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HEALTH CONSULTATION

Evaluation of PCE and TCE in Residential Indoor Air

PALERMO WELL FIELD GROUND WATER CONTAMINATION
TUMWATER, THURSTON COUNTY, WASHINGTON


BACKGROUND AND STATEMENT OF ISSUES

DOH prepared this health consultation in response to a request from the U.S. EnvironmentalProtection Agency (EPA) to evaluate the results of indoor air samples collected at seven residenceslocated within the Palermo Wellfield Superfund site (site) in Tumwater, Washington. DOHprepares health consultations under acooperative agreement with the Agency forToxic Substances and Disease Registry.

The site includes the wellfield and the Palermoneighborhood, both located in the DeschutesRiver Valley, and the commercial area to thewest. The Palermo Wellfield consists of sixwells that provide up to 50% of the drinkingwater for the city of Tumwater. The sampleswere taken to determine whether residents arebeing exposed to contaminants believed to havemigrated from groundwater into residentialindoor air. The health consultation evaluates whether exposures exceed a level of health concern.

In April 1997, the site was added to EPA's National Priorities List (NPL) as a result oftrichloroethylene (TCE) detections in several of the city's drinking water supply wells, and later,TCE and tetrachloroethylene (PCE) detections in soil and groundwater west of the wellfield. Thecontamination is believed to have originated from several businesses in the commercial areaupgradient (west) of the wellfield and west of the Palermo neighborhood, near the intersection ofCapitol Boulevard and Trosper Road (Figure 1). Information collected during the RemedialInvestigation (RI) indicate that PCE and TCE are present in two distinct groundwater plumes, whichwere believed to have flowed with the groundwater to the base of the Palermo Bluff located aboveresidences in the Palermo Valley. As the contaminated groundwater surfaced at the base of the Bluff,it is believed to have collected in low areas and crawl spaces underneath residences along Rainier Avenue (Figure 2).

Computer modeling conducted by EPA indicated that TCE and PCE in surface water beneath homescould move into indoor air and pose a health risk to residents. To eliminate this risk, EPAconstructed a subdrain system designed to lower the water table in the vicinity of the affectedresidences. Although construction of the subdrain has been completed, evaluation of its effectivenessis ongoing.

Since EPA relied upon the results of the air model to assess the potential indoor air health hazardposed by PCE and TCE in crawl space water, residential indoor air sampling was not conductedprior to implementation of the subdrain system. Indoor air sampling was conducted only afterimplementation of the subdrain system in order to assess the existence and concentration of PCE and TCE.

Air Sampling Methods and Results

Background: Background is defined here as the concentration of PCE and TCE expected to be present in air without any known contribution from a particular source. Since studies have shown that PCE and TCE are frequently present at low levels in urban indoor and outdoor air, it is useful to compare the expected level to the measured level(s) in order to determine whether the measured level(s) may be higher due to an identified source. Residential indoor air sampling was conducted in late March and late August 2001. Althoughattempts were made to collect samples from 15 homes in the Palermo neighborhood, participationwas limited, and only seven homes were tested. Five of these homes are located in the portion of theneighborhood with the highest groundwater levels and the highest groundwater concentrations ofPCE and TCE. Twenty-four hour samples were collected using flow controllers attached to 6-litersumma canisters. Samples were collected from the crawl space and living space in five of the homes.One home had no crawl space, and access to the living space in another home could not be obtained.As a result, only one air sample was collected from each of these two homes. Background outdoorair samples were collected during both sampling rounds from the backyard of one of the sevenresidences. The sampler was hung from an outdoor lighting fixture positioned approximately head-height.

PCE was detected in the living space of one residence, and in the living space and crawl space ofanother residence. TCE was detected in the living space and crawl space of one residence. NeitherPCE nor TCE were detected above the 1 microgram per cubic meter reporting limit at thebackground locations.

PCE and TCE concentrations were low in the residences where it was detected, and are discussed in more detail below, relative to their potential health impacts.


DISCUSSION

Tetrachloroethylene (PCE)

PCE is a manufactured compound widely used for dry cleaning fabrics and as a metal degreaser. Itis also used as an intermediate in the manufacturing of other products. It is a nonflammable liquid atroom temperature, evaporates easily into the air, and has a sharp, sweet odor. Most people can beginto smell PCE when it is present in the air at or above a level of 100 parts per billion (ppb). Levels ofPCE at both Palermo residences where it was detected were over 300 times below this odor level.

