(MTBE Contamination in Residential Wells)
MIKE'S FANCY SERVICE STATION SITE
EARL TOWNSHIP, BERKS COUNTY, PENNSYLVANIA
At the request of the United States Environmental Protection Agency (USEPA), the Pennsylvania Department of Health (PADOH), working under a cooperative agreement with the Agency for Toxic Substances and Disease Registry (ATSDR), prepared this health consultation (HC) to determine if residents living near the Mike's Fancy Service Station Site (the site) are exposed to methyl t-butyl ether (MTBE) in their private well water during showering at levels that would harm their health.
Exposure to MTBE represents no apparent health hazard for the residents living along Garber Road, Maple Avenue, and Sunrise Lane who used water from their private residential wells for showering. The levels of MTBE in their well water were low and exposure to them during showering (and ingestion) did not threaten the health of families using their wells.
Exposure to MTBE represents an indeterminate health hazard for residents living in a single home along Sunrise Lane whose private well water was not sampled because of denial of access by the owner. The residential well for this home is potentially impacted by site-related contaminated groundwater. It is not know whether residents in this home have installed an inline filtration unit, are using bottled water, or have taken any other measure to protect their health from potential exposure to MTBE. PADOH and ATSDR recommend that, if possible, water from this private well be sampled for MTBE.
The interpretation, conclusions, and recommendations regarding the Mike's Fancy Service Station Site are site-specific and do not necessarily apply to any other site.
Mike's Fancy Service Station Site (the site) lies along Pennsylvania Route 562 in the town of Worman in Earl Township, Berks County, Pennsylvania (Figures 1,2). The approximately 1-acre site is in a rural area which is zoned for agricultural and residential use. Approximately 150 people currently live within a one-quarter mile radius of the site. The distance from the nearest off-site residence to the site is about 150 feet.
Groundwater at the site is contaminated with MTBE. MTBE has migrated off the site property through groundwater into nearby residential wells (RWs) . Approximately 30 people are served by private RWs along Garber Road, Maple Avenue, and Sunrise Lane that are contaminated with MTBE (Figure 2). Most of the residents living in homes in this area with MTBE in their well water had in-line water filtration units at the time of its discovery. The filtration units were historically installed by USEPA to prevent exposure to TCE that originated at CryoChem, Incorporated (Inc.), another nearby site . USEPA and PADEP have the mutual objective of ensuring that the homes near the CryoChem Site and Mike's Fancy Service Station Site have a safe and potable water supply. Filters were installed in the homes impacted by the CryoChem, Inc. Site and are monitored and maintained by Vitillo, Inc. and Culligan for C.S. Garber and Sons, Incorporated .
During June and July 2001, HydroScience Incorporated (HydroScience), a contractor for the owner of Mike's Fancy Service Station (the responsible party for the site), sampled well water from thirty-one (31) residential wells near the site. Water from ten (10) residential wells (RWs- 72, 88, 89, 101-105, 107, and 116) southeast of the site along Garber Road, Maple Avenue, and Sunrise Lane was found to be contaminated with MTBE . Two (2) of the wells (RW-104 and RW-116) did not have inline filters and the residents were not using bottled water at the time of the June-July 2001 sampling. Water from four (4) other wells (RWs-88, 89, 101, and 102) was found to contain MTBE at a post filter sampling point. MTBE was detected in the remaining four (4) wells (RWs 72, 103-105) at pre-filter sampling points and was not reaching consumers.
Exposure to MTBE in the well water through drinking or cooking was not a health issue for residents in all six of the homes where it reached consumers because the levels were below ATSDR's health based guidelines for ingestion . These guidelines do not take into account aesthetics such as odor which can occur at the levels found in some of the residential wells. The primary health issue is whether residents using water from these wells (RWs-88, 89, 101, 102, 104 and 116) were exposed to MTBE through inhalation during showering at levels that could harm their health.
The concentrations of MTBE detected in well water at post filter sampling points and in well water for homes without filters ranged from 27 micrograms per liter (µg/L) to 124 µg/L. The maximum concentration of MTBE (124 µg/L) that residents were exposed to through inhalation was detected along Maple Avenue in RW-101. USEPA requested PADOH to evaluate these sampling results and determine the public health significance of families being exposed to MTBE in air during showering . This health consultation (HC) responds to USEPA's request.
On December 4, 2001, Robert M. Stroman, PADOH health assessor, conducted a site visit with representatives from PADEP and USEPA to determine the location of the homes sampled in June and July 2001. During this site visit, we met with the owner of Mike's Fancy Service Station and observed the area where MTBE is known to have contaminated the groundwater. We also determined that there is one (1) home (RW-120) near this area along Sunrise Lane that had a private well that could possibly be contaminated with MTBE that was not sampled.
