HETA 98-0017-2699 United States Postal Service … 98-0017-2699 United States Postal Service Omaha,...

HETA 98-0017-2699United States Postal Service

Omaha, Nebraska

Daniel Hewett, CIHGina Buono, MD, MPH

This Health Hazard Evaluation (HHE) report and any recommendations made herein are for the specific facility evaluated and may not be universally applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved. Additional HHE reports are available at http://www.cdc.gov/niosh/hhe/reports



This Health Hazard Evaluation (HHE) report and any recommendations made herein are for the specific facility evaluated and may not be universally applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved.


applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved. Additional HHE reports are available at http://www.cdc.gov/niosh/hhe/reports

http://www.cdc.gov/niosh/hhe/reports



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PREFACEThe Respiratory Disease Hazard Evaluations and Technical Assistance Program (RDHETAP) of the NationalInstitute for Occupational Safety and Health (NIOSH) conducts field investigations of possible health hazardsin the workplace. These investigations are conducted under the authority of Section 20(a)(6) of theOccupational Safety and Health Act of 1970, 29 U.S.C. 669(a)(6) which authorizes the Secretary of Healthand Human Services, following a written request from any employer or authorized representative ofemployees, to determine whether any substance normally found in the place of employment has potentiallytoxic effects in such concentrations as used or found.

The RDHETAP also provides, upon request, technical and consultative assistance to Federal, State, and localagencies; labor; industry; and other groups or individuals to control occupational health hazards and toprevent related trauma and disease. Mention of company names or products does not constitute endorsementby NIOSH.

ACKNOWLEDGMENTS AND AVAILABILITY OF REPORTThis report was prepared by Daniel J. Hewett, CIH, and Gina Buono, MD, MPH, of the Respiratory DiseaseHazard Evaluations and Technical Assistance Program, Division of Respiratory Disease Studies (DRDS).Special assistance in paper dust characterization was provided by Bill Jones, Ph.D., EnvironmentalInvestigations Branch (EIB), DRDS. Field assistance was provided by Patrick Hintz (EIB, DRDS), JeanMead, Pathology and Physiology Research Branch (PPRB), Health Effects Laboratory Division (HELD),and Scott Manetz, (PPRB, HELD). Desktop publishing by Terry Stewart. Review and preparation forprinting was performed by Penny Arthur.

Copies of this report have been sent to employee and management representatives at the US Postal Serviceand the OSHA Regional Office. This report is not copyrighted and may be freely reproduced. Single copiesof this report will be available for a period of three years from the date of this report. To expedite yourrequest, include a self-addressed mailing label along with your written request to:

NIOSH Publications Office4676 Columbia ParkwayCincinnati, Ohio 45226

800-356-4674

After this time, copies may be purchased from the National Technical Information Service (NTIS) at5825 Port Royal Road, Springfield, Virginia 22161. Information regarding the NTIS stock number may beobtained from the NIOSH Publications Office at the Cincinnati address.

For the purpose of informing affected employees, copies of this report shall beposted by the employer in a prominent place accessible to the employees for aperiod of 30 calendar days.

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Health Hazard Evaluation Report 98-0017-2699United States Postal Service

Omaha, NebraskaJuly 1998

Daniel Hewett, CIHGina Buono, MD, MPH

SUMMARYIn October 1997, the National Institute for Occupational Safety and Health (NIOSH) received a health hazardevaluation (HHE) request from the National Postal Mailhandlers Union, AFL-CIO (NPMU) to conduct anHHE at the United States Post Office Mail Processing and Distribution Center, Omaha, Nebraska. A NPMUrepresentative requested an evaluation of worker exposure to paper dust, mold spores, and ink mist/dust inthe first and second floors of the mail processing plant and the basement of a warehouse annex. In therequest, the NPMU listed concerns regarding inhalation and skin exposures resulting in adult-onset asthmacases, recurrent sinus and respiratory infections, allergy treatments for paper dust and mold, lung infections,and recurrent dermatitis.

On December 9 - 12, 1997, NIOSH investigators performed a walkthrough survey of the worksite and metwith NPMU and US Postal Service representatives to discuss health issues related to worker exposure topaper dust, mold spores, and ink dust/mist. Material safety data sheets (MSDSs) of products used in the mailprocessing and warehouse areas were reviewed. Potential organic dust exposures include paper dust, dustsassociated with the operation of heating, ventilating, and air conditioning (HVAC) systems, and dusts createdby mail sack handling in the annex. Investigators performed quantitative area air sampling for fungal sporesin the second floor plant and warehouse areas; aerosols and bulk dusts were collected for microscopy. Bulkdusts from mail sorting machines were collected and analyzed for microbial contaminants. Of approximately897 mailhandlers, clerks, and maintenance personnel, 14 individuals chose to participate in worker interviewswith the NIOSH physician; 11 participated in person, and 3 via telephone. Work histories, health effects,and medical histories were discussed during the interviews.

On January 27, 1998, NIOSH investigators returned to inspect 18 HVAC systems. HVAC maintenanceprocedures were reviewed. Bulk material and water samples from HVAC drain pans were collected andanalyzed for microbial contaminants. Qualitative and quantitative aerosol concentrations and particle sizedistribution data were obtained for general areas of the second floor plant, and during cleaning of mail sorters(delivery point bar code sorters).

A total of 9 airborne spore samples were collected and analyzed for fungal concentration and fungalidentification. A total of 15 bulk dust samples were collected and analyzed for colony counts per gram ofdust and fungal identification. Five particle size selective area samples were collected.

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No exposure limits as enforced by the Occupational Safety and Health Administration (OSHA) orrecommended by NIOSH or the American Conference of Governmental Industrial Hygienists (ACGIH) wereexceeded for paper dust concentrations in air.

In the main plant, no airborne fungi concentrations were significantly elevated compared to outdoors.Airborne concentrations of Aspergillus and Penicillium fungi were significantly elevated in the annex duringmail sack stacking compared to outdoors.

Compared to bulk dusts collected from a return air grate, freshly generated paper dust from mail sorters isnot a significant source of fungi in the plant. Bulk dust from a return air grate on the second floor of theplant contained fungi at concentrations 60 to 100 times higher than that of bulk dusts from mail sorters,which indicates paper dust is a matrix which supports the growth of fungi in close proximity to the airdistribution system.

On the basis of environmental data and information gathered from employee interviews, NIOSHinvestigators did not find clear evidence that employee symptoms were caused by exposure tomicrobial contaminants or paper dust.

Since inks sprayed onto mail pieces were very quick drying, applied inside enclosed areasof sorters, and any volatile fraction was diluted by the relatively large volume of air in theworkspace, exposure to inks was not considered to present a significant health risk toworkers in proximity to machines which spray ink onto mail pieces.

Recommendations are made to control the accumulation of paper dust, improve theoperation and cleaning of HVAC systems, and provide respiratory protection from paper andnon-specific dusts if exposures initiate or aggravate respiratory conditions.Recommendations for respirator selection are presented in this report.

Keywords: SIC 7331 (Mailing service), Paper Dust, Fungi, HVAC, Mail Handling, Mail Processing,Mail Sorting, Bulk Dust, Particle Size, PNOR, PNOC, Ink, Culling.

TABLE OF CONTENTS

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii

Acknowledgments and Availability of Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

Table of Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Environmental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Medical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Evaluation Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Paper Dust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Microbiological Contaminants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Environmental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Airborne Microbial Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Bulk Microbial Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Air Handler Inspections in the Plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Dust Concentrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Particle Size Distributions (Gravimetric) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Aerosol and Bulk Dust Microscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Medical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Community Practitioner Interviews . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Worker Interviews . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Medical Records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Accident and Illness Reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Table 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Figure 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Figure 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Figure 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Appendices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Health Hazard Evaluation Report No. 98-0017-2699 Page 1

INTRODUCTIONIn October 1997, the National Institute forOccupational Safety and Health (NIOSH)received a request from union representativesof the National Postal Mailhandlers Union,AFL-CIO (NPMU) to conduct a health hazardevaluation (HHE) at the United States PostOffice Mail Processing and DistributionCenter, Omaha, Nebraska. The Omaha MailProcessing and Distribution Center (OMPDC)receives, sorts, and prepares mail for delivery.

