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HEALTH CONSULTATION

Evaluation of Indoor Air Sampling Results
(January 29-30, 2003)

PACIFIC CLEANERS AND RANDY'S NUTRITION
OLYMPIA, THURSTON COUNTY, WASHINGTON


BACKGROUND AND STATEMENT OF ISSUES

The Washington State Department of Health (DOH), in cooperation with the Thurston CountyPublic Health and Social Services Department (TCHD) conducted an exposure investigation toevaluate whether tetrachloroethylene (PCE) and PCE-related chemicals may be present at levelsof health concern inside Randy's Nutrition Center (Randy's). Randy's is a health foods storelocated adjacent to Pacific Cleaners, an active dry-cleaning business that uses PCE. Randy's islocated at 3530 Pacific Avenue SE, in Olympia, Washington (Appendix B, Figures 1 and 2).DOH prepares health consultations under a cooperative agreement with the Agency for ToxicSubstances and Disease Registry (ATSDR).

Pacific Cleaners has a history of odor and health complaints. In October 1992, the OlympicRegion Clean Air Agency (ORCAA) was contacted by a nearby business about odor and healthconcerns associated with Pacific Cleaners.1 More recently, in December 2002 and January 2003,the owner of Randy's contacted ORCAA with similar concerns.2 Because of these recentconcerns, ORCAA conducted numerous inspections at Randy's and Pacific Cleaners, andconfirmed the reported odors. During one of the inspections, using a portable HFC (HalogenLeak Detector), PCE was detected throughout Pacific Cleaners as well as outside the open shopdoors. ORCAA also observed vapor leaks, open containers, and possible faulty temperaturegauges that resulted in a number of violation notices and at least one fine.2

Because odors continued at Randy's after ORCAA was notified, the owner also contactedTCHD. In January 2003, TCHD sampled Randy's and Pacific Cleaners using a portable photoionization detector (PID) calibrated for PCE. The PID detected contaminant vapor levels thatexceeded health comparison values in both Pacific Cleaners and Randy's.

Following the PID sampling, TCHD collected indoor air samples using 6-liter Summa®canisters with preset flow control devices that allowed time-weighted samples to be collectedover a 24-hour period. The samples were collected in the back of Randy's and in a classroomlocated between Randy's and Pacific Cleaners, from January 29-30, 2003, and were analyzed forvolatile organic compounds (VOCs), including PCE. Atmospheric Analysis & Consulting, Inc.analyzed the samples for VOCs using EPA Method TO-15.

The canister sampling indicated that measured levels of PCE, trichloroethylene (TCE),methylene chloride, and numerous other VOCs exceeded corresponding health comparisonvalues. (Table 1).4 Methylene chloride and many of the other VOCs are most likely associatedwith localized sources, such as office supplies and nearby automobile emissions.

A consultant hired by Pacific Cleaners determined that the source of the PCE was a leak at theirdry-cleaning machine. As a result of the leak, ORCAA directed Pacific Cleaners to repair theequipment. In late February, after repairs were made to correct the leak, the WashingtonDepartment of Labor and Industries (L&I) inspected Pacific Cleaners, and did not detect anyPCE.5

This health consultation evaluates the results of the Summa® canister air samples collected fromJanuary 29-30, 2003 by TCHD inside Randy's and the classroom between Randy's and PacificCleaners.


DISCUSSION

Indoor air sampling results from samples obtained in January 2003 from Randy's and theclassroom located between Randy's and Pacific Cleaners were screened using ATSDR, U.S.Environmental Protection Agency (EPA), and Washington State Department of Ecology(Ecology) health-based criteria (comparison values). Contaminant concentrations belowcomparison values are unlikely to pose a health threat, and were not further evaluated.Contaminant concentrations exceeding comparison values and background levels (chemicals ofpotential concern, or COPCs) do not necessarily pose a health threat, but were further evaluatedto determine whether they are at levels that could cause adverse human health effects.

