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HEALTH CONSULTATION

LOCKWOOD SOLVENTS
BILLINGS, YELLOWSTONE COUNTY, MONTANA


BACKGROUND AND STATEMENT OF ISSUES

The Montana Department of Environmental Quality (MDEQ) requested the Agency for Toxic Substances and Disease Registry (ATSDR) review the results of well water samples collected at Lockwood Solvent site in Billings, Montana. The purpose of the review was to determine (1) if chlorinated solvents in well water represent a public health concern for skin contact and breathing during indoor (bathing) and outdoor water use, and (2) if contaminant levels in well water represent a public health concern from chlorinated solvent evaporation and migration into homes via the soil gas pathway. Additionally, ATSDR was requested to determine if the levels of groundwater contaminants present a health hazard to workers installing and repairing water mains.

The Lockwood Solvent site is located in the eastern portion of Billings, Montana. The site is bordered by Rosebud Lane to the south, Klenck Lane to the east and the Yellowstone River to the north and west.

The MDEQ collected well water samples from approximately 20 homes and 15 businesses during 1998 and 1999. The samples were analyzed for volatile organic compounds (VOCs). The results of the water sampling were provided to ATSDR in a map prepared by MDEQ contractor (Pioneer Technical Services) dated February 17, 1999.

Results of the environmental sampling indicated that tetrachloroethene, TCE, vinyl chloride, and cis-1,2 dichloroethene are the four contaminants of concern. The maximum concentrations of these contaminants detected in groundwater are: tetrachloroethene (1.9 milligrams per liter (mg/L)), vinyl chloride (0.190 mg/L), TCE 0.150 (mg/L), and cis-1,2 dichloroethene (0.590 mg/L). These contaminant levels were detected in a well at one home on Lomond Lane.

Residents of this home are provided an alternate source of water for drinking and bathing. Residents of eight additional homes in the Lockwood community are being provided bottled drinking water.

The maximum concentrations of the contaminants of concern found at homes without alternate water supplies for bathing are: tetrachloroethene ( 0.670 mg/L), vinyl chloride (0.160 mg/L), TCE (0.130 mg/L), and cis-dichloroethene (0.470 mg/L).


DISCUSSION - SHOWERING

When showering in chlorinated hydrocarbon-contaminated water, a resident may be exposed from (1) breathing the portion of the contaminant that is released into the air and (2) absorbing the contaminant through the skin. A resident could inhale the vapor while showering and while standing in the bathroom immediately after showering.

Studies in humans have demonstrated that the dermal absorption dose of a chlorinated volatile organic compound (chloroform) is comparable to the shower inhalation dose [1].

ATSDR made the following assumptions to estimate tetrachloroethene exposure to adults and children who are showering with tetrachloroethene-contaminated water:

(1) a resident would take a 10 minute shower once per day, and
(2) a resident spends an additional 15 minutes in the bathroom after showering.
(3) the rate of skin absorption of PCE is similar to rate for chloroform absorption

The maximum concentration of tetrachloroethene in the bathroom can be estimated by the following mathematical formula [2]:

C sub a equals C sub w times k times F times t divided by V

where:

Ca = air concentration in milligrams per liter (mg/L)
Cw= tetrachloroethene concentration in tap water in milligrams per liter (0.67 mg/L)
k = volatile mass transfer coefficient in liter per minute (conservatively assumed to be .9)
F= flow rate in liters per minute (L/min) (assumed to be 8 liters per minute)
t = shower time in minutes (10 minute shower)
V = bathroom volume in liters (assumed to be 10,000 liters) (This is approximately the size of a small bathroom.)

If the concentration of tetrachloroethene in the shower water is 0.67 mg/liter, the maximum concentration of tetrachloroethene in the bathroom air is estimated to be 4.8 milligrams per cubic meter (mg/m3) or 0.71 parts per million (ppm) (6.78 mg/m3 = 1 ppm).