The request was initiated by reports ofinhalation and skin exposures among 20 to 30workers identified by union representatives ashaving adult-onset asthma, recurrent sinus andrespiratory infections, and allergy withsurgery required to remove infected passagesin the sinus cavity. The request reported thatallergy treatments were required for paperdust, mold, and other infections, and thatworkers also experienced recurrent dermatitis.The requesters associated the health effectswith dust, mold, and inks aerosolized by mailprocessing and maintenance of mailprocessing machines in the main building, andconstruction of cardboard boxes and handlingmail sacks in the warehouse (annex). Someworkers expressed concern for the long-termhealth effects of paper dust inhalation.

In response to this request, NIOSHinvestigators performed a walkthrough surveyon December 9 - 12, 1997. Material safetydata sheets (MSDSs) of products used in themail processing and warehouse areas werereviewed, heating, ventilating, and airconditioning (HVAC) systems wereinspected, and occupational safety and healthprogram records were reviewed. Interviewswere conducted with management, OSHArepresentatives, and workers. NIOSHinvestigators performed quantitative area airsampling for fungal spores in the second floorof the main OMPDC plant and annex areas;

aerosols and bulk dusts were collected formicroscopy. Bulk dusts from sortingmachines and return air grates were collectedand analyzed for microbial contaminants.

On January 27, 1998, NIOSH investigatorsreturned to the OMPDC to perform anenvironmental survey which included aninspection of 18 HVAC systems and a reviewof HVAC maintenance procedures. Bulkmaterial and water samples from HVAC drainpans were collected for analysis of microbialcontaminants. Qualitative and quantitativeaerosol concentrations and particle sizedistribution data were obtained for threegeneral areas of the second floor plant and inareas in proximity to delivery point bar codesorter cleaning.

The purpose of this report is to provideobservations from the two site visits, reportthe results of airborne dust andmicrobiological sampling, and offerconclusions and recommendations based onobservations, worker interviews, andmeasurement results. This is the final reportof this NIOSH safety and health evaluation.

BACKGROUNDThe OMPDC is a two building complex indowntown Omaha, Nebraska. One building isa four story steel frame and concretestructure. The building contains loadingdocks, mail sorting machinery, administrativeoffices, a post office, and conveyors fortransporting packages and trays filled withletters. This building, hereafter referred to asthe “plant,” is where packages and letters arereceived, sorted, and shipped. The first andsecond floors of the plant are the primarywork areas for mail sorting; the second floorcontains automated equipment for high-speedsorting of letters. Packages are manuallyhandled and sorted on the first floor. The

Page 2 Health Hazard Evaluation Report No. 98-0017-2699

second floor sorting machines generate mostof the paper dust in the plant.

The other building is a two-story steel frameand concrete structure, which is leased space.Only the basement of the building is used byp o s t a l w o r ke r s ; i t c o n t a i n s aloading/unloading bay, large open storageareas, and two box-making machines thatcreate cardboard trays for letters or packages.This building, hereafter referred to as the“annex,” is where mail boxes, mail processingcarts, cardboard boxes, and mail sacks arestored and re-distributed. Materials arehandled manually or with a natural gas fueledforklift.

The plant employs approximately 897mailhandlers, clerks, and maintenanceworkers throughout three work shifts. Shiftsare referred to as Tour 1, 10:00 p.m.-6:30 a.m.(358 workers); Tour 2, 6:00 a.m.-2:30 p.m.(218 workers); and Tour 3, 2:00 p.m.-10:30p.m. (351 workers). The annex employs up toeight boxmakers or mailhandlers within thesame tours.

Packages enter the plant culling area wherethey are sent to first floor staging areas ormanual sorting areas. Packages are loadedinto bags and sent to a loading dock. Lettersentering the culling area are sized and sorted;some letters are sent to manual key coderswho route mail manually. After machinesorting or manual coding, letters are sent tothe second floor (Figure 1) optical characterreaders (ISS, OSS, and Mark 2 machines)where routing information is applied in theform of a bar code. Next, letters enter autofacer counter sorters or delivery point barcode sorters where they are set into cardboardtrays according to mail routes. Letter traysare sent to first floor flat sorting machines orrobotic sorters, then to a loading dock forsubsequent delivery.

The second floor contains 5 delivery point barcode sorter 150 stackers, 9 delivery point barcode sorter 190 stackers, 4 auto facer countersorters, and 13 optical character readers in alarge open bay with a 25 foot ceiling. Thefloor also contains breakrooms, restrooms,locker rooms, ceiling-suspended conveyors,and HVAC ducts and diffusers. Mezzaninesabout 15 feet above the plant floor houseseven HVAC systems which ventilate thesecond floor. The HVAC system air handlers(AH) are single-zone, constant volumeheating and cooling-coil equipped units.Outdoor and return air is filtered by roll-typefilters composed of spun synthetic material ofrelatively low efficiency (less than 30%efficiency, dust spot testing method).

Maintenance workers clean readers andsorters to keep paper dust from inhibiting theflow of mail through the machines and cleanpaper dust from optics to preventmalfunctions. Maintenance work isconducted throughout the tours; auto facercounter sorters are typically cleaned on Tour1. However, most maintenance workers (77of 114) work on Tour 2, when lower mailvolume allows greater access to DBCS mailsorters and other sorters/readers for routinecleaning. Sorter and reader cleaning(hereafter referred to as “blowout”)procedures require workers to open machinepanels and vacuum as many interior andexterior surfaces as possible before usingcompressed air (about 30 psi) to blow theremaining paper dust from the machines.Workers performing blowouts are required towear “goggles or face mask” eye protectionwhen using compressed air.

METHODS

EnvironmentalBecause most sorters and readers are on thesecond floor of the plant, this area was


selected for paper dust sampling in proximityto blowout operations. Since many HVACsystem drain pans were covered in dry flakydeposits, and other pans were filled withwater from supplemental humidification bywater spray, the investigators decided toperform bioaerosol and bulk sampling toidentify a potential source of microbialcontamination that could plausibly explaincertain respiratory complaints amongemployees. The second floor plant waschosen for microbiological sampling becauseits airspace is serviced by seven HVACsystems, and the sack storage area of theannex was chosen because workers identifiedthe area as one of concern for aerosolizationof fungi.

The first environmental evaluation took placeon December 9 - 12, 1997, fromapproximately 8:00 a.m. to 8:00 p.m.Samples of the ground, first, second, androoftop AHs were inspected.

Area airborne fungal spore samples werecollected from one outdoor (1st floor loadingdock) and two indoor plant locations (deliverypoint bar code sorter #6 and auto facercounter sorter #2) and one outdoor (alleyway)and two indoor (sack storage) annexlocations. Spores were collected forapproximately 100 minutes with short-cowlopen face cassettes onto 25 millimeter (mm)polyvinyl chloride (PVC) filters attached toair pumps calibrated at 25 liters per minute(lpm). Spores were identified andenumerated.

Duplicate bulk dust samples were collectedfor viable fungi characterization andenumeration. Dusts were collected in sterilepolypropylene tubes. Paper dust sampleswere collected from the interior of deliverypoint bar code sorters #6 and #7. Dust wasalso collected from the return air grate in thefloor of the mezzanine underneath AH S3,and in the annex from the desk in the sack

storage area and from the box maker conveyorbelt. Bulk dust was cultured onto cornmealagar (CMA) and malt extract agar (MEA) forthe enumeration of mesophilic fungi, andDG18 agar for enumeration of xerophilicfungi. Agar plates were incubated at 25 "C.Fungi were identified and enumerated.In order to microscopically characterizeparticulate exposures in the plant and annex,a variety of settled dust and air samples werecollected. For settled dust sampling, twotypes of samples were obtained. On surfaceswhere heavy loading was detected, dust wasscraped directly into collection vials. Onsurfaces with lighter loadings, sticky tapesamplers were used. Samples were collectedfrom delivery point bar code sorters #6 and#7, and from a window sill east of the autofacer counter sorters. These samples wereanalyzed by stereomicroscopy, polarizedlight microscopy, and scanning electronmicroscopy. Air samples for microscopywere collected by drawing air at a flow rate of2.0 liters per minute (L/min) through bothpolycarbonate and cellulose ester filters.These samples were collected with anopen-faced inlet in order to achieve an evendensity of particles across the filter. Sampleswere collected in the plant adjacent to andduring blowout of delivery point bar codesorters #6 and #7 at points 10 and 30 feetfrom the machines. Samples were collectedin the annex at points 10 and 30 feet frommail sack handling and stacking. Thecellulose ester filters were examined by lightmicroscopy. The polycarbonate filters weregold/palladium coated prior to examination byscanning electron microscopy.