Indoor air sampling results

Background: Background is defined here as the amount of chemical(s) expected to be present in air without any known contribution from a particular source. The background levels cited in this health consultation were obtained from various indoor air studies conducted throughout urban areas of the U.S. Sources of back ground levels of PCE, TCE, and methylene chloride can include household products, recently dry-cleaned clothes, solvents, paints, etc.Indoor air sampling results revealed that PCE and TCE levels were much higher than the concentrations of other detected chemicals, and are considered as chemicals of potential concern. PID readings revealed contaminant vapor levels from 10,000 parts per billion (ppb) to 2,000,000 ppb in Pacific Cleaners, and from 1,100 ppb to 20,400 ppb in Randy's. The highest levels were measured in and around the dry-cleaning machine, and at the rear of the dry-cleaning business, near the ceiling vent.3 It should be noted that a PID is a screening level instrument designed to provide an estimate of organic vapors present, not to precisely distinguish one ionizable gas (such as PCE) from another. Therefore, if there is more than one compound present, the PID will not provide an accurate concentration of a particular gas, only an approximate reading of total gas concentration. Results of 24-hour Summa® canister air samples revealed PCE levels from 4,617 micrograms per cubic meter (µg/m3) to over 8,000 µg/m3, while TCE levels ranged from 397 µg/m3 to 468 µg/m3 (Table 1).4

Methylene chloride and benzene were also detected above their respective health comparison values in both locations tested. However, the levels were low and were at or near background levels of these chemicals commonly present in urban indoor and ambient air (Table 1).6,7 Health risks from exposure to these two chemicals was estimated to be low, and will not be discussed further in the health consultation. A number of other VOCs were also found at low levels in indoor air. Many of these VOCs were expected, since they have many common sources, including cleaning supplies, office equipment, nail polish, paint, and gasoline among others. These other VOCs were either below health comparison values, or at background levels. As a result of these findings, only the potential health hazards posed by PCE and TCE will be discussed further in this health consultation.

Table 1.

Pacific Cleaners and Randy's Nutrition Center.Chemicals detected in indoor air exceeding health comparison values and background indoor air values, January 29-30, 2003
(Units are in micrograms per cubic meter)
Chemical Location Comparison Value Background Indoor Air Literature Values Cancer Class
Randy's back room (Summa® canister) Classroom
(Summa® canister)
Cancer Noncancer
methylene chloride 38.2 21.2 3 (CREG) 1,042
(chronic MRL)
6 EPA B2
benzene 3.2 4.8 0.1 (CREG) 30 (RfC) 10 EPA Group A
tetrachloroethylene
(PCE)
8,113 4,617 NA 271 (chronic MRL)
101,748 (LOAEL)
5
(Shah & Singh)6
NA
trichloroethylene
(TCE)
468 397 NA 40 (NCEA RfC)
37,619
(subchronic LOAEL)
0.7
(Shah & Singh)6
NA
toluene 10.6 13.6 NA 400 (RfC) 5.7
(HSDB/indoor air)
EPA Group D

Shaded cells = chemicals of potential concern further evaluated in the health consultation
NA = not available
CREG = ATSDR cancer risk evaluation guide
MRL = ATSDR minimal risk level
EPA = Environmental Protection Agency
RfC = Reference concentration
LOAEL = Lowest Observed Adverse Effect Level
Ppb = parts per billion
NCEA = National Center for Environmental Health
HSDB = Hazardous Substance Data Bank

Non-cancer effects evaluation

EPA Reference Concentration (RfC) and ATSDR Chronic Minimal Risk Level (MRL): Inhalation reference concentrations (RfCs) and chronic minimal risk levels (MRLs) are concentrations of a chemical in air below which adverse noncancer health effects are not expected to occur over a lifetime of continuous (i.e., 24-hour per day) exposure.To estimate the potential for noncancer health effectsfrom exposure to PCE and TCE,the concentrations of these two chemicals werecompared to their respectivenoncancer comparison value [EPA referenceconcentration (RfC) or ATSDRchronic minimal risk level (MRL)]. RfCs and MRLsare set well below the actual toxiceffect level (i.e., lowest observed adverse effect level(LOAEL) or no observed adverseeffect level (NOAEL) determined from those studiesupon which they are based. Thisapproach provides additional health protection toaccount for the uncertaintyassociated with setting these "safe" levels of exposure.As shown in Table 1, PCE andTCE levels in Randy's and the adjacent classroomexceed background levels andtheir respective MRL or RfC.

