate ofevaporation of m- and p-xylene from a 1:1000 jet fuel:watermixture found that it averaged 0.64 times the oxygenreaeration rate(3). Combining this ratio with the oxygenreaeration rates of typical bodies of water(2), one estimatesthat the half-life for evaporation from a typical river orpond is 27 and 135 hr, respectively(SRC). [(1) NAS; The AlkylBenzenes II-1 to II-51 (1980) (2) Lyman WJ et al; Handbook ofChemical Estimation Methods. New York, NY McGraw Hill p 15-1to 15-34 (1982) (3) Smith JH, Harper JC; 12th Conf on EnvironToxicol: Behavior of hydrocarbon fuels in the aquaticenvionment p 336-53 (1980)].

Absorption, Distribution and Excretion [609]:

For exposure to xylene at concn averaging 100 ppm, the meanmethyl hippuric acid concn should average 1.5 to 2 g/gcreatinine (range 1.0-3.0) in a sample collected during thesecond part of the exposure period. Almost total urinaryexcretion of xylene occurs by 24 hours. The rapid xyleneclearance from blood (plasma half-life of 4 hours) preventsadequate biological monitoring of serum samples. /Xylenes/[Ellenhorn, M.J. and D.G. Barceloux. Medical Toxicology -Diagnosis and Treatment of Human Poisoning. New York, NY:Elsevier Science Publishing Co., Inc. 1988. 963].

Xylenes have been reported to cross the human placenta./XYLENES/ [National Research Council. Drinking Water andHealth. Volume 3. Washington, DC: National Academy Press,1980. 180].

Xylene, when ingested, is readily absorbed by the humansystem, as has been shown in accidental ingestions. Absorptionthrough intact & broken skin occurs readily. ... Xylene isabsorbed mainly through mucous membranes & pulmonary system.... Absorbed xylene is translocated through the vascularsystem. ... /XYLENES/ [Clayton, G. D. and F. E. Clayton(eds.). Patty's Industrial Hygiene and Toxicology: Volume 2A,2B, 2C: Toxicology. 3rd ed. New York: John Wiley Sons, 1981-1982. 3296].

Humans exposed to 46 or 92 ppm of o-, m-, p-xylene or amixture (1:1:1) of the three for 8 hr absorbed approx 64% ofthe inhaled xylene. No difference in the absorption rate wasreported due to level of exposure, length of exposure, or thetype and/or mixture of the xylene isomers. The absorption ofxylene appeared to vary among individuals due to differencesin ventilation rate. ... Individuals with an incr ventilationrate retained less xylene. [NCI; Monograph on Human Exposureto Chemicals in the Workplace: Xylene p.4-2 (July/1985)].

Male Wister rats exposed to xylene in air (80% m-xylene, 12%p-xylene) for 6 hr/day, 5 days/week for 2 weeks accumulated64.8 mg/xylene/g of perirenal fat after five exposures and127.0 mg/xylene/g of perirenal fat after 10 exposures toxylene. [NCI; Monograph on Human Exposure to Chemicals in theWorkplace: Xylene p.4-4 (July/1985)].

Laboratory and/or Field Analyses:

For optimum risk or hazard assessment work, volatile compoundlab methods with very low detection limits [such as EPA Method 8260modified for Selective Ion Mode (SIM) Enhanced Detection Limits]should be used. The investigator should also specify the additionof any relevant compounds (such as related alkyl volatiles)suspected of being present but not typically found on the standardEPA scans. In concert with need to compare values with lowbenchmark concentrations, the regulatory requirements of Statessuch as Wisconsin and the capabilities of better labs, detectionlimits should be as low as possible and in all cases no higher than25 ppb [913] in soil, sediment, or tissue, and if possible nohigher than 1 ppb (better labs can achieve 0.3 ppb) in water.Wisconsin requires a detection limit of 0.5 ug/L for all VOCs[923].

For drinking water, in the past, EPA has recommended thefollowing less rigorous methods for analyses of certain volatiles:Purge and trap capillary gas chromatography (EPA 502.2); gaschromatographic/mass spectrometry (EPA 524.2); purge and trap gaschromatography (EPA 503.1); gas chromatography/mass spectrometry(EPA 524.1); PQL= 0.005 mg/L [893].

