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HEALTH CONSULTATION

Evaluation of Exposure to Tetrachloroethylene (PCE) in an Irrigation Well

STEELE LANE ELEMENTARY SCHOOL
SANTA ROSA, SONOMA COUNTY, CALIFORNIA


SUMMARY

In February 2002, the California Department of Health Services (CDHS) Environmental Health Investigations Branch (EHIB), was asked by the County of Sonoma Environmental Health Department to evaluate the potential health risk associated with exposure to tetrachloroethylene (PCE) in an irrigation well at the Steele Lane Elementary School in Santa Rosa. The content of the correspondence between Sonoma County and CDHS is the basis of this health consultation [see attached letter (Appendix A)]. CDHS has a cooperative agreement with ATSDR, and the letter is being forwarded to ATSDR as a health consultation for its concurrence.


BACKGROUND AND STATEMENT OF ISSUES

In February 2002, CDHS was asked to evaluate the potential health risk to children at Steele Lane Elementary School from irrigation well water contaminated with PCE. The PCE was detected at 7.2 ppb (parts per billion) in an irrigation well at the school, during an investigation conducted by the North Coast Regional Water Quality Control Board [see attached letter for details (Appendix A)]. The municipal water supply is the source of drinking water at the Steele Lane Elementary School.


DISCUSSION

CDHS estimated an exposure dose for children/students at Steele Lane Elementary School using a worst-case scenario, assuming the water is used for drinking and bathing activities [see attached letter (Appendix A)]. We assumed that exposure from inhalation and dermal contact are equivalent to the ingestion dose. The estimated combined exposure dose (0.0003 mg/kg/day) for a young child is below health standards (Minimal Risk Level) for non-cancer health effects. Thus, exposure to the irrigation well water should not have caused non-cancer health effects to children at the Steele Lane Elementary School.

CDHS evaluated cancer health effects in terms of an increased risk of developing cancer, from which exposure is averaged over a lifetime. The estimated increased cancer risk for children at Steele Lane School is 2.5 x 10-7 or about 2 in 10,000,000. This is considered "no apparent increased cancer risk" [see attached letter for details (Appendix A)].


CHILD HEALTH INITIATIVE

ATSDR and CDHS recognize that infants and children may be more sensitive to health effects caused by environmental contaminants, and believe that it is important to search for additional information that will increase our understanding of contaminants, and ensure that children’s health is protected. Our evaluation focused on potential exposures to children at the Steele Lane Elementary School.


CONCLUSIONS

Based on the limited data, CDHS evaluated the potential health effects from exposure to 7.2 ppb of PCE in an irrigation well formerly used at the Steele Lane Elementary School. We concluded that exposure to PCE through irrigation activities at the school did not pose public health hazard.


PUBLIC HEALTH RECOMMENDATIONS AND ACTIONS

The Public Health Recommendations and Actions Plan (PHRAP) for this site contain a description of actions taken, to be taken, or under considerations by ATSDR and CDHS at and near the site. The purpose of the PHRAP is to ensure that this health consultation not only identifies public health hazards, but also provides a plan of action designed to mitigate and prevent adverse health effects resulting from exposure to hazardous substances in the environment.


ACTION COMPLETED

CDHS responded to a request by the County of Sonoma Environmental Health Department to evaluate potential health risk to students at the Steele Lane Elementary School from exposure to PCE in irrigation well water.


PREPARERS OF REPORT

Environmental and Health Effects Assessors:

Tracy Barreau, R.E.H.S
Environmental Health Scientist
Impact Assessment contractor to the
Environmental Health Investigations Branch
California Department of Health Services

Marilyn C. Underwood, Ph.D.
Chief Site Assessment Section
Environmental Health Investigations Branch
California Department of Health Services


ATSDR Regional Representatives

William Nelson
Gwen Eng
Libby Levy
Regional Representatives, Region IX
Agency for Toxic Substances and Disease Registry


ATSDR Technical Project Officer:

Alan W. Yarbrough
Environmental Health Scientist
Division of Health Assessment and Consultation
Superfund Site Assessment Branch, State Programs Section


APPENDIX A: LETTER DATED MARCH 8, 2002


State of California–Health and Human Services Agency
DEPARTMENT OF HEALTH SERVICES

March 8, 2002

Jonathan Krug, MPH, REHS
Director of Environmental Health
County of Sonoma Environmental Health Department
1030 Center Drive, Suite A
Santa Rosa, CA 95403-2067

Dear Mr. Krug:

The Environmental Health Investigations Branch of the California Department of Health Services (CDHS), was asked by the County of Sonoma Environmental Health Department to evaluate potential exposures to PCE (tetrachloroethylene) contamination discovered in a irrigation well used at the Steele Elementary School. CDHS conducts health assessment activities under a cooperative agreement with the federal Agency for Toxic Substance and Disease Registry.