PCE is a manufactured compound widely used for dry-cleaning fabrics and as a metal degreaser. It is also used as an intermediate inthe manufacturing of other products. It evaporates easily into the air, and has a sharp, sweet odor at high concentrations.8 TCE isprimarily used as a metal degreaser, particularly in the automotive and metals industries. It is a breakdown product of PCE and it isalso found in some household products, such as typewriter correction fluid, paint removers, adhesives, and spot removers.9

The MRL for PCE is based upon neurobehavioral effects observed during a 10-year occupational study.8 Other systemic health effectsassociated with exposure to high levels of PCE in air include hepatotoxic (liver) effects, reversible kidney damage, endocrine effects,reproductive, and developmental effects.8, 10 TCE exposure is associated with many of the same health effects as PCE, includingneurotoxicity, immunotoxicity, developmental toxicity, liver and kidney toxicity, and endocrine effects.9,10 The RfC for TCE is based on critical effects on the central nervous system, liver, and endocrinesystem.10

While levels of PCE and TCE in indoor air exceeded their respective MRL or RfC, indicating the possibility of adverse noncancer(i.e., central nervous system, liver, and endocrine) effects from continuous, long-term exposure, it should be noted that the levels werefrom 10 to 100 times lower than the actual levels that produced these effects in the relevant occupational and laboratory animalstudies.8, 9, 10, 11, 12

Table 2.

Randy's Nutrition Center and adjacent classroom. Noncancer risks (hazard quotients) associated with chronic exposure to the maximum concentration of PCE and TCE measured in indoor air*
Chemical Location
*Hazard Quotient
(Randy's back room)
*Hazard Quotient
(Classroom)
tetrachloroethylene (PCE) 6** 3.4**
trichloroethylene (TCE) 2.3** 2**

*Correction factor of 0.2 was used in the exposure calculations to account for the less than 24-hours/day, 7-days/week exposure frequency for an office worker (see Appendix B).
**Hazard quotient greater than 1 indicates a potential noncancer health risk (see Appendix B for health risk formulas). Of the detected chemicals, PCE and TCE accounted for all of the potential noncancer risks (i.e., hazard quotient greater than 1).

Cancer risk evaluation

Tetrachloroethylene (PCE)

Although it has not been shown to cause cancer in people, the U.S. Department of Health andHuman Services has determined that PCE may reasonably be anticipated to be a carcinogen.8, 10, 12 The International Agency for Research on Cancer (IARC) has determined thatit is probably carcinogenic to humans, based on limited human evidence and sufficient evidencein animals. EPA is currently reassessing PCE toxicity, and has not adopted a final position on theweight-of-evidence classification.10, 12

Although a number of human studies (primarily epidemiology studies of dry-cleaning workers)suggest the possibility of increased cancer incidences from exposure to PCE, particularlyesophageal and bladder cancers, it has not been shown to definitively cause cancer in humans.Other cancers suspected of being associated with exposures to high levels of PCE includeintestinal, pancreatic, lung, kidney, skin, colon, and lymphatic/hematopoietic cancer. PCEincreased the incidence of hepatocellular tumors in laboratory mice after oral and inhalationexposure and mononuclear cell leukemia and kidney tumors in rats after inhalation.8, 10, 12

The California Environmental Protection Agency (Cal EPA) recently derived an inhalation unitrisk for PCE that can be used to estimate cancer risk.13 Using this value, the estimated increasedrisk of developing cancer, assuming continuous exposure over a working lifetime to the detectedconcentrations of PCE in indoor air, is from approximately two to four additional cancers in a population of 1,000 persons exposed (2 x 10-3 to 4 x 10-3) (Table 3). Actual risks are probablymuch lower than this, as exposure to these levels is more likely to have occurred over a period ofdays or weeks, not years.