Non-cancer toxicity:

Since the maximum concentration of PCE detected in indoor air was over 100 times lower thanATSDR's non-cancer health comparison value (i.e., 272 micrograms per cubic meter chronicEMEG), exposures to the levels detected are not expected to result in noncarcinogenic health effects.

Cancer toxicity:

The carcinogenicity characterization has a long history. A July 1985 Health Assessment documentfor PCE classified it as a Group C (possible human) carcinogen, but indicated that it would bereevaluated based on new information. An April 1987 addendum to the Health Assessmentdocument proposed that it be classified as a B2 (probable human) carcinogen, and provided arevised inhalation risk estimate. A February 1991 document discussed newer data relative to weight-of-evidence classification. The EPA's Science Advisory Board has determined that these documentsare technically adequate, and offered an opinion that the weight-of-evidence is on C-B2 continuum(possible human carcinogen/probable human carcinogen). Currently, the Agency has not adopted afinal position on the weight-of-evidence classification. The International Agency for Research onCancer (IARC) considers PCE as a Class 2A carcinogen (probably carcinogenic to humans, basedon limited human evidence and sufficient evidence in animals). The U.S. Department of Health andHuman Services determined that it may reasonably be anticipated to be carcinogenic to humans.

Although a number of human studies (primarily epidemiology studies of dry-cleaning workers)suggest the possibility of increased cancer incidences from exposure to PCE, particularly esophagealand bladder cancers, it has not been shown to definitively cause cancer in humans. Other cancerssuspected of being associated with exposures to high levels of PCE (thousands of times higher thanlevels measured in Palermo residences) include intestinal, pancreatic, lung, kidney, skin, colon, andlymphatic/hematopoietic cancer. Following inhalation exposure to PCE, mononuclear cell leukemiawas observed in rats and hepatic tumors were observed in mice. However, because bothmononuclear cell leukemia and hepatic tumors are common in rats and mice, respectively, therelevance of these tumors to humans is not clear.

The concentrations of PCE in indoor air detected in the two Palermo residences were from over300,000 to over 600,000 times lower than the cancer effect levels (CEL) derived in the rodentstudies discussed above. Although the cancer slope factor for PCE has been removed pending thereassessment, the previous slope factor can be used to estimate cancer risk. The estimated increasedchance of developing cancer from chronic exposure to the maximum detected concentration ofPCE in indoor air is insignificant, approximately one additional cancer in a population of tenmillion persons exposed. Some or all of this estimated risk can be attributed to background levels ofPCE commonly found in the indoor air of urban residences (Table 3).

Trichloroethylene (TCE)

TCE is primarily used as a metal degreaser. The primary users of this compound are the automotiveand metals industries. It is also found in some household products, such as typewriter correctionfluid, paint removers, adhesives, and spot removers. Most people can begin to smell TCE in air at orabove 100,000 parts per billion. Levels of PCE in the single Palermo residence where it wasdetected were about 100,000 times below this odor level.

The National Center for Environmental Assessment (NCEA) is currently finishing a revised human health risk assessment on TCE. This assessment will present EPA's most current evaluation of the potential health risks from exposure to TCE. TCE exposure is associated with a number of adverse health effects, including neurotoxicity, immunotoxicity, developmental toxicity, liver toxicity, kidney toxicity, endocrine effects, and several forms of cancer. The mechanistic information suggests some risk factors that may make some populations more sensitive, and that TCE could affect children and adults differently.

Non-cancer toxicity:

Although a chronic-duration inhalation health comparison value (MRL, or minimal risk level) iscurrently not available, ATSDR has derived an intermediate-duration MRL of 537 g/m3 (100 ppb)for inhalation exposure to TCE. The MRL is based on neurological effects on rats observed in a1994 study. An EPA inhalation reference concentration (RfC) of 40 g/m3 has also been derived,and is based on critical effects in the central nervous system, liver, and endocrine system. TCEconcentrations measured in indoor air at the single residence where it was detected were 100 to170 times lower than the MRL, and seven to 13 times lower than the RfC, indicating thatneurological or other non-carcinogenic health effects would not be expected.