Assuming an adult breathes 1.0 cubic meter of air per hour and the water concentration is 0.67 mg/liter, the estimated exposure during showering and subsequent bathroom use are as follows:

shower inhalation dose = (4.8 mg/m3) x (1.0 m3/hr) x (10/60 hr) = 0.8 mg

sink inhalation dose = (4.8 mg/m3) x (1.0 m3/hr) x (15/60 hr) = 1.2 mg

shower dermal dose = shower inhalation dose = 0.8 mg

total dose = showerinh + sinkinh + showerder = 2.8 mg/day

This model estimates a worst case air concentrations since it does not take into account dilution from ventilation in the bathroom, and it assumes exposure at a maximum air concentration throughout duration of the bathroom use. The tetrachloroethene concentration will gradually increase to a maximum at the end of the shower then gradually decrease once the shower is turned off.

ATSDR has established an acute (short-term) inhalation Minimal Risk Level (MRL) of 0.2 ppm and a chronic (long-term) inhalation MRL of 0.04 ppm for tetrachloroethene. (ATSDR's methods for reviewing environmental data are summarized in Appendix A.) The lowest observed adverse effect level (LOAEL) for acute inhalation exposure to tetrachloroethene is 50 ppm [3]. This is also the basis for the acute MRL. Humans exposed to 50 ppm for 4 hours were observed to have neurological effects (i.e. slight loss of visual contrast). This effect was not observed at 10 ppm. At water concentration of 0.67 mg/liter, the predicted maximum air concentration of 0.71 ppm during showering is approximately 70-fold less than the LOAEL.

The 0.04 ppm MRL (chronic) is based on increased reaction times by dry cleaning workers exposed to 15 ppm tetrachloroethene for ten years. This MRL includes an uncertainty factor of 100. Exposure to tetrachloroethene at the 0.04 ppm (0.271 mg/m3)- MRL (chronic) is equivalent to a 6.5 mg per day dose for an adult breathing one cubic meter of air per hour for 24 hours. The estimated total daily dose (inhalation and dermal) from shower-bathroom use (2.8 mg/day) is approximately one third of the inhalation dose of exposure at the chronic MRL when the shower water contains 0.67 mg/L.

The predicted maximum concentration of vinyl chloride during showering is 0.45 ppm, based on a groundwater concentration of 0.16 mg/L. ATSDR MRL for inhalation of vinyl chloride is 0.5 ppm (acute) and 0.03 ppm (intermediate)[4]. The acute MRL is based on a no observed adverse effect level (NOAEL) of 50 ppm. Laboratory animals were exposed to 50 ppm of vinyl chloride for seven hours a day for a 10-day period without adverse effects to the adult animals or their fetuses. The LOAEL for intermediate exposure to vinyl chloride is 10 ppm. Laboratory animals exposed to 10 ppm of vinyl chloride for six months were observed to have increased liver weights. The MRL is based on this LOAEL and includes an uncertainty factor of 300. The predicted maximum air concentration is approximately 20-fold less than the LOAEL. ATSDR has not established a chronic MRL for vinyl chloride for inhalation exposure. Vinyl chloride is recognized as a cancer causing agent [4]. Studies have demonstrated that workers who have breathed vinyl chloride over long periods (years) have an increased risk of developing liver cancer. As a result, breathing low levels of vinyl chloride vapors over long periods may increase the risk of developing liver cancer.

The predicted maximum concentration of TCE during showering is 0.174 ppm, based on a groundwater concentration of 0.13 mg/L of TCE. ATSDR has established an acute inhalation MRL of 2 ppm and intermediate inhalation MRL of 0.1 ppm for TCE [5]. The LOAEL for inhalation intermediate exposure to TCE is 50 ppm. Laboratory animals exposed to 50 ppm of TCE for a six week period exhibited decreased wakefulness during exposure. The intermediate MRL is based on this study and includes an uncertainty factor of 300. The predicted maximum concentration of TCE (0.174 ppm) is above the intermediate MRL (0.1 ppm). However, ATSDR does not anticipate adverse health effects to occur because of the short duration of exposure at this level (less than one hour each day.) ATSDR has not established a chronic MRL for TCE for inhalation exposure.