The second environmental evaluation tookplace on January 27, 1998, fromapproximately 8:00 a.m. to 6:00 p.m. Areaparticle size distribution samples werecollected using 8-stage Anderson Marple 298impactors with impaction grease coated Mylarsubstrates at a calibrated flow rate of 2.0 lpm.Ambient air samples were collected from


three locations in the second floor plant, andone each during blowout of delivery point barcode sorters #7 and #13. In parallel withparticle size sampling during blowout ofdelivery point bar code sorters #7 and #13,qualitative real-time aerosol concentrationswere characterized with a DUSTRAK™Model 8520 Aerosol Monitor laserphotometer. Nineteen HVAC systems wereinspected and HVAC maintenance procedureswere reviewed. Bulk material and watersamples from HVAC drain pans werecollected and analyzed for microbialcontaminants. Dried material was collectedfrom AHs F5, S6, and S7; two water sampleswere collected from S4. Samples werecultured onto cellulose agar, rose bengal agar,DG18, and MEA.

MedicalConfidential open-ended personal andtelephone interviews were conducted of postalworkers. Interview times were set up at thepost office in a private area. The interviewtimes overlapped various shifts to provideconvenient times for the workers to come foran interview, as well as to minimally disruptthe job. Interviews were also conducted offthe work site for those individuals whoexpressed reluctantance to be interviewed atthe workplace.

NIOSH investigators invited all postalworkers to be interviewed. Workers who hadpreviously identified themselves to the Unionas having work related health complaints werecontacted by the Union and informed of theinterviewer’s availability. Flyers were postedinforming workers of the reason for theNIOSH visit as well as times and locations ofinterviews. Times and locations of theinterviews were also broadcast over theworkers’ network TV “bulletin board.”Workers were allowed to leave their workstations for medical interviews which wereconducted onsite. Interviews were also

conducted off site at the NPMU union hall. Ifa convenient time was not available forworkers, interviews via telephone at theworkers’ convenience were arranged throughthe Union. Open-ended health questions wereasked regarding work related respiratoryproblems. Telephone interviews were alsoconducted with local community practitionersto assess the prevalence of health complaintsof the postal workers, as well as theprevalence of respiratory disease in thecommunity. The practitioners were selectedbecause they had previously rendered care toone of the postal workers. The OMPDCaccident and illness reports were reviewed, aswell as any available medical records.

EVALUATION CRITERIAAs a guide to the evaluation of the hazardsposed by workplace exposures, NIOSH fieldstaff employ environmental evaluation criteriafor the assessment of a number of chemicaland physical agents. These criteria areintended to suggest levels of exposure towhich most workers may be exposed up to 10hours per day, 40 hours per week for aworking lifetime without experiencingadverse health effects. It is, however,important to note that not all workers will beprotected from adverse health effects eventhough their exposures are maintained belowthese levels. A small percentage mayexperience adverse health effects because ofindividual susceptibility, a pre-existingmedical condition, and/or a hypersensitivity(allergy). In addition, some hazardoussubstances may act in combination with otherworkplace exposures, the generalenvironment, or with medications or personalhabits of the worker to produce health effectseven if the occupational exposures arecontrolled at the level set by the criterion.These combined effects are often notconsidered in the evaluation criteria. Also,some substances are absorbed by direct


contact with the skin and mucous membranes,and thus potentially increase the overallexposure. Finally, evaluation criteria maychange over the years as new information onthe toxic effects of an agent becomesavailable.

The primary sources of environmentalevaluation criteria for the workplace are: (1)NIOSH Recommended Exposure Limits(RELs)1, (2) the American Conference ofGovernmental Industrial Hygienists (ACGIH)Threshold Limit Values (TLVs™)2, and (3)the U.S. Department of Labor, OSHAPermissible Exposure Limits (PELs)3.In July 1992, the 11th Circuit Court ofAppeals vacated the 1989 OSHA PEL AirContaminants Standard. OSHA is currentlyenforcing the 1971 standards which are listedas transitional values in the current Code ofFederal Regulations; however, some statesoperating their own OSHA approved jobsafety and health programs continue toenforce the 1989 limits. NIOSH encouragesemployers to follow the 1989 OSHA limits,the NIOSH RELs, the ACGIH TLVs, orwhichever are the more protective criterion.The OSHA PELs reflect the feasibility ofcontrolling exposures in various industrieswhere the agents are used, whereas NIOSHRELs are based primarily on concerns relatingto the prevention of occupational disease. Itshould be noted when reviewing this reportthat employers are legally required to meetthose levels specified by an OSHA standardand that the OSHA PELs included in thisreport reflect the 1971 values.

A time-weighted average (TWA) exposurerefers to the average airborne concentration ofa substance during a normal 8- to 10-hourworkday. Some substances haverecommended short-term exposure limits(STEL) or ceiling values which are intendedto supplement the TWA where there arerecognized toxic effects from higherexposures over the short-term.

Paper DustPaper dust generated by mail processing isobviously a complex and uncontrolledmixture of papers of unknown origin; theaggregate dust generated by mail sorters andaerosolized by maintenance procedures isdifficult to characterize. It is likely thatexposures to chemicals used in themanufacture of paper, in association withpaper dust, would be well below anyapplicable occupational exposure limits forpaper dyes, bleaching agents, and otherchemicals associated with papermanufacturing.

Paper dust exposure has been regulated underthe OSHA “nuisance dust” or particulate nototherwise regulated (PNOR) PEL. In 1986,OSHAs Occupational Health ReviewCommission ruled that paper dust is anorganic dust; therefore the nuisance duststandard did not apply to paper dust.4 In1993, OSHA issued a notice that all inert,nuisance, and organic particulate would becovered under the PNOR standard if no otherexposure limit was applicable. Presently,paper dust exposures are limited under theOSHA PNOR standard (15 micrograms percubic meter [mg/m3] total dust, 5 mg/m3

respirable dust).5,6 The PNOR criteria wereestablished to minimize mechanical irritationof the eyes and nasal passages, and to preventvisual interference. Since wood containsabout 50 to 70% cellulose7, the cellulosecontent of paper could plausibly limit an 8-hour TWA exposure to paper dust by OSHA(15 mg/m3 total dust, 5 mg/m3 respirabledust), NIOSH (10 mg/m3 total dust, 5 mg/m3

respirable dust) or ACGIH (10 mg/m3 totaldust) exposure limits.

Formerly referred to as nuisance dust, theACGIH TLV preferred terminology fornon-specific particulate is particulates nototherwise classified (PNOC)2 The criteria forthe classification of a substance as a PNOC


include the following lung pathology: (1) thearchitecture of the air spaces remains intact;(2) collagen (scar tissue) is not formed to asignificant extent; and 3) the tissue reaction ispotentially reversible.7 The ACGIHrecommended TLV for exposure to a PNOCis 10.0 mg/m3 total dust, 8-hour TWA.NIOSH has not developed specific evaluationcriteria for PNOR/C exposures.