Cancer toxicity:

Mechanistic research indicates that TCE-induced carcinogenesis is complex, involving multiplecarcinogenic metabolites acting through multiple modes of action. In 1985, EPA classified TCE as aprobable human carcinogen. Three years later EPA reviewed information suggesting the weight-of-evidence was on a possible human carcinogen - probable human carcinogen continuum. UnderEPA's proposed (1996, 1999) cancer guidelines, TCE can be characterized as "highly likely toproduce cancer in humans." These findings are consistent with those of the International Agency onResearch of Cancer (IARC, 1995) and the National Toxicology Program (NTP, 2000). As a resultof the reassessment, EPA withdrew the inhalation and oral unit risk values.

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.

TCE cancer effects 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 600,000 ppb.The levels of TCE measured in Palermo residential indoor air samples were from 100,000 to600,000 times lower than these CELs.

In order to estimate cancer risk for persons assumed to be chronically exposed to the detected levelsof TCE in indoor air, the previous EPA inhalation slope factor was used. The estimated increasedcancer risk was slight, approximately one additional cancer in a population of one millionpersons exposed over many years. As with PCE, some or all of this estimated risk can be attributedto background levels of TCE commonly found in the indoor air of urban residences (Table 3).

Background Levels of PCE and TCE in Indoor Air:

PCE and TCE concentrations measured in Palermo residential indoor air were at levels consistentwith those often found in indoor urban environments.

The presence of contaminants in ambient and indoor air in urban areas has been well established. Itis also clear that levels of VOCs in indoor air are consistently higher than those found in ambient air.Table 3 and Table 4 below shows the maximum concentrations of PCE and TCE measured atPalermo residences, compared to background indoor and outdoor air concentration ranges, based onvarious U.S. studies.

Based on the small number of Palermo residences where PCE and/or TCE was detected and tested(three out of seven residences tested), it is impossible to definitively ascertain the source of thesecontaminants. Although the contaminated groundwater may be the source, the levels of PCE andTCE detected in Palermo residential indoor air are also similar to those expected in a typical, urban indoor-air environment (i.e., background).

Table 1.

PCE and TCE indoor air concentrations (in micrograms/cubic meter)Palermo Valley residences, Tumwater, Washington
House 1
March 28, 2001

August 22, 2001

Living Space PCE 2.1 (= 0.31 ppb) Living Space PCE 1.8 (= 0.27 ppb)
TCE ND TCE ND
Crawlspace PCE ND Crawlspace PCE ND
TCE ND TCE ND
House 2

March 28, 2001

August 22, 2001

Living Space PCE Not tested Living Space PCE Not tested
TCE Not tested TCE Not tested
Crawlspace PCE ND Crawlspace PCE ND
TCE ND TCE ND
House 3

March 28, 2001

August 22, 2001

Living Space PCE ND Living Space PCE Not tested
TCE ND TCE Not tested
Crawlspace PCE Not tested (no crawlspace) Crawlspace PCE Not tested
TCE Not tested (no crawlspace) TCE Not tested
House 4

March 28, 2001

August 22, 2001

Living Space PCE ND Living Space PCE ND
TCE 3.1 (= 0.58 ppb) TCE 2.2 (= 0.41 ppb)
Crawlspace PCE ND Crawlspace PCE ND
TCE 5.6 (= 1 ppb) TCE 4.6 (= 0.86 ppb)
House 5

March 28, 2001

August 22, 2001

Living Space PCE ND Living Space PCE ND
TCE ND TCE ND
Crawlspace PCE ND Crawlspace PCE ND
TCE ND TCE ND
House 6

March 28, 2001

August 22, 2001

Living Space PCE ND Living Space PCE ND
TCE ND TCE ND
Crawlspace PCE ND Crawlspace PCE ND
TCE ND TCE ND
House 7

March 28, 2001

August 22, 2001

Living Space PCE Not tested Living Space PCE 1.8 (= 0.27 ppb)
TCE Not tested TCE ND
Crawlspace PCE Not tested Crawlspace PCE 2.1 (= 0.31 ppb)
TCE Not tested TCE ND
Background (outdoor) air sampling results

March 28, 2001: 5003 Rainier Ave. (ND) August 22, 2001: 5003 Rainier Ave. (ND)


Table 2.

