Perchlorate Contamination in the Citizens Utilities'
Suburban and Security Park Water Service Areas
RANCHO CORDOVA, SACRAMENTO COUNTY, CALIFORNIA
Based upon the information reviewed, there was a completed exposure pathway to perchlorate-contaminated water in the Citizens Utility Suburban System. This completed exposure pathway occurred when water was delivered from the Mather Main Base Water System, which is known to be contaminated with perchlorate, to the Suburban System for several months in 1995 and 1996. Otherwise, the water that supplies the Suburban System customers comes from wells that have not had any quantifiable levels of perchlorate detected in them. Thus, most Suburban System customers have never been exposed to any perchlorate-contaminated water.
Residents who lived near and employees who worked at businesses near the Mather Main Base intertie may have been exposed on a regular basis to the perchlorate when they drank water and washed or showered with the water. Other exposures occurred over a short duration resulting in a very low dose to the customers and visitors who occasionally frequented the business establishments located near the Mather Main Base intertie.
It is difficult to predict when the perchlorate first contaminated the Mather Main Base wells but it may have been as early as 1987. In March 1997, the perchlorate concentration in two Mather Main Base drinking water wells (Main Base wells #1 and 2) exceeded a concentration (4 to 18 ppb) suggested by the USEPA provisional reference dose based on a 70 kg individual consuming two liters of water a day. There is currently a three hundred to thousand-fold uncertainty factor incorporated into the provisional reference dose. Since the uncertainty factors are supposed to account for the somewhat limited toxicological information, it is conceivable that as more toxicological data becomes available, a change in the (provisional) reference dose may occur.
The estimated dose for a adult resident or worker (only when well #2 was the lead well) of the Suburban System who was exposed to water from the intertie with the Mather Main Base exceeds the provisional reference dose range which means that noncancer (thyroid depression) health effects may have occurred when the adult resident or worker was exposed to water from these wells. However, because there is a very large uncertainty factor associated with the provisional reference dose and the estimated doses do not approach the NOAEL, it is unlikely that these exposures did cause any noncancer health effects. This intertie is no longer being used, thus any noncancer health effects that may have occurred should no longer be occurring now that the exposure has ceased.
The estimated dose for a frequent adult customer/visitor or worker (when well #1 was the lead or there was a four well rotation) to a business served by the Suburban System and who was exposed to water the intertie with the Mather Main Base does not exceed the provisional reference dose range. This means that noncancer (thyroid depression) health effects would not have occurred to the frequent adult customer/visitor drinking or washing with water from the Mather intertie.
Based upon the information available at the time this health consultation was written, CDHS concludes that well water received through the intertie with the Main Base Water System for several months in 1995 and 1996 posed a health hazard when the water was delivered to the Suburban System. Since the water from this intertie is longer being used, there is no current health hazard from perchlorate to Suburban System users. Additionally, the well water in the Security Park System does not pose a health hazard due to perchlorate.
The Public Health Recommendations and Actions Plan (PHRAP) for this site contains a description of actions taken, to be taken, or under consideration 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 human health effects resulting from exposure to hazardous substances in the environment. The CDHS and ATSDR will follow-up on this plan to ensure that actions are carried out.
- Citizens Utility sent a notice to their Suburban System customers in March about the finding of no quantifiable levels of perchlorate in the Suburban wells.
- CDHS prepared a fact sheet about perchlorate and health. CDHS made this fact sheet available to the affected water purveyors including Citizens Utility Company of California.
- The Air Force and the Perchlorate Study Group (a number of manufacturers and users of perchlorate) are sponsoring an investigation into fate and transport question regarding perchlorate. For instance, they will investigate if is perchlorate taken up and bioconcentrated by vegetable crops and the skin permeability of perchlorate.
- The Air Force and the Perchlorate Study Group are sponsoring a series of animal studies to address some of the information lacking in understanding perchlorate toxicology. CDHS cooperative agreement staff along with other state and federal scientists, were asked by the Air Force to recommend and oversee the planning of the animal studies. As of August 1997, the study protocols have been finalized and the process of choosing a laboratory to conduct the studies is underway. A report on the studies is expected in mid-summer 1998.
- Continue communicating with the Citizens Utility Suburban Systems water customers about the perchlorate issue.
- Continue monitoring drinking water wells for perchlorate, and discontinue using a well that has levels of 18 ppb or greater of perchlorate.
- Consider conducting a dose reconstruction exposure investigation of perchlorate exposure in the Suburban System.
- If indicated based on new toxicological information, review toxicological evaluation of past perchlorate exposures in the Suburban System.
- Be prepared to address the possible contamination of the Security Park System.
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ENVIRONMENTAL AND HEALTH EFFECTS ASSESSORS:
Marilyn C. Underwood, Ph.D.
Environmental Health Investigation Branch
California Department of Health Services
COMMUNITY RELATIONS COORDINATOR:
Jane Riggan, M.S.W.
Public Health Social Work Consultant II
Environmental Health Investigations Branch
California Department of Health Services
ATSDR REGIONAL REPRESENTATIVE
Senior Regional Representative
Office of Regional Operations, ATSDR - Region IX
ATSDR TECHNICAL PROJECT OFFICER:
William Greim, M.S., M.P.H.
Division of Health Assessment and Consultation
Superfund Site Assessment Branch, State Programs Section
The Perchlorate Contamination in the Citizens Utilities' Suburban and Security Park Water Service Areas, Aerojet-General Corporation 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 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.
Chief, SPS, SSAB, DHAC, ATSDR