Paper dust can be categorized as an organicdust because it is of vegetable origin. Sometypes of organic dusts have been associatedwith acute responses (irritation or toxicpneumonitis), long-term responses (chronicbronchitis), or hypersensitivity responses.8

MicrobiologicalContaminantsMicroorganisms (including fungi andbacteria) are normal inhabitants of theenvironment. The saprophytic varieties(those utilizing non-living organic matter as afood source) inhabit soil, vegetation, water, orany reservoir that can provide an amplesupply of a nutrient substrate. Under theappropriate conditions (optimum temperatureand pH, and with sufficient moisture andava i l ab l e n u t r i e n t s ) s ap rophyt i cmicroorganism populations can be amplified.Through various mechanisms, theseorganisms can then be disseminated asindividual cells or in association with soil,dust, or water. In the outdoor environment,the levels of microbial aerosols will varyaccording to the geographic location, climaticconditions, and surrounding activity. Indoors,the concentration of certain microorganismsmay vary somewhat as a function of thecleanliness of the HVAC system and thenumbers and activity level of the occupants.With the exception of certain human-shedbacteria, indoor levels are expected to bebelow outdoor levels (depending on HVACsystem filter efficiency) with consistently

similar ranking among the microbialspecies.9,10

Some individuals manifest increasedimmunologic responses to antigenic agentsencountered in the environment. Theseresponses and the subsequent expression ofallergic disease is based, partly, on a geneticpredisposition.11 Allergic diseases typicallyassociated with exposures in indoorenvironments include allergic rhinitis (nasalallergy), allergic asthma, allergicbronchopulmonary aspergillosis (ABPA), andextrinsic allergic alveolitis (hypersensitivitypneumonitis).12 Allergic respiratory diseasesresulting from exposures to microbial agentshave been documented in agricultural,biotechnology, office, and homeenvironments.13,14,15,16,17,18,19,20

Individual symptoms vary according todisease. Allergic rhinitis is characterized byparoxysms of sneezing; itching of the nose,eyes, palate, or pharynx; nasal stuffiness withpartial or total airflow obstruction; andrhinorrhea (runny nose) with postnasaldrainage. Allergic asthma is characterized byepisodic or prolonged wheezing and shortnessof breath in response to bronchial (airways)narrowing. Allergic bronchopulmonaryaspergillosis is characterized by cough,lassitude, low-grade fever, and wheezing.12,21

Heavy exposures to airborne microorganismscan cause an acute form of extrinsic allergicalveolitis which is characterized by chills,fever, malaise, cough, and dyspnea (shortnessof breath) appearing four to eight hours afterexposure. In the chronic form, thought to beinduced by continuous low-level exposure,onset occurs without chills, fever, or malaiseand is characterized by progressive shortnessof breath with weight loss.22

Acceptable levels of airborne microorganismshave not been established, primarily becauseallergic reactions can occur even withrelatively low air concentrations of allergens,


and individuals differ with respect toimmunogenic susceptibilities. The currentstrategy for on-site evaluation ofenvironmental microbial contaminationinvolves an inspection to identify sources(reservoirs) of microbial growth and potentialroutes of dissemination. In those locationswhere contamination is visibly evident orsuspected, bulk samples may be collected toidentify the predominant species. In limitedsituations, air samples may be collected todocument the presence of a suspectedmicrobial contaminant. A significantly higherconcentration of airborne microorganisms(about 10 times or greater) in the area ofinterest compared to outdoor or control areasindicates that growth may have occurred.

RESULTS

Environmental

Airborne Microbial Sampling

Indoor spore counts in the plant areassurrounding delivery point bar code sorter #6and auto facer counter sorter #2 were notconsidered to be significantly elevatedrelative those detected outdoors. Fungiconcentrations in the sack storage area of theannex (6,000 spores per cubic meter of air,Spores/m3) during sack stacking weresignificantly elevated compared to outdoorconcentrations (< 463 Spores/m3); Aspergillusand Penicillium were dominant (75% of totalspores). Bulk Microbial Sampling

Annex bulk dust fungi counts on the conveyorin the box making area averaged 16,200colony forming units per gram (CFU/g);Penicillium was dominant (43% of CFUs).On the sack storage area desk, countsaveraged 92,000 CFU/g; Cladosporium was

dominant (47%) followed by Penicillium(32%).

Concentrations of fungi in paper dust samplesfrom delivery point bar code sorter #7averaged 5700 CFU/g; no species of fungiwere dominant. Concentrations of fungi inpaper dust from delivery point bar code sorter#6 averaged 2900 CFU/g; Penicillium wasdominant (46%). Concentrations of fungi inpaper and other dusts accumulated on thereturn air grate underneath AH S3 averaged323,000 CFU/g; four fungi were predominant-Penicillium (26%), yeasts (20%), Aspergillusspecies (20%), and Cladosporium (13%).

Concentrations of fungi in the dry, flakydeposits in a sample of AH (F5, S6 and S7)drain pans averaged 262,000 CFU/g; yeasts,F u s a r i u m , P e n i c i l l i u m , P h o m a ,Cladosporium, Alternaria, and Aspergilluswere predominant. Concentrations of fungi indrain pan water samples from AH S4averaged 215,000 CFU/g; Fusarium, yeasts,Paecilomyces, and Aspergillus werepredominant.

Air Handler Inspections in thePlant

Air handlers on the ground floor and the highvelocity unit on the rooftop were in goodcondition with no notable problems. Thefollowing observations pertain to the AHs onthe first and second floors. Most outdoor air(OA) dampers were nearly closed; two wereopen an estimated 10 to 15%. The design ofthese AHs is such that the drain pans are notlocated directly underneath the cooling coils;the floor of the AHs downstream of the coilsis recessed to form a large condensatecollection pan. This large pan is drained;condensate is pumped to the rooftop to serveas makeup water for the cooling towers. Pansare filled with a foam layer of insulationabout one to two inches thick. Condensateaccumulates in this pan on top of the foam


layer. All dry drain pans exhibited a layer ofblack to brown flaky debris which was acombination of flaking foam and microbialcontamination. Most drain pans containedone or two chemical pads designed to leachbiocide into the drain pan water. Two AHshad rotating disk humidifiers attached toreturn air ducts; two others had water spraywands inserted into drain pans. Roll-type airfilters were of low efficiency (estimated lessthan 30%), were not clogged, and wereadvanced by static pressure gauge readings.Maintenance crews clean AHs annuallybefore the cooling season and performscheduled maintenance checks up to twotimes per week.

Dust Concentrations

No airborne dust concentrations exceededOSHA or ACGIH exposure limits forPNOR/C. Unless otherwise noted,concentrations are based on full-shift TWAexposures (in milligrams dust per cubic meterair, mg/m3). Area airborne dustconcentrations at sample locations 1 and 5(Figure 1) ranged from 0.11 to 0.13 mg/m3

total dust; 0.064 to 0.082 mg/m3 respirable.Closer to blowout operations at location 4, thetotal dust concentration was 0.24 mg/m3 total,0.082 respirable.

A partial shift sample was collected for 17minutes at location 2, about 10 feet fromblowout of delivery point bar code sorter #13.The partial shift total dust concentration was2.0 mg/m3 total, 0.94 respirable.

Qualitative aerosol concentrations weremeasured with a real-time aerosol monitoroperated parallel in time to vacuuming andblowout of delivery point bar code sorters #7and #13. The monitor was positionedapproximately 10 feet from, and in betweenthe delivery point bar code sorter machines(Figure 1, locations 2 and 3) at a height offive feet. Time and concentration graphs

during vacuum and blowout of delivery pointbar code sorters #7 (Figure 2) and #13 (Figure3) indicate that paper dusts aerosolized bycompressed air increase in concentrationrapidly and settle rapidly. Dustconcentrations in close proximity to blowoutincreased from 100 to 1000 times above dustconcentrations during vacuuming.

Particle Size Distributions(Gravimetric)

Only samples from locations 1, 2, 4, and 5(Figure 1) had sufficient mass per stage forsize distribution calculations; the sample fromlocation 3 (during blowout of delivery pointbar code sorter #7) was voided due toinsufficient mass on some impactor stages.Most of the mass of airborne particulatesampled during blowout of delivery point barcode sorter #13 exceeded 10 micrometers(µm) in aerodynamic diameter. Therefore,most of the mass was not of respirable size.Approximately 27 % of the mass of airborneparticulate from the blowout was below 10µm in aerodynamic diameter, therefore in therespirable fraction. The blowout sample hada mass median aerodynamic diameter(MMAD) of 19 µm, with a geometricstandard deviation (GSD) of approximately3.7. Close to delivery point bar code sorterblowout operations (Figure 1, location 4),20% of the mass was respirable, with aMMAD of 19 µm and a GSD of 2.6.Aerodynamic diameters were morepolydisperse farther away from delivery pointbar code sorter blowout. In location 5, 36%of the mass was respirable, with a MMAD of16 µm and a GSD of 4.3. About 300 feetfrom blowout at location 1, 47% of the masswas respirable, with a MMAD of 8 µm and aGSD of 6.8.23 See Table 1 for massdistribution data by aerodynamic diameter.


Aerosol and Bulk DustMicroscopy

See the Appendices for particle descriptions,electron micrographs, and particle sizedistribution data.