The predicted air concentration during showering is 0.85 ppm based on a groundwater concentration of 0.47 milligrams per liter of cis-dichloroethene. ATSDR has not established an MRL for cis-dichloroethene because of a lack of data [6]. ATSDR has established an intermediate MRL for trans-dichloroethene of 0.2 ppm. This MRL is based on liver damage to laboratory animals that were exposed to 200 ppm of trans-dichloroethene for a sixteen week period and includes an uncertainty factor of 1,000.


OUTDOOR WATER USE

Breathing zone concentration of tetrachloroethene and other contaminants of concern during outdoor water use (e.g. sprinkler use) will be less than maximum concentrations predicted during showering because of dispersion, lower average outdoor temperature, and less atomization of water droplets. The amount of dermal exposure during outdoor use depends on the amount of body surface area in contact with the groundwater and duration of contact with the water. Dermal exposure from outdoor water use is likely to be similar to, or less, than dermal exposure resulting from a showering if contact time is 10 minutes per day or less.


VAPOR INTRUSION

ATSDR used the Johnson and Ettinger Model (tier-1) for Subsurface Vapor Intrusion to evaluate the vapor intrusion pathway [7]. The screening model was run using the following inputs: maximum contaminant concentrations, depth below bottom of home (18 inches), depth below grade to water table (72 inches), average soil/groundwater temperature (48 F), and soil type (sand). Results of the initial modeling suggests that, based on worst case conditions, chlorinated solvent vapors could enter homes through crawl spaces and result in occupant exposure at low levels. Because this is an initial screening model, the results indicated the need for further investigation of this pathway.


OCCUPATIONAL EXPOSURE WATER COMPANY WORKERS

The American Conference of Governmental Industrial Hygienist's (ACGIH) Threshold Limit Value TLVs® for three of the contaminants of concern are the following: tetrachloroethene (25 ppm); vinyl chloride (5 ppm), and TCE (50 ppm)[8]. ACGIH has not established a cis-dichloroethene. These exposure guidance values are based on an eight-hour time weighted average. Workplace concentrations of contaminants are unlikely to approach these values during normal water company operations, based on the maximum concentrations detected in groundwater. Workers may avoid dermal exposure to chlorinated solvent-contaminated groundwater by using the appropriate chemical resistant gloves (e.g., nitrile butyl rubber gloves).


CHILD HEALTH INITIATIVE

ATSDR's Child Health Initiative recognizes that the unique vulnerabilities of infants and children demand special emphasis in communities concerned about contamination of air and water. Children are at greater risk than adults from certain kinds of exposures to hazardous substances released into their environment. Because children are smaller than adults, exposure may result in higher dose per body weight. Also, children's developing body systems can sustain damage if toxic exposures occur during critical growth stages. ATSDR has taken these factors into account in the development of this health consultation.


CONCLUSIONS

The predicted levels of chlorinated solvent vapors, including vinyl chloride, during showering and bathroom use represent no apparent public health hazard to the Lockwood community, during short-term or intermediate term exposure (i.e., less than one year).

The low levels of chlorinated solvent vapors resulting from the use of contaminated well water for showering and bathing may present a public health hazard over long-term periods (several years) of exposure.

Results of the initial screening modeling suggest that low levels of chlorinated solvent vapor, including vinyl chloride, could possibly enter homes through home foundations by vapor intrusion. Breathing low levels of vinyl chloride vapor from vapor intrusion over long-term periods would represent a public health hazard. However, additional sampling is necessary to determine if this exposure pathway exists.

The anticipated levels of inhalation and dermal exposure resulting from outdoor use of contaminated well water by residents and workers of the Lockwood Water Users Association represent no apparent health hazard.


RECOMMENDATIONS

The recommendations listed below identify actions that ATSDR believes are prudent to reduce any potential health hazards that might be associated with long-term low level exposure to chlorinated solvents during showering and bathing.

The Environmental Protection Agency and the Montana Department of Environmental Quality should:

  1. develop and implement an alternate source of water supply for the Lockwood community to prevent long-term exposure (e.g, longer than one year) to chlorinated solvents during showering and bathing.

  2. collect soil gas samples to investigate the vapor intrusion pathway into homes where the groundwater contains greater than 0.005 mg/L of vinyl chloride. (Sampling should include active air samples for contaminants of concern.)