PCE and TCE health comparison values(in micrograms per cubic meter)
Chemical Maximum indoor air concentration Non cancer health comparison value Cancer comparison values Cancer risk at maximum concentration
PCE 2.1 (living space sample) 272 (chronic EMEG/MRL) 4.38 (MTCA B, CLARC II update)
3.1 (EPA Region 3)
1 x 10-7
TCE 5.6 (crawlspace sample)
3.1 (living space sample)
537 (Intermediate EMEG/MRL)
40 (Inhalation RfC)
1.46 (MTCA B, CLARC II update)
1.0 (EPA Region 3)
1 x 10-6
7 x 10-7

EMEG = ATSDR Environmental media evaluation guide
MRL = ATSDR Minimal risk level
MTCA = Washington State Model Toxics Control Act
CLARC = Department of Ecology Cleanup Levels and Risk Calculations
Inhalation RfC = EPA Inhalation Reference Concentration


Table 3.

Contaminants of concern detected in indoor air, Palermo residences, Tumwater, Washington(in micrograms per cubic meter)
Contaminant Maximum Detected Concentration Indoor Air Background Level Ranges
(based on various studies)
Source of Indoor Air Background Level Ranges
Tetrachloroethylene (PCE) 2.1 0.4 - 9 Shah/Pellizzari
Trichloroethylene (TCE) 5.6 0.075 - 7 Shah/Pellizzari


Table 4.

Background levels of PCE and TCE measured in outdoor air, Palermo neighborhood, Tumwater, Washington(in micrograms per cubic meter)
Contaminant Palermo Background (Outdoor) Air Concentration Outdoor Air
Background Level Ranges
(based on various studies)
Source of National Outdoor Air Background Level Ranges
Tetrachloroethylene (PCE) Not detected 0.31 - 0.66 Shah/Wallace
Trichloroethylene (TCE) Not detected 0.2 - 0.7 Shah/Wallace


CHILD HEALTH INITIATIVE

ATSDR's Child Health Initiative recognizes that the unique vulnerabilities of infants and childrendeserve special emphasis with regard to exposures to environmental contaminants. Infants, youngchildren, and the unborn may be at greater risk than adults from exposure to particularcontaminants. Exposure during key periods of growth and development may lead to malformation oforgans (teratogenesis), disruption of function, and even premature death. In certain instances,maternal exposure, via the placenta, could adversely effect the fetus. After birth, children mayreceive greater exposures to environmental contaminants than adults. Children are often more likelyto be exposed to contaminants from playing outdoors, ingesting food that has come into contact withhazardous substances, or breathing soil and dust. Pound-for-pound of body weight, children drinkmore water, eat more food, and breathe more air than adults. For example, in the United States,children in the first 6 months of life drink seven times as much water per pound as the average adult.The implication for environmental health is that, by virtue of children's lower body weight, giventhe same exposures, they can receive significantly higher relative contaminant doses than adults.

Reproductive Health Effects

Adverse reproductive health effects in women have been reported to be associated with occupationalexposures to PCE in the dry cleaning industry. These effects included menstrual disorders andspontaneous abortions. However, limitations of these studies precluded a definitive associationbetween PCE exposure and these health effects. Levels of PCE and TCE detected in indoor airwere well below levels at which reproductive effects were observed in the relevant animalstudies. As a result, adverse reproductive health effects would not be expected.

Developmental Health Effects

The developing fetus, children, and especially the developing nervous system may be particularlysusceptible to the toxic effects of PCE. Animal studies suggest that PCE can cross the placenta andthat TCA, a metabolite of both PCE and TCE, concentrates in the fetus. Unmetabolized PCE hasbeen excreted in breast milk, and in one health study, was detected in an exposed infant with liverdamage. Rats that were given oral doses of PCE when they were very young, while their brains werestill developing, were hyperactive when they became adults. It is not known whether PCE may havesimilar effects on the developing brain in human babies.

In Woburn, Massachusetts, studies of residents exposed to drinking water contaminated withsolvents, including PCE, suggest the possible association of exposure to PCE and eye/ear anomaliesand central nervous system/chromosomal/oral cleft anomalies. However, it is unclear whether otherconfounding factors might have influenced these health outcomes.

Under certain conditions of exposure, TCE is also believed to affect the developing fetus. Childrenhave also been identified as a potentially susceptible population. The levels of PCE and TCEdetected in indoor air were well below levels which caused developmental health effects in these studies. As a result, adverse developmental health effects would not be expected.


CONCLUSIONS

1) PCE was detected at low levels in indoor air at two of the seven residences tested, while TCEwas detected at low levels in indoor air at one of the seven residences tested.