Regardless of what lab methods are used, the investigator musttake special precautions to prevent the escape of volatiles duringsample shipment, storage, extraction, and cleanup [798]. Theresults of analyses of volatiles can be dramatically effected bysmall details such as how the samples are collected, stored, held,and analyzed in the lab, since volatile compounds can readilyvolatilize from samples in both field and lab procedures. Therealization that better methods were needed began when the labresults of EPA methods 8020 and 8240 were negative even whencontamination by volatiles was obvious in the field, in otherwords, when investigators began seeing clearly false negativeresults [798]. The use of brass liners for collection resulted in19 fold higher VOCs than when 40 mL vials were used [798]. Afterresearching various papers which documented volatile losses of 9 to

99% during sampling and then finding 100% losses in samples heldover 14 days in their own facilities, the Wisconsin DNR requiresthe following for soil sampling of volatiles:

1) methanol preservation be used for all samples [913,923],and

2) samples stored in brass tubes must be preserved in methanolwithin 2 hours and samples stored in EN CORE samplers must bepreserved in 48 hours [913,923].

3) Detection limits should be no higher than 25 ug/Kg (ppb)dry weight for VOCs or petroleum volatiles in soil samples[913].

For additional details on methods for volatiles and xylenes,and, when to choose various methods, and how to prevent loss ofvolatiles in the field and in the lab, see xylenes entry.

Contaminants data from different labs, different states, anddifferent agencies, collected by different people, are often notvery comparable (see also, discussion in the disclaimer section atthe top of this entry, and the more detailed discussions in thexylenes entry).

It should be kept in mind that quality control field and labblanks and duplicates will not help in the data quality assurancegoal as well as intended if one is using a method prone to falsenegatives. Methods may be prone to false negatives due to the useof detection limits that are too high, the loss of contaminantsthrough inappropriate handling, or the use of an inappropriatemethods such as many of the EPA standard scans. This is one reasonfor using the NOAA expanded scan for PAHs [828]; or method 8270[1013] modified for Selective Ion Mode (SIM) detection limits (10ppt for water, 0.3 to 1 ppb for solids) and additional alkyl PAHanalytes in response to oil spills. Alkyl PAHs are more persistentand less volatile than xylenes. Thus, rigorous low-detection-limitscans for alkyl PAHs are less prone to false negatives than many ofthe standard EPA high-detection-limit analyses for xylenes (RoyIrwin, National Park Service, Personal Communication, 1997).

Description of EPA standard methods 8240 and 8260 from EPAEMMI Database on Lab methods [861]:

Note: 8260 is replacing 8240 [1013].

EPA Method 8240 for Volatile Organics [861]:

OSW 8240A S Volatile Organics - Soil, GCMS 73SW-846 GCMS ug/kg EQL Method 8240A"Volatile Organics by Gas Chromatography/MassSpectrometry (GC/MS): Packed Column Technique" Thevolatile compounds are introduced into the gaschromatograph by the purge and trap method or bydirect injection (in limited applications) [861].The components are separated via the gaschromatograph and detected using a mass

spectrometer, which is used to provide bothqualitative and quantitative information [861].The chromatographic conditions, as well as typicalmass spectrometer operating parameters, are given[861]. If the above sample introduction techniquesare not applicable, a portion of the sample isdispersed in methanol to dissolve the volatileorganic constituents [861]. A portion of themethanolic solution is combined with organic-freereagent water in a specially designed purgingchamber [861]. It is then analyzed by purge andtrap GC/MS following the normal water method [861].The purge and trap process - An inert gas isbubbled through the solution at ambienttemperature, and the volatile components areefficiently transferred from the aqueous phase tothe vapor phase [861]. The vapor is swept througha sorbent column where the volatile components aretrapped [861]. After purging is complete, thesorbent column is heated and backflushed with inertgas to desorb the components, which are detectedwith a mass spectrometer [861].

OSW 8240A W Volatile Organics - Water, GCMS 73SW-846 GCMS ug/L EQL Method 8240A"Volatile Organics by Gas Chromatography/MassSpectrometry (GC/MS): Packed Column Technique" Thevolatile compounds are introduced into the gaschromatograph by the purge and trap method or bydirect injection (in limited applications) [861].The components are separated via the gaschromatograph and detected using a massspectrometer, which is used to provide bothqualitative and quantitative information [861].The chromatographic conditions, as well as typicalmass spectrometer operating parameters, are given[861]. If the above sample introduction techniquesare not applicable, a portion of the sample isdispersed in methanol to dissolve the volatileorganic constituents [861]. A portion of themethanolic solution is combined with organic-freereagent water in a specially designed purgingchamber [861]. It is then analyzed by purge andtrap GC/MS following the normal water method [861].The purge and trap process - An inert gas isbubbled through the solution at ambienttemperature, and the volatile components areefficiently transferred from the aqueous phase tothe vapor phase [861]. The vapor is swept througha sorbent column where the volatile components aretrapped [861]. After purging is complete, thesorbent column is heated and backflushed with inertgas to desorb the components, which are detectedwith a mass spectrometer [861].