According to our conversation, PCE was detected at 7.2 ppb (parts per billion) in an irrigation well formerly used at the Steele Lane Elementary School. The PCE contamination was discovered on February 8, 2002, during an investigation being conducted by the North Coast Regional Water Quality Control Board. As a result, the school was advised not to use the well for irrigation purposes. CDHS has not reviewed the laboratory results of the irrigation well or any other data relating to the PCE investigation, thus our evaluation is based on verbal communication of the irrigation well results. We would advise you to review the data quality and retest the well to verify the results.

The school receives its drinking water from municipal sources that are tested and required to meet drinking water standards. Therefore, children and teachers at Steele Lane School are not drinking PCE-contaminated water. The concern is that a child could potentially be exposed to PCE in areas that were irrigated with the contaminated well water. It is our understanding the irrigation activities at the school took place during the early morning, a few months out of the year. PCE is a volatile organic chemical that volatilizes rapidly to the atmosphere due to its high vapor pressure and Henry's law constant. The low level (7.2 ppb) of PCE detected in the irrigation well, and the fact that PCE volatilizes rapidly and will be dispersed and diluted in the open air, reduce the likelihood that a child would have been exposed to measurable levels of PCE from the irrigation activities at the school. Exposure from irrigation water would be considerably less than if someone were drinking or showering with it.

As a first assessment, we evaluated the worst case scenario that the water is ingested and used for showering, because this is more straight forward calculation and would present an overestimation of the exposure. We used the following assumptions:

  • A young child ingests 1 liter of the irrigation water per day (sole drinking water source)
  • 180 days per year (number of school days per year)
  • 7 years of exposure (kindergarten through 6th grade)
  • Inhalation and dermal exposures equal to ingestion dose

The estimated combined (ingestion, dermal contact, inhalation) exposure dose (0.0007 mg/kg/day) for a young child is below health standards (Minimal Risk Level) for non-cancer health effects. The exposure dose (0.0007 mg/kg/day) should be considered an overestimation, because actual exposures would have been much lower. Thus, exposure to the irrigation well water (under a worst-case scenario) should not have resulted in non-cancer health effects to children at Steele Lane Elementary School.

PCE is considered a potential carcinogen. Cancer health effects are evaluated in terms of an increased risk of developing cancer, from which exposure is averaged over a lifetime. It is scientifically questionable to estimate an individual's "lifetime increased cancer risk" from only one data point. However, CDHS estimated a child's increased cancer risk using the worst-case exposure scenario discussed above, as a point of reference. The estimated increased cancer risk for children at Steele Lane School is 2.5 x 10-7 or about 2 in 10,000,000. This is considered "no apparent increased cancer risk".

Based on the limited data, CDHS concludes that exposure to irrigation well water containing 7.2 ppb PCE, at the Steele Lane Elementary School did not pose a public health hazard.

If you have any questions please do not hesitate to call Tracy Barreau at (510) 622-4489 or Marilyn Underwood, Ph.D. at (510) 622-4415.

Sincerely,

 

Tracy Barreau, REHS
Environmental Health Scientist
Environmental Health Investigations Branch

 

Marilyn C. Underwood, Ph.D.
Chief, Site Assessment Section
Environmental Health Investigations Branch

cc:

Mark Bartson
North Coast Regional Water Quality Control Board
5550 Skylane Boulevard, Suite A
Santa Rosa, CA 95403

Luis Rivera
North Coast Regional Water Quality Control Board
5550 Skylane Boulevard, Suite A
Santa Rosa, CA 95403

Mary Maddux-Gonzalez, M.D., M.P.H.
Health Officer
County of Sonoma Department of Health Services
625 5th Street
Santa Rosa, CA 95404


CERTIFICATION

This Evaluation of Exposure to Tetrachloroethylene (PCE) in an Irrigation Well at the Steel Lane Elementary School Health Consultation was prepared by the California Department of Health Services under a 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 begun.

Alan W. Yarbrough
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.

Roberta Erlwein
Chief, State Program Section, SSAB, DHAC, ATSDR

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