Medical

Community PractitionerInterviews

Two local medical practitioners wereinterviewed via telephone prior to the HHEinvestigators’ arrival in Omaha. They wereasked about increased numbers of respiratorycomplaints in postal workers and in thepopulation in general. This information wassought in order to serve as a comparison forthe incidence and prevalence of respiratorydisease between the community and the postalworkers. One of the practitioners who is apulmonary specialist, had not noted anyincrease in respiratory problems, includingasthma, in the area other than what wasexpected for that time of the year with theprevailing weather conditions. She currentlywas treating only a single employee of theOMPDC. A general practitioner who treatedpostal employees had not noted any increasein incidence or prevalence of respiratorydisease or asthma in his practice.

Worker Interviews

Of approximately 897 mailhandlers, clerks,and maintenance personnel, 14 self-selectedindividuals participated in worker interviews

with the NIOSH physician; 11 did so inperson, and 3 via telephone. Work histories,current symptoms, and medical histories werediscussed during the interviews. The numbersof individuals who presented for interviewsrepresented less than 1.6% of the work force.The sample was not considered to be randomor representative. Half of the respondentswere female. The respondents ranged in agefrom 31-67 years of age, with a median age of50 years. Forty-two percent (6/14) of theindividuals were smokers, or ex-smokers.The majority of respondents (5/14) worked onthe second floor of the plant. Respondentsrepresented various job categories such asmailhandler, clerk, flat-sorter, generalexpediter, and union official.

Postal workers were asked general questionsregarding their health and any recent orchronic respiratory illnesses that theybelieved were work related. Of thoseinterviewed, complaints centered on the upperrespiratory system. Seventy-nine percent(11/14) of respondents complained of upperrespiratory symptoms of congestion, nasaldischarge, post nasal drip and recurrent sinusinfections. Six complained of allergicsymptoms such as scratchy throat and itchyeyes. There was a single complaint each ofasthma, skin rash, and fungal lung infection.

The physician walked through the plant andinitiated discussion of work related healthsymptoms with several groups of workers.Many workers complained of upperrespiratory allergic symptoms (itchy throatsand eyes) as well as recurrent sinusitis.

Medical Records

Incomplete medical records were supplied byone individual. His records from a pulmonaryspecialist attributed his recurrentexacerbations of sinus infections andperennial allergic rhinitis to exposure toheavy allergen loads. That individual was


also known to have asthma prior to beginningwork at the post office. The pulmonaryspecialist could not say if the exposure hadoccurred in the work place since a site visitwas not made. The pulmonary specialistcould not comment on the permanence of anyrespiratory difficulty the patient may have.

A letter supplied by an ENT physician statedthe belief that there was a contribution to thepatient’s condition from the dust at the workplace. However, no permanent impairmentresulted.

Accident and Illness Reports

Review of the accident and illness reportsfrom 1993-1997 showed only one report of aproblem coded as a "respiratory condition dueto a toxic substance." No workerscompensation claims had been filed forrespiratory illness.

DISCUSSIONCellulose, a substance which is a naturalpolysaccharide widely distributed in natureand a large component of paper, is consideredto be biologically non-toxic. Airbornecellulose dust has been described as bothnon-irritating and non-toxic with little adverseeffects on the lung at concentrations of lessthan 10 mg/m3.7

Most of the studies showing adverse healtheffects of paper dust have been done in papermills where concentrations of airborne dustare 15 to 20 mg/m3.24,25 One study, done inBritish Columbia, in a soft paper mill withpaper dust levels under 10 mg/m3, showed noincrease in the prevalence of lower or upperrespiratory symptoms.26

Studies of lower levels of dust exposure (1 to3 mg/m3) in soft paper mills showed anincrease in complaints of nasal irritation and

nasal crusts, but no increase in coughing,chronic bronchitis, asthma, dyspnea orsinusitis. However, there is some evidencethat sinusitis can be induced or exacerbatedby occupational exposures. A possiblemechanism is the impaired clearance ofmucous from the nasal passages as a result ofswelling of the nasal mucosa secondary toallergic or irritant rhinitis.27 There was nodecline in respiratory function noted after lowlevels of exposure.28,29,30 Pulmonary functiontests did not show any changes in lungfunction for workers exposed to dust levelsless than 5 mg/m3 for greater than ten years.Though there was an increase in theprevalence of upper respiratory symptomswith dust exposure, no dose-responserelationship could be found.31

A study of other types of dust exposures hasshown an association between an increasedrate of upper respiratory symptoms andvarious types of non-specific occupationaldusts. Interestingly, this study also showed ahigher prevalence of upper respiratorysymptoms in never-smokers than in currentsmokers.32 It has been suggested in otherstudies that this phenomenon is probably dueto impaired mechanisms of mucosal clearancein smokers, so that they do not exhibit upperrespiratory symptoms as seen in non-smokers.27

Most OMPDC workers that were interviewedhad medical complaints which involved theupper respiratory system. Problems such asallergic rhinitis, recurrent sinusitis, itchy eyesand throat as well as nasal congestion anddischarge were common. Rare complaints oflower respiratory symptoms were also made.It is difficult to make conclusions based onthe small percentage of individualsinterviewed. It is also difficult to separate outthe effects of smoking from those ofoccupational dust exposure. It is of interest tonote that there were a larger number (9/14) ofworkers who suffered recurrent sinusitis


among the current and ex-smokers. Howeverit is important to note that since the number ofworkers interviewed were too small and notrandomly selected, valid generalizedconclusions are difficult to make.

OSHA paper dust sampling data obtained inJuly 1996 from areas in the annex and 2nd

floor plant indicate that 8-hour TWA paperdust concentrations are 0.08 mg/m3 in the boxmaking area, and range from 0.06 to 0.54mg/m3 near culling and delivery point barcode sorter areas. Partial shift samplescollected for about 80 minutes in proximity toblowout ranged from 0.34 to 0.61 mg/m3.Neither OSHA nor NIOSH exposure dataobtained at OMPDC exceed PNOR/Cexposure limits.

As determined by a literature search forreferences on the subject, health effectsassociated with exposure to paper dustgenerated from mail handling are not wellcharacterized. A basis for limiting exposureto the paper dust in mail handlingenvironments is impeded by the variability inthe sources of paper dust. Because paper dustis likely to vary widely in composition, theACGIH PNOC standard cannot be appliedwith certainty to all types of paper dusts. It isnot certain that the PNOR standard, thecellulose content of paper, or of any othersubstance and/or impurity is appropriate forlimiting exposure to paper dust. Many typesof dust exposures are without applicableexposure limits. For example, fungiconcentrations were significantly elevated(compared to outdoor levels) in the annexduring mail sack stacking. However, there arepresently no quantifiable exposure limits forfungi.

The question of what kind of respirator isacceptable for non-specific dusts has beenraised by OMPDC employees. OMPDCmanagement does not have a respiratoryprotection program and does not consider

paper dust exposures at OMPDC to besufficiently elevated to warrant the use ofrespiratory protection because paper dustexposures, even during mail sorter cleaning,are well below the PNOR standard. However,some employees have linked paper dustexposures to their own respiratory problems.

According to an OSHA interpretation letteron dust exposure of Postal employees datedSeptember 25, 1990, “certain individuals whoare allergic to non-specific dusts should beallowed to wear protective dust masks.” If aworker’s private physician “prescribes a dustmask” then “a letter from his/her privatephysician explaining the individual’ssusceptibility should be placed on file in theHealth Unit.” According to the interpretationletter, “OSHA policy is not to cite anemployer for lack of a respiratory protectionprogram unless there is a potential foremployee over exposure or an adverse healthcondition occurs due to the respirator.Therefore, the use of disposable dust masks tolimit exposure to low levels of nuisance dustswould not, in itself, necessitate the need for arespiratory protection program.”33 Thisexemption from a written respiratoryprotection program is repeated in the

1998 OSHA respiratory protection final rulewith clarification that a disposable dust maskis a “filtering facepiece (dust mask).”34

According to the 1998 OSHA respiratoryprotection final rule, even if exposures don’trequire use of respirators because exposuresare below applicable limits, employers mayprovide respirators or allow employees to usetheir own respirator. The employer mustensure that the respirators in use do notpresent a hazard to the health of employees.If only filtering facepiece respirators arevoluntarily worn, the employer is not requiredto implement a written respiratory protectionprogram. According to OSHA, it is theemployer who must rely on “professional


judgement and available data sources whenselecting respirators for protection againsthazardous chemicals that have no OSHAPEL.” According to OSHA, it is prudent toselect more rather than less protectiverespirators.33,34

CONCLUSIONSOn the basis of environmental and medicalinformation obtained during the survey,NIOSH investigators did not find clearevidence that employee symptoms werecaused by microbial contaminants or paperdust. NIOSH investigators could find nopublished research that indicated that paperdust at levels less than 5 mg/m3 generated bypaper manufacturing is a recognizedrespiratory hazard, although the type of paperdust generated by mail handling and sortingwas not the subject of any published research.Research is available that supports theoccurrence of upper respiratory symptoms(nasal crusts, congestion, rhinitis, itchy throat) at paper dust levels less than 3 mg/m3.