On February 26, 2002, Robert M. Stroman and Andrew Fetterman, HydroScience, met with residents along Garber Road, Maple Avenue, and Sunrise Lane where MTBE was detected in their private wells. Stroman discussed with residents possible health implications of inhalation exposure to MTBE in bathroom air. Fetterman discussed HydroScience's future plans for site characterization and answered residents' questions.
MTBE is a volatile organic compound that tends to vaporize out of warm water used for showering into air. MTBE exposure during showering can be a health concern because it can be absorbed into the body following inhalation of the contaminated air. Exposure to MTBE through ingestion is not a concern because the families evaluated in this HC currently use bottled water for drinking and cooking. In this section, we evaluate the public health significance of residential exposure to MTBE through inhalation of the volatilized water contaminant during showering. Assumptions used in our evaluation are reported in Appendix A.
As a result of our evaluation, we calculated (using the formula in Appendix A) that showering for 10 minutes with water containing 124 µg/L of MTBE would result in an air concentration of 412 parts per billion (ppb) or 1485 micrograms per cubic meter (µg/m3). ATSDR's acute Minimal Risk Level (MRL) for MTBE in air is 2000 ppb (~7211 µg/m3) . Our calculated concentration of MTBE in the bathroom air is well below ATSDR's acute MRL for MTBE, therefore, no acute health risk is expected.
To evaluate the potential for adverse health effects associated with intermediate and chronic exposures, we express the calculated acute exposure (412 ppb or 1485 µg/m3) as a time weighted average (TWA). The TWA is the concentration of MTBE that the resident would have to be exposed to over a 24 hour period of time that would equate to the amount the person is exposed to during a 10 minute shower. The TWA of MTBE in air is 2.86 ppb or 10.31 µg/m3. This concentration (TWA) of MTBE (2.86 ppb or 10.31 µg/m3) in the bathroom air is well below ATSDR's intermediate and chronic MRLs of 700 ppb or ~2524 µg/m3.
These predicted levels of exposure to MTBE are (1) below ATSDR's health-based guidelines (acute, chronic, and intermediate MRLs), (2) do not threaten the health of the residents using their well water for showering, and (3) represent no apparent health hazard. However, exposure to contaminated bathroom air through inhalation may be aesthetically unpleasing due to odor.
Although the concentrations of these contaminants presently represent no apparent health hazard to the residents using their well water for showering, we cannot be certain that the levels will not increase in the future. If future contaminant levels exceed health-based guidelines or if the groundwater contaminant plume is determined to extend beyond these wells (at levels of health concern) then further evaluation will be needed.
The extent of the groundwater contamination plume has not yet been fully determined and there is an additional well near the site along Sunrise Lane that has not been sampled that might contain MTBE at levels of health concern. HydroScience was denied access to this residence when they requested permission to sample its well water. We do not know if the residents in this home are currently using bottled water or an in-line filtration unit. The absence of this information along with the lack of sampling results for this private well represents a data gap and inhibits our ability to assure that the public health is protected.
PADOH and ATSDR recognize that the unique vulnerabilities of infants and children demand special emphasis in communities faced with contamination of environmental media. As part of ATSDR's Child Health Initiative, ATSDR public health consultations indicate whether site-related exposures are of particular concern for children.
In general, children appear to be more sensitive to the effects of contaminants, presumably because of a higher body burden. However, there is no evidence that the pharmacokinetics (absorption, distribution, metabolism, and excretion) of MTBE differ in children .
PADOH and ATSDR conclude the following:
- Past exposure to MTBE in air during showering at the maximum level evaluated in this HC represents no apparent health hazard for residents living in homes along Garber Road and Maple Avenue that were evaluated in this HC. The levels in the air were low and would not threaten the families' health.
- There is no current threat to the health of the residents who live in homes along Garber Road, Maple Avenue, and Sunrise Lane that are known to be affected because new or rebedded filtration units have been installed in all of these homes and current exposure to MTBE should not exist.
- Further monitoring of water (after filters) and maintenance of the filtration systems is necessary to confirm that MTBE at levels of health concern do not reach the residents potable water supply in the future as the result of filtration unit breakthrough following saturation.
- Potential current exposure to MTBE in one unsampled private well near the site along Sunrise Lane represents an indeterminate public health hazard due to lack of data.
- Further investigation is necessary to determine whether MTBE is present at a level of health concern in an unsampled residential well along Sunrise Lane and if residents are exposed to this contaminant.
- Discuss the public health implications of past exposure to MTBE with residents exposed to this contaminant in their private wells.