Trichloroethylene (TCE)

The NCEA is currently revising a human health risk assessment for TCE that will present EPA'smost current evaluation of the potential health risks from exposure to this chemical. Themechanistic information suggests some risk factors that may make some populations moresensitive, and that TCE could affect children and adults differently.11

Recent and extensive review of available data has led EPA to characterize TCE as "highly likelyto produce cancer in humans." These findings are consistent with those of the InternationalAgency on Research of Cancer (IARC, 1995) and the National Toxicology Program (NTP,2000). This classification is based on sufficient evidence in animals and limited evidence inhumans. The strongest evidence that TCE can cause cancer in humans comes from occupationalstudies that have found increases in lung, liver and kidney cancers in workers exposed overseveral years.11

In experimental rodent studies, high doses of TCE administered to mice resulted in tumors of thelungs, liver, and testes. Other possible cancers associated with exposure to high levels of TCEinclude cancer of the bladder, stomach, prostate, kidney, and pulmonary system.9, 11 TCE cancereffects levels (CELs), which were derived from lowest observed adverse effects levels(LOAELs) in chronic-duration studies on rats and mice, ranged from 100,000 ppb to 600,000ppb.9, 11 TCE levels measured in indoor air in Randy's and the adjacent classroom werethousands of times lower than these CELs.

Although the data obtained from high-dose animal or worker exposure studies is not directlyapplicable to exposures at these businesses, theoretical cancer risk estimates can be made basedon this data. In order to estimate the increased cancer risk for persons assumed to be chronicallyexposed to the detected levels of TCE in indoor air, the current recommended EPA inhalation slope factor was used.11 The estimated increased cancer risk from TCE exposure in thetwo locations tested is similar to the risk from exposure to PCE, approximately five additionalcancers in a population of 1,000 persons exposed over a working lifetime (5 x 10-3) (Table 3).

Table 3.

Randy's Nutrition and adjacent classroom Estimated increased cancer risk associated with chronic exposure to the maximum concentration of PCE and TCE measured in indoor air*
Chemical Location
Randy's back room Classroom
tetrachloroethylene (PCE) 3.8E-3 2.2E-3
trichloroethylene (TCE) 6E-3 5E-3
Total increased cancer risk 1E-2 7E-3

*CF = 0.08 correction factor to account for the less than 24-hours/day, 7 days/week exposure frequency for an office worker (see Appendix B).
For this health consultation, a 25-year exposure duration was assumed (EPA Exposure Factors Handbook, 1997).

Data Limitations

It should be noted that the estimated exposures and risks presented above are based on the resultsof a single sampling event, and therefore may not represent levels under different conditions ortimes. The suspected source of the PCE and TCE was reportedly eliminated, so current levels arelikely much lower, or nonexistent. However, as sampling data does not exist to confirm this conclusion, DOH recommends follow up confirmatory sampling.

Chemical mixtures

It is plausible that trichloroethylene and tetrachloroethylene jointly act in an additive manner toimpair nervous system function. There is no evidence to indicate that these chemicals jointly acton the nervous system in a less-than-additive or greater-than-additive mode.14

The effect of tetrachloroethylene on trichloroethylene's liver and kidney toxicity was projectedto occur by a less-than-additive joint action based on in vivo evidence that tetrachloroethyleneinhibits the metabolism of trichloroethylene in humans under occupational exposure conditions,and evidence that trichloroethylene and tetrachloroethylene act in a less-than-additive manner tocause liver and kidney peroxisomal proliferation. In summary, the available data provide noevidence of greater-than-additive interactions among trichloroethylene or tetrachloroethylenethat might cause liver and kidney effects to occur.14