This does not mean that there is no basis forrespiratory health effects experienced bythose workers exposed to non-specific dustsor paper dust; nor does it invalidate workerrequests for respiratory protection, based onthe advice and direction of personalphysicians, or based on respiratory symptomsexperienced by workers.

Paper dust blowout involves relatively short-term, elevated paper particulate exposures inthe areas immediately surrounding blowout.Most of the particulate settles quickly and isnot of respirable size. Paper dust hasaccumulated on surfaces within the plant,particularly the return air grates leading to airhandlers.

Airborne fungal spore concentrations in theplant were not significantly elevated

compared to outdoor concentrations. Fungicultured from bulk paper dust collected fromthe inside of sorters are common in indoorand outdoor environments. Compared to bulkdusts collected from a return air grill, freshlygenerated paper dust is not a significantsource of fungi in the plant. Fungi were about60 to 100 times more concentrated in the dustunder the return air grate of AH S3 comparedto freshly generated paper dust. Many fungalspecies in return air grate dust and from drainpan samples favor moist conditions forgrowth. The cellulose content of paper dustprovides a good food source for fungi, andpaper dust absorbs moisture from the air. Theaccumulation of bulk paper dust will likelyprovide a matrix for fungal growth, andappears to be a significant source of fungalmaterial, specifically Aspergillus, Penicillium,and yeasts. However, a significantly elevatedconcentration of airborne fungalcontamination was not measured in the plantduring this evaluation. Airborne fungi,particularly Aspergillus/Penicillium, weresignificantly elevated in the annex, whencompared to outdoor levels, during mail sackhandling and stacking.

Overall, AHs were in good mechanicalcondition. However, drain pans,humidification units, and metal panels withinAHs did not appear to be free of accumulateddebris. Some drain pans were filled withwater; these pans should drain rapidly enoughnot to accumulate water. In some cases, AHswere dusty inside. The most likely cause islow filtration efficiency afforded by the roll-type filters in use, which do not prevent theaccumulation of debris in drain pans andinterior AH surfaces. The foam in the drainpans holds moisture within the drain pans,and is friable, which inhibits the aggressivecleaning of drain pan surfaces. Biocidepackets used in the drain pans were noteffective in preventing the accumulation ofmicrobial materials in the pans; these packetsare not effective unless a sufficient pool of


water in the pan enables the biocide todissolve evenly throughout the pan. Sincepans should not accumulate water and shoulddrain rapidly, the use of biocide packets is notrecommended.

Since workers were concerned about exposureto inks used by sorting machines to spray barcodes on mail, MSDSs for inks in use werereviewed to determine if exposures to the inkscould be considered a hazard. The inks arevery quick drying; considering the air dilutionvolume for the volatile fraction of the inksand their use within enclosed machinery,workers not directly handling bulk inkcontainers were judged not to be exposed to asignificant health risk. Workers who directlyhandle inks should follow the guidelines inthe MSDSs regarding personal protectiveequipment and engineering controls.

RECOMMENDATIONSIn a letter dated July 23, 1997, to OMPDCmanagement, an OSHA area directorobserved that “employees with pre-existingrespiratory ailments such as seasonalallergies, chronic asthma, [or] bronchitis areroutinely exposed to paper dusts that initiateor aggravate these health conditions.” In theletter, OSHA recommended controls thatinclude respiratory protection, smokingcessation, administrative rotation, and/orengineering solutions which minimize dustgeneration at the optical character readerdelivery point bar code sorter areas with airfiltration or wet vacuuming of surfaces.35

The following NIOSH recommendationsfocus on the control of non-specific and paperdust exposures, control of paper dustaccumulation within the plant, andmaintenance of HVAC system components:

Control of Non-specific Dust Exposures

NIOSH investigators agree with OSHA thatconcentrations of certain non-specific dusts orpaper dust can be elevated at times at theOMPDC such that dusts might initiate oraggravate pre-existing respiratory conditions.Examples of activities that were assessed byNIOSH that resulted in elevated dust levelsinclude mail sack handling (in terms of fungiconcentrations) and paper dust blowout (interms of short-term elevated dustconcentrations). We further agree withOSHA recommendations to providerespiratory protection for employees withchronic respiratory conditions, provide asmoking cessation program for affectedindividuals, and experiment with permanentadministrative job rotations for affectedworkers.

According to OSHA, if the employer decidesthat voluntary respirator use is permissibleand will not present a hazard to the health ofthe employee, the employer is responsible forselecting the type of respirator facepiece andfilter. According to the latest OSHA FinalRule for Respiratory Protection, selection isdetermined by “informed professionaljudgement” and “available data sources.”34

Filter selection is straightforward, even if themass median aerodynamic diameter (MMAD)of the particulate is not known; any Part 84filter may be used. If a physician prescribesa “dust mask”, then a respirator which uses aPart 84 filter is a good selection. A loose-fitting filtering facepiece respirator is a goodfirst choice for respiratory protection againstnon-specific dust exposures that initiate oraggravate employee health conditions.Because of their higher efficiency against 0.3micron particulate, Part 84 filters are a goodchoice for these respirators. Part 84 filtersprovide from 95 to 99.97% efficiency in theremoval of 0.3 micrometer particles. AfterJuly 10, 1998, non-powered, air-purifying,


particulate-filter respirators should beapproved under Part 84.36

If respiratory symptoms are not controlledwith a loose-fitting filtering facepiecerespirator, then a tighter-fitting filteringfacepiece respirator should be selected in theproper size for the worker’s face. Theserespirators are specially molded to form amore complete seal with the face. Ifsymptoms persist with a tight-fitting filteringfacepiece respirator that has been fit tested forthe worker, then respirators whichprogressively minimize facepiece penetrationshould be selected.

If any respirator other than a filteringfacepiece respirator is used, the employermust implement a medical evaluation toensure that the worker is medically able towear the respirator, and ensure that therespirator is cleaned, stored, and maintainedso that its use does not present a health hazardto the worker.33,34

It is important to note that the level ofprotection provided by a negative-pressurerespirator without a fit test could be anyvalue. The level of protection provided by anegative-pressure respirator will be moredependent on the quality of the fit testing thanon the respirator. When respirators are usedvoluntarily without fit testing (or othertraining) no level of protection is assured.

Control of Paper Dust Exposures

According to the NIOSH Guide to theSelection and Use of Particulate RespiratorsCertified Under 42 Part 84, Part 11 dust/mist(DM) or dust/fume/mist (DFM) filters may beused for protection against dusts with aMMAD of greater than 2 micrometers.Therefore, DM or DFM filters under Part 11may be used when necessary to protectemployees from paper dust exposures at theOMPDC since the MMAD of paper dust at

the facility is greater than 2 micrometers. Inaddition, any Part 84 filter may be used. Other respirator selection logic should followthat of non-specific dusts as outlined above.


Control of Paper Dust Accumulation

In a letter to the OMPDC dated July 23, 1997,OSHA suggests engineering control ofairborne paper dust in the form of auxiliaryair filtration or wet vacuuming of floors ormachines to remove paper dust. NIOSHinvestigators encourage the control of paperdust accumulation within the building on thegrounds that paper dust provides a goodmatrix for microbial growth, and microbialgrowth, particularly within HVAC systems,should be minimized. Ideally, paper dustshould be controlled at the source to preventaccumulation within the building. At aminimum, its accumulation should becontrolled within HVAC return and supplyairstreams. Control by prefilters, increasedefficiency of primary filters, and preventionof filter blow-by are some options. NIOSHinvestigators do not encourage the applicationof water to collect paper dust unlessmoistened surfaces are dried within 24 hours.

HVAC Systems

1. Water should be removed from HVACsystems, when possible. Eliminate standingwater in air handling systems by providingfree-flowing drains.