2) The levels of PCE and TCE detected in residential indoor air do not pose a non-cancer healthhazard. A slight increased cancer risk was estimated for residents assumed to be exposed to themaximum detected level of TCE continuously over many years. However, this risk is similar to thatexpected to result from background exposure to TCE and PCE. Exposures to the detected levels ofPCE and TCE in indoor air pose no apparent public health hazard.

  • PCE and TCE levels detected in indoor air were well below levels that would result inadverse reproductive or developmental health effects.

3) Studies have shown that VOCs (such as PCE and TCE) are usually present at low levels inoutdoor and indoor air in urban areas. Outdoor sources include automobile exhaust and industrialemissions, while indoor air contaminants often come from household cleaners, paints, carpeting, andbuilding materials.As a result, background levels of VOCs in indoor and outdoor air are a source ofexposure for residents living in urban environments. Health risks associated with backgroundexposure can be similar to or higher than risks from localized hazardous waste releases to theenvironment. Based on the limited number of Palermo residences tested, it is not clear whether thesource of the indoor air detections is the contaminated groundwater, or other unrelated background source(s).


RECOMMENDATIONS/ACTION PLAN

1) Copies of this health consultation will be provided to residents whose homes were tested, EPA,and Ecology. Additional copies will be available upon request.

2) Follow up with residents' whose homes were tested should be conducted by EPA and DOH toexplain the results of the indoor air analysis.

3) DOH should be notified if groundwater and/or surface water chemical concentrations increase,posing an increased potential health hazard to residences at the base of the Palermo bluff..


PREPARER OF REPORT

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


Designated Reviewer

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


Technical Project Officer

Debra Gable
Technical Project Officer
SPS, SSAB, DHAC
ATSDR


REFERENCES

  1. United States Environmental Protection Agency. Status Report, February - April 2001,Subdrain System and Treatment Lagoon, Palermo Wellfield Superfund Site, Tumwater,Washington. May 2001.

  2. United States Environmental Protection Agency. Draft Final Operation and Maintenance Plan Subdrain System and Treatment Lagoon, Palermo Wellfield Superfund Site, Tumwater,Washington. December 2000.

  3. Performance Analytical, Inc. Results of residential indoor air analysis. September 12, 2001.

  4. United States Environmental Protection Agency. Fact sheet on Release of External Review Draft of Trichloroethylene Health Risk Assessment. August 16, 2001.

  5. Environmental Quality Management, Inc. Memorandum: Indoor air modeling for the Palermo Wellfield Superfund Site. April 14, 1999.

  6. United States Environmental Protection Agency. Final Record of Decision: Palermo Wellfield Superfund Site, City of Tumwater, Thurston County, Washington. October 1999.

  7. United States Environmental Protection Agency. Fact Sheet: Palermo Wellfield, Tumwater, Washington. February 2001.

  8. United States Environmental Protection Agency. Fact Sheet: Palermo Wellfield, Tumwater, Washington. November 1999.

  9. United States Environmental Protection Agency. Fact Sheet: Palermo Wellfield, Tumwater, Washington. June 1999.

  10. Agency for Toxic Substances and Disease Registry. Toxicological Profile forTetrachloroethylene. September 1997.

  11. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Trichloroethylene. September 1997.

  12. Shah JJ. and Sing HB. Distribution of volatile organic chemicals in outdoor and indoor air. Environmental Sci. Technol.. Vol. 22, No. 12, 1988.

  13. Wallace LA and Pellizzari. Total Exposure Methodology (TEAM) Study: Personal Exposures, indoor-outdoor relationships and breath levels of volatile organic compounds in New Jersey.

  14. Pellizzari, E.D. and Breen J.J. Comparison of Indoor and Outdoor Residential Levels of Volatile Organic Chemicals in Five U.S. Geographical Areas. Environment International, Vol. 12, pp 619-623, 1986.

  15. National Center for Environmental Assessment, U.S. Environmental Protection Agency. Risk Assessment Issue Paper for: Carcinogenicity Information for Tetrachloroethylene. October 25, 2001.

  16. Washington State Department of Ecology. Model Toxics Control Act Cleanup Regulation. Chapter 173-340 WAC.

FIGURES

Project Area Location Map
Figure 1. Project Area Location Map

Project Area Plan View
Figure 2. Project Area Plan View


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.

Richard Gillig
Branch Chief
SSAB, DHAC
ATSDR



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