- Fully characterize the site (with special emphasis on defining the groundwater contamination plume). This will provide PADOH information to determine if MTBE is present at a level of health concern in a private residential well along Sunrise Lane that was not sampled, or, with regard to the wells evaluated in this HC, whether this contaminant becomes present in the future at levels of health concern.
- Evaluate future sampling results and prepare a health consultation that addresses the public health significance of the data. PADOH will implement this recommendation following receipt of sampling results.
- PADOH will meet with affected residents identified in this HC and discuss the public health significance of their past exposure to MTBE-contaminated well water. PADOH will continue to be available to answer residents' health questions as more information becomes available.
- PADEP and HydroScience conducted a public meeting in Earl Township on November 29, 2001 and provided residents with information on HydroScience's activities at the site .
- HydroScience will attempt to fully define the groundwater contamination plume to determine if MTBE is present in the private residential well along Sunrise Lane that was not previously sampled because of denial of access by the owner .
- HydroScience will monitor in-line filtration units along Garber Road, Maple Avenue, and Sunrise Lane at appropriate time intervals to assure residents do not become exposed to MTBE at a levels of health concern at some time in the future .
- PADOH will evaluate future sampling results and prepare a health consultation that addresses the public health significance of the data.
- HydroScience provided bottled water to residents known to have MTBE in their private well during June and July 2001 .
- HydroScience installed new inline carbon filtration units in RW-104 and RW-116 and rebedded existing filters in all of the other RWs where MTBE was detected in the well water to prevent future exposure to MTBE. Installation of the two (2) new units occurred in November 2001 and rebedding of the existing filters began in December 2001 and was completed in January 2002 .
- HydroScience is currently developing a plan to retard the movement of the contaminated groundwater toward residential wells that includes extraction of the contaminant in the water prior to discharge. It will be the duty of the responsible party to implement this plan .
- Data/documentation package from F. William Noll, Pennsylvania Department of Environmental Protection (PADEP) to Robert M. Stroman, PADOH, December 2001.
- Certified Letter from Alexis K. Alexander, Remedial Project Manager, USEPA to Gregory Bowman, PADEP, January 17, 2002.
- Consultation between Andrew Fetterman, Staff Geologist, HydroScience and Robert M. Stroman, PADOH, February 2002.
- Agency for Toxic Substances and Disease Registry (ATSDR), Soil/Water/Air Comparison Values and Health Guideline Comparison Values, 06/30/01.
- Consultation between Alexis K. Alexander, Remedial Project Manager Andrew, USEPA and Robert M. Stroman, PADOH, December 2001.
- Agency for Toxic Substances and Disease Registry (ATSDR), Toxicological Profile for Methyl tert-Butyl Ether, August 1996.
- Consultation between F. William Noll, Pennsylvania Department of Environmental Protection (PADEP) and Robert M. Stroman, PADOH, January 2002.
Robert M. Stroman, B.S., Pharm.
Pennsylvania Department of Health
This Health Consultation for the Mike's Fancy Service Station Site has been prepared by the Pennsylvania Department of Health under cooperative agreement with the Agency for Toxic Substances and Disease Registry (ATSDR). It is in accordance with approved methodology and procedures existing at the time the health consultation was initiated.
Technical Project Officer, SPS, SSAB, DHAC
The Division of Health Assessment and Consultation, ATSDR, has reviewed this health consultation and concurs with its findings.
Lisa C. Hayes
for Richard E. Gillig
Chief, SPS, SSAB, DHAC, ATSDR
The following assumptions were use to predict the concentration of MTBE that residents potentially could have inhaled through air as a result of the contaminant volatilizing from their well water into bathroom air during showering:
Ca = Cw x MT x FR x T
- Ca = Concentration of MTBE in air (µg/m3).
- Cw = Concentration of MTBE in water (124 µg/L).
- MT = Mass Transfer = 1 (represents 100% of MTBE volatilizing from water to air).
- FR = Flow Rate (rate of water flowing from the shower head at 12 L/ minute).
- T = Time in shower (10 minutes).
- V = Volume of the bathroom (10 m3) based on a small bathroom with dimensions of 7 feet by 7 feet by 8 feet).
TWA = 60 minutes divided by acute exposure time (10 minutes) x 24 hours.
ATSDR's acute Minimal Risk Level for MTBE in air = 2000 ppb or ~7211 µg/m3.
ATSDR's intermediate Minimal Risk Level for MTBE in air = 700 ppb or ~2524 µg/m3.
ATSDR's chronic Minimal Risk Level for MTBE in air = 700 ppb or ~2524 µg/m3.