2. To help minimize the accumulation ofdebris within air handlers, ensure all HVACsystems have OA filters that are securelyfastened into filter racks that minimizeblow-by of unfiltered air. Filters should be 50to 70% efficient (according to the AmericanSociety of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) dust spotefficiency test) in order to remove mostmicrobial particulate from the airstream.Upgraded filters should be within the limit ofpressure drop the systems can handle.

3. Clean and disinfect humidifiers andmechanical components on a routine basis, asrecommended by equipment manufacturers.

Avoid the use of water sprays in HVACsystems. Water containing biocide residuesor water treatment chemicals should never beused for humidifying. The porous and friablefoam in the drain pans is not conducive toaggressive cleaning and will likely becomecontaminated unless regularly cleaned anddisinfected. Drain pan should not accumulatewater, thus rendering the use of biocidesunnecessary. Cleaning should be performedoften enough to prevent the accumulation ofslime in drain pans. When cleaning andsanitizing HVAC components, never disinfector use biocides in water or air in an operatingHVAC system. Ensure that the HVACsystem is not operating until it is cleaned,sanitized, and dried. Loosen and removemold, slime, dirt, and organic debris, thensanitize using a dilute aqueous householdbleach solution (10% bleach in water).Bacterial endospores, produced by somethermophilic actinomycetes, may be slightlyresistant to chlorine disinfectants; therefore,surfaces should be kept moist with the bleachsolution for a sufficient contact time to allowfor disinfection to occur (about 10 to 15minutes). A clean water rinse should followcleaning and sanitizing.

4. Since all OA intakes were nearly closed,the NIOSH investigators suspect that OArequirements are not known. Current designair flow controls should be verified by anengineering firm. The firm should adjust allHVAC systems to ensure that they willoperate such that ASHRAE recommendedstandards are satisfied. These ASHRAEstandards include recommended outdoor airflow per occupant, and seasonalrecommended limits for indoor temperatureand relative humidity. Any changes in thesystems which affect current designs shouldbe recorded as an addendum to existingHVAC documentation.

5. The floor of fan rooms, including surfacesunderneath the air handlers, should be kept


free of debris which could become entrainedinto the supply air stream.

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17. Weiss NS, Soleymani Y [1971].Hypersensitivity lung disease caused bycontamination of an air-conditioning system.Annals of Allergy 29:154-156.

18. Hodgson MJ, Morey PR, Attfield M,Sorenson W, Fink JN, Rhodes WW,Visvesvara GS [1985]. Pulmonary diseaseassociated with cafeteria flooding. Archivesof Environmental Health 40(2):96-101.

19. Fink JN, Banaszak EF, Thiede WH,Barboriak JJ [1971]. Interstitial pneumonitisdue to hypersensitivity to an organismcontaminating a heating system. Annals ofInternal Medicine 74:80-83.

20. Banazak EF, Barboriak J, Fink J, ScanlonG, Schlueter EP, Sosman A, Thiede W, UngerG [1974]. Epidemiologic studies relatingthermophilic fungi and hypersensitivity lungsyndrome. American Review of RespiratoryDisease 110:585-591.

21. Kaliner M, Eggleston PA, Mathews KP[1987]. Rhinitis and asthma. Journal ofthe American Medical Association258(20):2851-2873.

22. Jordan FN, deShazo R [1987].Immunologic aspects of granulomatous andinterstitial lung diseases. Journal of theA me r i c a n M e d i c a l A s s o c i a t i o n258(20):2938-2944.

23. Hinds WC [1982]. Aerosol technology.New York, NY: John Wiley & Sons. pp 211-233.

24. Toren K, Sallsten G, Jarvholm B [1991].Mortality from asthma, chronic obstructivepulmonary disease, respiratory system cancer,and stomach cancer among paper millworkers: a case-referent study. AmericanJournal of Industrial Medicine 19:729-737.

25. Thoren K, Jarvholm B, Morgan U[1989]. Mortality from asthma and chronicobstructive pulmonary disease among workersin a soft paper mill: a case-referent study.British Journal of Industrial Medicine 46:192-195.

26. Chan-Yeung M, Wong R, Maclean L,Tan F, Dorken E, Schulzer M, Dennis R,Grzybowski S [1980]. Respiratory survey ofworkers in a pulp and paper mill in powellriver, british columbia. 122:249-257.

27. LaDou J, ed. [1997]. Occupational andenvironmental medicine. 2nd ed. Stamford,Conn.: Appleton & Lange.

28. Ericsson J, Jarvholm B, Norin F [1988].Respiratory symptoms and lung functionfollowing exposure in workers exposed to softpaper tissue dust. 60:341-345.

29. Gaertner M, Brunstein C, Busetto A[1992]. Lung function and respiratorysymptoms in paper industry workers exposedto soft paper tissue (bathroom tissue) dust.Archives des maladies professionnelles.53(7):639-644.


30. Toren K, Jarvholm B, Sallsten G,Thiringer G [1994]. Respiratory symptomsand asthma among workers exposed to paperdust: a cohort study. 26:489-496.

31. Toren K, Sallsten G, Bake B, Drake U,Jarvholm B, Sahle W [1989]. Lung functionand respiratory symptoms among workers ina soft paper mill. 61:467-471.

33. Korn RJ, Dockery DW, Speizer FE,Ware JH, Ferris BG [1987]. Occupationalexposures and chronic respiratory symptoms;a population-based study. Am Rev Respir Dis136:298-304.

34. OSHA [1990]. Interpretation; Dustexposure for postal employees. U.S.Department of Labor, Occupational Safetyand Health Administration.

34. 63 Fed. Reg. 5 [1998]. OccupationalSafety and Health Administration: respiratoryprotection; final rule. (Codified at 29 CFR1910 and 1926).

35. Office of OSHA Area Director LodamaDelinger [1997]. Letter to David J. Hayek,Acting Senior Manager, U.S. Postal Service,Omaha, Nebraska. Des Moines, Iowa.Photocopy.

36. NIOSH [1996]. NIOSH guide to theselection and use of particulate respiratorscertified under 42 CFR 84. Washington, DC:U.S. Department of Health and HumanServices, Public Health Service, Centers forDisease Control and Prevention, NationalInstitute for Occupational Safety and Health,DHHS (NIOSH) Publication No. 96-101.

Table 1Particle Size Distribution Data From Locations In the Plant

Omaha Mail Handling and Distribution Center, Omaha, Nebraska


HETA 98-0017-2699

Sampling Location Impactor StageNumber

Median StageCutoff Size forParticles (µm)

Cumulative PercentMass Less thanParticle Size

North 2nd FloorISS Stacker AreaGrid Location E13

12345678

Final

2115106

3.52

0.90.50.25

74.764.247.444.236.825.318.94.20

Central 2nd FloorECA DSS AreaGrid Location E8 / E9

12345678

Final

2115106

3.52

0.90.50.25

59.333.519.88.24.93.33.32.70

Southeast 2nd FloorDelivery Point Bar CodeSorter Staging AreaGrid Location H6

12345678

Final

2115106

3.52

0.90.50.25

72.155.836.012.811.65.85.82.30

Southwest 2nd FloorECA Delivery Point BarCode Sorter (Phase II)190 Stacker #13BlowoutGrid Location A5.5 /B5.5

12345678

Final

2115106

3.52

0.90.50.25

49.047.126.522.110.34.4000


Figure 12nd Floor Plant Airborne Dust Sampling Locations (1 - 5)

Omaha Mail Handling and Distribution Center, Omaha, NebraskaHETA 98-0017-2699


Figure 2Graph of Qualitative Aerosol Concentrations During

Vacuum / Blowout of Delivery Point Bar Code Sorter #7, January 27, 1998Omaha Mail Handling and Distribution Center, Omaha, Nebraska

HETA 98-0017-2699


Figure 3Graph of Qualitative Aerosol Concentrations During

Vacuum / Blowout of Delivery Point Bar Code Sorter #13, January 27, 1998Omaha Mail Handling and Distribution Center, Omaha, Nebraska

HETA 98-0017-2699


APPENDICESCellulose was a predominant particle observed in both settled dust and air samples collected in thesecond floor plant. Polarized light microscope images of settled dust collected on surfaces ofdelivery point bar code sorter #6 revealed birefringent, predominantly fibrous particles as cellulose.Cellulose fibers were rather tightly curled and knotted.

Figure 1 contains scanning electron microscope images of the same material. Although cellulosefibers are characteristically twisted, the degree of curling seen here is considered unusual and mayperhaps be due to forces applied to the letters as they are fed through the delivery point bar codesorter.