EPA Method 8260 (for GC/MS Volatile Organics):

EPA description [861]:

OSW 8260 Volatile Organics - CGCMS 58SW-846 CGCMS ug/L MDL Method 8260"Volatile Organic Compounds by GasChromatography/Mass Spectrometry (GC/MS):Capillary Column Technique" The volatilecompounds are introduced into the gaschromatograph by the purge and trap method orby direct injection (in limited applications)[861]. Purged sample components are trappedin a tube containing suitable sorbentmaterials [861]. When purging is complete,the sorbent tube is heated and backflushedwith helium to desorb trapped samplecomponents [861]. The analytes are desorbeddirectly to a large bore capillary orcryofocussed on a capillary precolumn beforebeing flash evaporated to a narrow borecapillary for analysis [861]. The column istemperature programmed to separate theanalytes which are then detected with a massspectrometer interfaced to the gaschromatograph [861]. Wide capillary columnsrequire a jet separator, whereas narrow borecapillary columns can be directly interfacedto the ion source [861]. If the above sampleintroduction techniques are not applicable, aportion of the sample is dispersed in solventto dissolve the volatile organic constituents[861]. A portion of the solution is combinedwith organic- free reagent water in the purgechamber [861]. It is then analyzed by purgeand trap GC/MS following the normal watermethod [861]. Qualitative identifications areconfirmed by analyzing standards under thesame conditions used for samples and comparingresultant mass spectra and GC retention times[861]. Each identified component isquantified by relating the MS response for anappropriate selected ion produced by thatcompound to the MS response for another ionproduced by an internal standard [861].

Other Misc. (mostly less rigorous) lab methods which havebeen used in the past in media such as drinking water forvolatiles [893] (lab method description from EPA [861]):

EMSLC 502.2 ELCD VOA's - P&T/CGCELCD/CGCPID 44DRINKING_WATER CGCELD ug/L MDL "VolatileOrganic Compounds in Water by Purge and TrapCapillary Column Gas Chromatography with

Photoionization and Electrolytic ConductivityDetectors in Series" This method is used for theidentification and measurement of purgeablevolatile organic compounds in finished drinkingwater, raw source water, or drinking water in anytreatment stage [861]. The method is applicable toa wide range of organic compounds, including thefour trihalomethane disinfection by-products, thathave sufficiently high volatility and low watersolubility to be efficiently removed from watersamples with purge and trap procedures [861]. Aninert gas is bubbled through a 5 mL water sample[861]. The volatile compounds with low watersolubility are purged from the sample and trappedin a tube containing suitable sorbent materials[861]. When purging is complete, the tube isheated and backflushed with helium to desorbtrapped sample components onto a capillary gaschromatography (GC) column [861]. The column istemperature programmed to separate the analyteswhich are then detected with photoionizationdetector (PID) and halogen specific detectors inseries [861]. Analytes are identified by comparingretention times with authentic standards and bycomparing relative responses from the two detectors[861]. A GC/MS may be used for furtherconfirmation [861].

EMSLC 502.2 PID VOA's - P&T/CGCELCD/CGCPID 33DRINKING_WATER CGCPID ug/L MDL "VolatileOrganic Compounds in Water by Purge and TrapCapillary Column Gas Chromatography withPhotoionization and Electrolytic ConductivityDetectors in Series" This method is used for theidentification and measurement of purgeablevolatile organic compounds in finished drinkingwater, raw source water, or drinking water in anytreatment stage [861]. The method is applicable toa wide range of organic compounds, including thefour trihalomethane disinfection by-products, thathave sufficiently high volatility and low watersolubility to be efficiently removed from watersamples with purge and trap procedures [861]. Aninert gas is bubbled through a 5 mL water sample[861]. The volatile compounds with low watersolubility are purged from the sample and trappedin a tube containing suitable sorbent materials[861]. When purging is complete, the tube isheated and backflushed with helium to desorbtrapped sample components onto a capillary gaschromatography (GC) column [861]. The column istemperature programmed to separate the analyteswhich are then detected with photoionizationdetector (PID) and halogen specific detectors in

series [861]. Analytes are identified by comparingretention times with authentic standards and bycomparing relative responses from the two detectors[861]. A GC/MS may be used for furtherconfirmation [861].