A component-based hazard index approach that assumes additive joint toxic action and usesATSDR MRLs based on neurological impairment is recommended for exposure-basedassessments of possible health hazards from exposure to mixtures of trichloroethylene andtetrachloroethylene. There is no evidence to indicate that greater-than-additive interactionswould cause liver and kidney effects to occur at exposure levels lower than those influencing thenervous system.14

Quantitative estimates (total estimated increased cancer and non-cancer risks) from exposure toall of the chemicals listed in Table 1 were also evaluated. TCE and PCE accounted for almost all of the increased risk.

Child Health Considerations

ATSDR recognizes that infants and children may be more vulnerable to exposures than adultswhen faced with contamination of air, water, soil, or food.15 This vulnerability is a result of the following factors:

  • Children are more likely to play outdoors and bring food into contaminated areas.

  • Children are shorter and their breathing zone is closer to the ground, resulting in a greater likelihood to breathe dust, soil, and heavy vapors.

  • Children are smaller and receive higher doses of chemical exposure per body weight.

  • Children's developing body systems are more vulnerable to toxic exposures, especiallyduring critical growth stages in which permanent damage may be incurred.

Laboratory animal studies involving high dose exposures to the chemicals of concern (PCE andTCE) detected in indoor air in Randy's, the adjacent classroom, and Pacific Cleaners may resultin reproductive and/or developmental effects. For example, studies of animals exposed in utero (via oral exposure of mothers) indicate that PCE can adversely influence the developing nervoussystem, but studies to examine possible associations between occupational exposure of humansto PCE and increased risks for birth defects in offspring or reproductive effects such asmenstrual disorders and spontaneous abortions provide only suggestive evidence that these typesof effects may occur in humans (ATSDR 1997).

Since direct or indirect exposures to the unborn, infants and young children inside thesebusinesses are expected to be infrequent, DOH considers the risks to be minimal. In addition, thelevels of PCE and TCE that produced developmental and reproductive effects in the relevanttoxicity studies were considerably higher than the levels detected inside the businesses.


CONCLUSIONS

A previous, short-term drycleaning machine leak inside Pacific Cleaners is the likely sourceof measured levels of PCE and TCE in Randy's Nutrition Center and a classroom situatedbetween Pacific Cleaners and Randy's. A consultant hired by Pacific Cleaners evaluated theleak, which appears to have been mitigated. As a result, current levels are likely much lower,or nonexistent.

Estimated exposures and health risks discussed in the health consultation are based on theresults of a single sampling event, and therefore may not represent levels under differentconditions or times. Based on the results of this single sampling event, an elevated health riskcould have existed in the past, assuming a twenty-five year working lifetime exposure to themeasured levels of PCE and TCE. Pending the results of follow up, confirmatory sampling,the businesses tested (Pacific Cleaners, Randy's, and the classroom) are categorized as anindeterminate public health hazard.

  1. As a result of odor complaints and health concerns expressed by the owner of Randy'sNutrition Center (Randy's), in December 2002 and January 2003, staff from the OlympicRegion Clean Air Agency and Thurston County Environmental Health Divisioninspected Pacific Cleaners and Randy's Nutrition, and conducted indoor air sampling.Screening-level sampling revealed VOCs in indoor air in Pacific Cleaners, Randy's, andan adjacent classroom situated between Pacific Cleaners and Randy's that exceededhealth comparison values.

  2. More sensitive follow-up sampling conducted on January 29-30, 2003 inside Randy'sand the adjacent classroom revealed elevated levels of PCE and TCE in indoor air.Measured levels posed no immediate or short-term health concern.

  3. The January 29-30 sampling revealed lower levels of other chemicals in Randy's and theadjacent classroom, but below or near ambient background levels and below levels ofhealth concern. Many of these chemicals were expected, since they have many commonsources, including cleaning supplies, office equipment, nail polish, paint, and gasolineamong others.