Particle images of airborne dust obtained 10 feet from delivery point bar code sorter #7 duringblowout indicate many of the airborne particles are non-fibrous. Observation of optical features ofthese particles under polarized light microscopy indicate that many of these particles are cellulose.Although less frequent than in the settled dust samples, particles with a curled or knotted structurewere also observed in the air samples. The relative scarcity of these particles in air samples is likelydue to the fact that tightly curled particles would have larger aerodynamic diameters and thus bemore likely to settle-out close to their point of generation.

Figure 2 provides a graphical representation of the length and width distributions for measurementsmade on an air sample collected 10ft from delivery point bar code sorter #6 during blowout. Allparticles with a length to width ratio > than 3:1 were sized. Measurements were made usingscanning electron microscopy at a magnification of 2000X. Mean width was 3.3 µm (standarddeviation 2.6). Average length was 18.9 µm with a standard deviation of 17.6. The particle lengthsspanned an order of magnitude (<10 to >100 µm). Differential counts indicated that only about 20%of the particles detected would be considered fibers under the 3:1 criterion. As mentioned, manyof the non-fibers are cellulose-based particles. Some of the other types of particles observed in thesesamples include starch grains, skin cells and minerals.

A limited number of samples were also collected in the annex. Light and electron microscopicobservation of these samples indicated a different sort of aerosol. Cellulose particles are ubiquitousand some were detected. The predominant particles were mineral based. Large particlesrepresentative of much of the particulate were birefringent and X-ray analysis indicated apredominant calcium peak. The warehouse is a concrete structure and these observations areconsistent with the generation of concrete particles as bags of mail are dragged across the floor.Smaller particles were present forming an agglomerate of very small roughly spherical particles.Knowledge of the operation of diesel trucks delivering mail to this warehouse provides a strongargument that these particles are diesel combustion products.

1.

2.

3.

Delivering on the Nation’s promise:Safety and health at work

For all peopleThrough research and prevention

4.

5.OSHA [1993]. Interpretation; Compliance and enforcement activities affected by the PELs decision.U.S. Department of Labor, Occupational Safety and Health Administration.

6.Tingle R [1998]. Telephone conversation on March 23, 1998 between R. Tingle, Directorate of HealthStandards Programs, Occupational Safety and Health Administration, Department of Labor, and D.Hewett, Division of Respiratory Disease Studies, National Institute for Occupational Safety and Health,Centers for Disease Control, Public Health Service, U.S. Department of Health and Human Services.

7.ACGIH [1991]. Documentation of the threshold limit values and biological exposure indices. 6th ed.Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

8.R Rylander, RR Jacobs eds. [1994]. Organic dusts: exposure, effects, and prevention. Ann Arbor, MI:Lewis Publishers, p. 45.

9.Burge HA [1988]. Environmental allergy: definition, causes, control. Engineering Solutions to IndoorAir Problems. Atlanta, GA: American Society of Heating, Refrigeration and Air-ConditioningEngineers, 3-9.

10.Morey MR, Feeley JC [1990]. The landlord, tenant, and investigator: their needs, concerns andviewpoints. Biological Contaminants in Indoor Environments. Baltimore, MD: American Society forTesting and Materials, pp 1-20.

11.Pickering CA [1992]. Immune respiratory disease associated with the inadequate control of indoor airquality. Indoor Environment 1:157-161.

12.Molhave L, Bach B, Pedersen OF [1986]. Human reactions to low concentrations of volatile organiccompounds. Environ Int 12:167-176.

13.Vinken W, Roels P [1984]. Hypersensitivity pneumonitis to Aspergillus fumigatus in compost. Thorax 39:74- 74.

14.Malmberg P, Rask-Andersen A, Palmgren U, Höglund S, Kolmodin-Hedman B, Stålenheim G [1985]. Exposure to microorganisms, febrile and airway-obstructive symptoms, immune status, and lung functionof Swedish farmers. Scandinavian Journal of Work and Environmental Health 11:287-293.

15.Topping MD, Scarsbrick DA, Luczynska CM, Clarke EC, Seaton A [1985]. Clinical andimmunological reactions to Aspergillus niger among workers at a biotechnology plant. British Journal ofIndustrial Medicine 42:312-318.

16.Edwards JH [1980]. Microbial and immunological investigations and remedial action after anoutbreak of humidifier fever. British Journal of Industrial Medicine 37:55-62.

17.Weiss NS, Soleymani Y [1971]. Hypersensitivity lung disease caused by contamination of anair-conditioning system. Annals of Allergy 29:154-156.

18.Hodgson MJ, Morey PR, Attfield M, Sorenson W, Fink JN, Rhodes WW, Visvesvara GS [1985]. Pulmonary disease associated with cafeteria flooding. Archives of Environmental Health 40(2):96-101.

19.Fink JN, Banaszak EF, Thiede WH, Barboriak JJ [1971]. Interstitial pneumonitis due tohypersensitivity to an organism contaminating a heating system. Annals of Internal Medicine 74:80-83.

20.Banazak EF, Barboriak J, Fink J, Scanlon G, Schlueter EP, Sosman A, Thiede W, Unger G [1974]. Epidemiologic studies relating thermophilic fungi and hypersensitivity lung syndrome. AmericanReview of Respiratory Disease 110:585-591.

21.Kaliner M, Eggleston PA, Mathews KP [1987]. Rhinitis and asthma. Journal of the AmericanMedical Association 258(20):2851-2873.

22.Jordan FN, deShazo R [1987]. Immunologic aspects of granulomatous and interstitial lung diseases. Journal of the American Medical Association 258(20):2938-2944.

23.Hinds WC [1982]. Aerosol technology. New York, NY: John Wiley & Sons. pp 211-233.

24.Toren K, Sallsten G, Jarvholm B [1991]. Mortality from asthma, chronic obstructive pulmonarydisease, respiratory system cancer, and stomach cancer among paper mill workers: a case-referent study.American Journal of Industrial Medicine 19:729-737.

25.Thoren K, Jarvholm B, Morgan U [1989]. Mortality from asthma and chronic obstructive pulmonarydisease among workers in a soft paper mill: a case-referent study. British Journal of Industrial Medicine46:192-195.

26.Chan-Yeung M, Wong R, Maclean L, Tan F, Dorken E, Schulzer M, Dennis R, Grzybowski S [1980].Respiratory survey of workers in a pulp and paper mill in powell river, british columbia. 122:249-257.

27.LaDou J, ed. [1997]. Occupational and environmental medicine. 2nd ed. Stamford, Conn.: Appleton &Lange.

28.Ericsson J, Jarvholm B, Norin F [1988]. Respiratory symptoms and lung function following exposurein workers exposed to soft paper tissue dust. 60:341-345.

29.Gaertner M, Brunstein C, Busetto A [1992]. Lung function and respiratory symptoms in paperindustry workers exposed to soft paper tissue (bathroom tissue) dust. Archives des maladiesprofessionnelles. 53(7):639-644.

30.Toren K, Jarvholm B, Sallsten G, Thiringer G [1994]. Respiratory symptoms and asthma amongworkers exposed to paper dust: a cohort study. 26:489-496.

31.Toren K, Sallsten G, Bake B, Drake U, Jarvholm B, Sahle W [1989]. Lung function and respiratorysymptoms among workers in a soft paper mill. 61:467-471.

32.Korn RJ, Dockery DW, Speizer FE, Ware JH, Ferris BG [1987]. Occupational exposures and chronicrespiratory symptoms; a population-based study. Am Rev Respir Dis 136:298-304.

33.OSHA [1990]. Interpretation; Dust exposure for postal employees. U.S. Department of Labor,Occupational Safety and Health Administration.

34.63 Fed. Reg. 5 [1998]. Occupational Safety and Health Administration: respiratory protection; finalrule. (Codified at 29 CFR 1910 and 1926).

35.Office of OSHA Area Director Lodama Delinger [1997]. Letter to David J. Hayek, Acting SeniorManager, U.S. Postal Service, Omaha, Nebraska. Des Moines, Iowa. Photocopy.

36.NIOSH [1996]. NIOSH guide to the selection and use of particulate respirators certified under 42CFR 84. Washington, DC: U.S. Department of Health and Human Services, Public Health Service,Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health,DHHS (NIOSH) Publication No. 96-101.

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