EMSLC 503.1 Volatile Aromatics in Water 28DRINKING_WATER GCPID ug/L MDL "VolatileAromatic and Unsaturated Organic Compounds in Waterby Purge and Trap Gas Chromatography" This methodis applicable for the determination of variousvolatile aromatic and unsaturated compounds infinished drinking water, raw source water, ordrinking water in any treatment stage [861].Highly volatile organic compounds with low watersolubility are extracted (purged) from a 5-mlsample by bubbling an inert gas through the aqueoussample [861]. Purged sample components are trappedin a tube containing a suitable sorbent material[861]. When purging is complete, the sorbent tubeis heated and backflushed with an inert gas todesorb trapped sample components onto a gaschromatography (GC) column [861]. The gaschromatograph is temperature programmed to separatethe method analytes which are then detected with aphotoionization detector [861]. A secondchromatographic column is described that can beused to help confirm GC identifications or resolvecoeluting compounds [861]. Confirmation may beperformed by gas chromatography/mass spectrometry(GC/MS) [861].

APHA 6230 D Volatile Halocarbons - CGCELCD STD_METHODS GCELCD "6230 Volatile Halocarbons"GCPID 6230 D [861]. Purge and Trap Capillary-Column Gas Chromatographic Method: This method issimilar to Method 6230 C., except it uses a wide-bore capillary column, and requires a high-temperature photoionization detector in series witheither an electrolytic conductivity ormicrocoulometric detector [861]. This method isequivalent to EPA method 502.2; see EMSLC\502.2[861]. Detection limit data are not presented inthis method, but the method is identical to 502.2;therefore, see EMSLC\502.2 for detection limit data[861]. Method 6230 B., 17th edition, correspondsto Method 514, 16th edition [861]. The othermethods listed do not have a cross-reference in the16th edition [861].

EMSLC 524.1 Purgeable Organics - GCMS 48DRINKING_WATER GCMS ug/L MDL "Measurement ofPurgeable Organic Compounds in Water by PackedColumn Gas Chromatography/Mass Spectrometry" This

is a general purpose method for the identificationand simultaneous measurement of purgeable volatileorganic compounds in finished drinking water, rawsource water, or drinking water in any treatmentstage [861]. Volatile organic compounds andsurrogates with low water solubility are extracted(purged) from the sample matrix by bubbling aninert gas through the aqueous sample [861]. Purgedsample components are trapped in a tube containingsuitable sorbent materials [861]. When purging iscomplete, the trap is backflushed with helium todesorb the trapped sample components into a packedgas chromatography (GC) column interfaced to a massspectrometer (MS) [861]. The column is temperatureprogrammed to separate the method analytes whichare then detected with the MS [861]. Compoundseluting from the GC column are identified bycomparing their measured mass spectra and retentiontimes to reference spectra and retention times in adata base [861]. Reference spectra and retentiontimes for analytes are obtained by the measurementof calibration standards under the same conditionsused for samples [861]. The concentration of eachidentified component is measured by relating the MSresponse of the quantitation ion produced by thatcompound to the MS response of the quantitation ionproduced by a compound that is used as an internalstandard [861]. Surrogate analytes, whoseconcentrations are known in every sample, aremeasured with the same internal standardcalibration procedure [861].

EMSLC 524.2 Purgeable Organics - CGCMS 60DRINKING_WATER CGCMS ug/L MDL "Measurement ofPurgeable Organic Compounds in Water by CapillaryColumn Gas Chromatography/Mass Spectrometry" Thisis a general purpose method for the identificationand simultaneous measurement of purgeable volatileorganic compounds in finished drinking water, rawsource water, or drinking water in any treatmentstage [861]. Volatile organic compounds andsurrogates with low water solubility are extracted(purged) from the sample matrix by bubbling aninert gas through the aqueous sample [861]. Purgedsample components are trapped in a tube containingsuitable sorbent materials [861]. When purging iscomplete, the sorbent tube is heated andbackflushed with helium to desorb the trappedsample components into a capillary gaschromatography (GC) column interfaced to a massspectrometer (MS) [861]. The column is temperatureprogrammed to separate the method analytes whichare then detected with the MS [861]. Compoundseluting from the GC column are identified by

comparing their measured mass spectra and retentiontimes to reference spectra and retention times in adata base [861]. Reference spectra and retentiontimes for analytes are obtained by the measurementof calibration standards under the same conditionsused for samples [861]. The concentration of eachidentified component is measured by relating the MSresponse of the quantitation ion produced by thatcompound to the MS response of the quantitation ionproduced by a compound that is used as an internalstandard [861]. Surrogate analytes, whoseconcentrations are known in every sample, aremeasured with the same internal standardcalibration procedure [861].

Xylenes are a component of BTEX (see also BTEX entry).

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