  4. Long-term exposure to PCE and TCE levels measured in indoor air during the January29-30, 2003 sampling indicates an increased cancer risk (i.e., a cancer risk significantlygreater than what is normally expected). However, this risk assumes persons wereexposed eight hours per day, five days per week, 50 weeks per year for twenty-five yearsto the maximum detected concentrations of these chemicals. Because the source of themeasured PCE and TCE levels appears to have been a short-term leak originating fromPacific Cleaner's dry-cleaning machine, the length of exposure (hence the risk) is mostlikely much lower.

  5. Long-term exposure to the maximum levels of PCE and TCE detected in indoor air couldcause mild neurological impairment and adverse effects on the liver and kidneys forpersons assumed to be exposed continuously. Although the levels exceeded theirrespective MRL and RfC, PCE levels were from 12 to 22 times lower than the lowestlevel that produced these effects in the relevant studies (the LOAEL), while TCE levelswere from 80 to 95 times lower than the LOAEL. As indicated above, because the sourceof the elevated PCE and TCE levels appears to have been a short-term leak originatingfrom Pacific Cleaner's dry-cleaning machine, the length of exposure (hence the risk) islikely much lower.

RECOMMENDATIONS/PUBLIC HEALTH ACTION PLAN

  1. Follow-up indoor air sampling has been conducted to assure that the suspected source of the PCE and TCE has been eliminated, and that current concentrations are below levelsof health concern.

    • Action Proposed

      • DOH will work closely with TCHD and the business owners to coordinateand evaluate the results of appropriate follow-up indoor air sampling inRandy's Nutrition, the adjacent classroom, and possibly Pacific Cleaners.DOH will evaluate the results of the follow-up sampling in a separatehealth consultation.

  2. Adequate ventilation should be maintained within the business work areas to promotedispersion and reduce the accumulation of chemical vapors.

    • Action Proposed

      • DOH and TCHD will discuss this with the owners/operators of Randy'sand Pacific Cleaners.

  3. Dry-cleaning equipment should be properly maintained to assure that liquid and vaporleaks do not occur.

    • Action Proposed

      • DOH will contact TCHD and ORCAA, and the owners of Pacific Cleaners toconfirm that all equipment leaks have been repaired.

PREPARERS OF REPORT

Paul Marchant
Washington State Department of Health
Office of Environmental Health Assessments
Site Assessment Section


Designated Reviewer

Robert Duff, Manager
Site Assessment Section
Office of Environmental Health Assessments
Washington State Department of Health


ATSDR Technical Project Officer

Debra Gable
Division of Health Assessment and Consultation
Agency for Toxic Substances and Disease Registry


REFERENCES

  1. Olympic Air Pollution Control Authority (OAPCA) Complaint Form: October 7, 1992.

  2. Olympic Air Pollution Control Authority (OAPCA) Complaint Forms: December 20,2002 - January 6, 2003.

  3. Thurston County Public Health and Social Services Department, Environmental HealthDivision. Sampling and inspection notes for Randy's Nutrition Center and PacificCleaners. Olympia, Washington. January-February 2003.

  4. Atmospheric Analysis & Consulting, Inc. Laboratory Analysis Report. February 11, 2003.

  5. Personal communication with Raymond (Bruce) Christian, Washington State Departmentof Labor and Industries. February 27, 2003.

  6. Shah JJ and Singh HB. Distribution of volatile organic chemicals in outdoor and indoor air. Environmental Science and Technology 1988; 22:1381-1388.

  7. Wallace LA. Comparison of risks from outdoor and indoor exposures to toxic chemicals. Environmental Health Perspectives 1991;95:7-13.

  8. Agency for Toxic Substances and Disease Registry. Toxicological Profile forTetrachloroethylene (Update). Atlanta, Georgia: US Department of Health and HumanServices; September 1997.

  9. Agency for Toxic Substances and Disease Registry. Toxicological Profile forTrichloroethylene. Atlanta, Georgia: US Department of Health and Human Services;September 1997.