PREPARERS OF REPORT

Peter J. Kowalski, CIH
Environmental Health Scientist
Exposure Investigations and Consultations Branch
Division of Health Assessment and Consultation


Reviewed by

Susan Moore
Chief, Consultations Section
Exposure Investigations and Consultations Branch
Division of Health Assessment and Consultation

Greg Zarus
Atmospheric Scientist
Exposure Investigations and Consultations Branch
Division of Health Assessment and Consultation


REFERENCES

  1. Wan K. Jo, Clifford P. Weisel, and Paul J. Lioy; Routes of Chloroform Exposure and Body Burden from Showering with Chlorinated Tap Water; Risk Analysis.10(4) 575-580 (1990).

  2. Andelman, JB; Total Exposure to Volatile Organic Compounds in Potable Water. In Significance and Treatment of Volatile Organic Compounds in Water Supplies. Lewis Publishers. Chelsea, MI. 485-504. (1990).

  3. Agency of Toxic Substances and Disease Registry. Toxicological Profile for Tetrachloroethene. Atlanta: U.S. Department of Health and Human Services. Public Health Service. 1996.

  4. Agency of Toxic Substances and Disease Registry. Toxicological Profile for Vinyl Chloride. Atlanta: U.S. Department of Health and Human Services. Public Health Service. 1997.

  5. Agency of Toxic Substances and Disease Registry. Toxicological Profile for Trichloroethylene. Atlanta: U.S. Department of Health and Human Services. Public Health Service. 1996.

  6. Agency of Toxic Substances and Disease Registry. Toxicological Profile for 1,2-Dichloroethene. Atlanta: U.S. Department of Health and Human Services. Public Health Service. 1996.

  7. User's Guide for the Johnson and Ettinger (1991) Model for Subsurface Vapor Intrusion into Buildings. Washington: U.S. Environmental Protection Agency.1997.

  8. 1998 TLVs® and BEIs®. Cincinnati: American Conference of Governmental Industrial Hygienists (ACGIH). 1998.

APPENDIX A: HEALTH CONSULTATION, LOCKWOOD SOLVENTS SITE, DECEMBER 9, 1999

ATSDR's approach to evaluating environmental data is to examine the pathways by which the public might be exposed. ATSDR looks for five elements of a completed exposure pathway. These elements are (1) a release of a chemical; (2) the mechanisms and media of transport (i.e., how the chemical moves and whether it moves through air, soil, or water); (3) the point of exposure (where actual or potential human contact with the chemical may occur); (4) the route of exposure (such as eating, drinking, inhaling, etc.); and (5) the receptor population (details about the people who may be exposed). If these elements are not present (or it is not reasonably possible for all of the pathway elements to be complete), ATSDR notes that the pathway is not completed.

A completed exposure pathway is necessary for a health hazard to exist. The implications of exposure are evaluated once a completed pathway has been established. The health effects from breathing air contaminants depends on the type and amount of the contaminants, the duration of exposure, and health of the exposure (receptor) population.

ATSDR uses media-specific comparison values (e.g., amount of chemical in air) to screen for further evaluation. ATSDR evaluated the type and amount of contaminants measured in the air samples and compared them to ATSDR Minimal Risk Levels (MRLs) and American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Values (TLVs®).

MRLs are considered to be safe levels of exposure. They are developed using conservative exposure assumptions and uncertainty factors and are generally much lower than exposure concentrations noted to cause harmful health effects. MRLs are set below levels that, based on current information, might cause adverse health effects in the people most sensitive to such substance-induced effects. MRLs are established for acute (1-14 days), intermediate (15-364 days), and chronic (365 days and longer) exposure durations, and for the oral and inhalation routes of exposure. If the air contaminant levels are below the MRL, then the exposure is unlikely to be a public health concern. Due to conservative assumptions it should not be concluded that a concentration greater than the comparison value will necessarily lead to harmful health effects in healthy populations.

The ACGIH (ACGIH) Threshold Limits Values (TLVs®) represent the level of air contaminants that nearly all workers can be repeatedly exposed to without adverse health effects [3]. TLVs® are guidance values for occupational exposures that based on eight-hour time weighted averages.



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