  10. U.S. Environmental Protection Agency. Integrated Risk Information System (IRIS)[online] 2003 March. Available at URL: http://www.epa.gov/iris/index.html

  11. United States Environmental Protection Agency. Trichloroethylene Health RiskAssessment: Synthesis and Characterization (External Review Draft). August 1, 2001.

  12. United States Environmental Protection Agency. Superfund Technical Support Center.National Center for Environmental Assessment. Risk Assessment Issue Paper for:Carcinogenicity Information for Tetrachloroethylene. October 25, 2001.

  13. California Environmental Protection Agency, Office of Environmental Health HazardAssessment, Air Toxics Hot Spots Program Risk Assessment Guidelines, Part II,Technical Support Document for Describing Available Cancer Potency Factors,December 2002 (excerpt pertaining to tetrachloroethylene).

  14. U.S. Department of Health and Human Services, Public Health Service, Agency forToxic Substances and Disease Registry. Interaction Profile for 1,1,1-Trichloroethane,1,1-dichloroethane, trichloroethylene, and tetrachloroethylene. Draft for Public Comment May 2002.

  15. Agency for Toxic Substances and Disease Registry. Interim guidance on including childhealth issues in Division of Health Assessment and Consultation Documents. Atlanta: USDepartment of Health and Human Services, Public Health Service, July 1998.

  16. Draft Health Consultation, Indoor Air Quality Evaluation: Cadet Manufacturing Company site. Vancouver, Clark County, Washington. May 2, 2003.

APPENDIX A: FIGURES

Pacific Cleaners & adjacent businesses, Olympia, Washington

Pacific Cleaners, Olympia, Washington


APPENDIX B: HEALTH RISK FORMULAS AND EXPOSURE ASSUMPTIONS

The formulas and parameters provided below were used to conservatively estimate cancer and noncancer health risks. It is important to note that EPA RfC and IUR values, and ATSDR MRLs assume continuous exposure.

Hazard Quotient using RfCs and MRLs

HQ = Ca/(RfC or MRL) x CF

HQ = hazard quotient (unitless)
Ca = indoor air concentration (ug/m3)
RfC = Reference concentration (ug/m3)
MRL = Minimal Risk Level (ug/m3)
CF = correction factor of 0.2 (8/24 x 5/7 x 50/52) to account for the less than continuous (i.e., 8 hours/day, 5 days/week, 50 weeks/year) exposure scenario assumed for a worker.

Cancer risk using unit risk factors

Cancer risk = Ca x IUR x CF

Ca = indoor air concentration (ug/m3)
IUR = inhalation unit risk (per ug/m3)
CF = correction factor of 0.08 (8/24 x 5/7 x 50/52 x 25/75) to account for the less than continuous (i.e., 8 hours/day, 5 days/week, 50 weeks/year, 25 years) exposure scenario assumed for a worker.

Cancer risk using slope factors

Cancer risk = ((Ca /1000) x IR x EF x ED/(BW x AT)) x CSF

Ca = indoor air concentration in micrograms/m3
IR = inhalation rate (adult worker - 10.4 m3/day)
EF = exposure frequency (250 days/year)
ED = exposure duration (25 years)
BW = body weight (72 kg)
AT = averaging time (27,375 days)
CSF = chemical-specific cancer slope factor


CERTIFICATION

This Health Consultation was prepared by the Washington State Department of Health under acooperative agreement with the Agency for Toxic Substances and Disease Registry (ATSDR). Itis in accordance with approved methodology and procedures existing at the time the healthconsultation was begun.

Debra Gable
Technical Project Officer,
SPS, SSAB, DHAC
ATSDR


The Division of Health Assessment and Consultation, ATSDR, has reviewed this public health consultation and concurs with the findings.

Sven E. Rodenbeck
for Roberta Erlwein
Chief, SPS, SSAB, DHAC
ATSDR



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