PRELIMINARY HEALTH REVIEWS IN RANCHO CORDOVA, SACRAMENTO COUNTY, CALIFORNIA
RANCHO CORDOVA, SACRAMENTO COUNTY, CALIFORNIA
The Environmental Health Investigations Branch (EHIB), within the California Department of Health Services (CDHS), under a cooperative agreement with the Agency for Toxic Substances and Disease Registry (ATSDR), is conducting public health assessment activities on the Aerojet-General Corporation (Aerojet) Superfund site in Sacramento County, California (See Figure 1). A preliminary public health assessment written in December 1988 recommended that when additional environmental information and data became available, ATSDR would make another assessment (1). A site review and update written in March 1993 also recommended a public health assessment be conducted when more data became available (2).
This health consultation is one in a series that will be performed as part of the ATSDR enhanced
public health assessment process at this site. During this process, data and information on the
release of hazardous substances and their impact on public health will be evaluated. Five health
consultations on perchlorate exposure in the drinking water supply have recently been written as
part of this series (3-7). In this health consultation, we will focus on three preliminary reviews of
health outcome data gathered on individuals living in areas potentially affected by the perchlorate-contaminated drinking water. These reviews focus on specific health outcomes related to
biologically-plausible effects from exposure to perchlorate and surveys performed at the request
of concerned residents. These reviews include: data from the Genetic Disease Branch of CDHS
pertaining to neonatal hypothyroidism, hospital discharge data from the Office of Statewide
Health Planning and Development (OSHPD) of CDHS pertaining to goiter, agranulocytosis and
aplastic anemia and information from the California Cancer Registry for cancer in general, and specifically for cancers of the thyroid and blood cells.
Aerojet began operation in the Rancho Cordova area of California in 1951. Since that time, Aerojet has manufactured liquid and solid propellants for military and commercial rocket systems and has fabricated, assembled, tested and rehabilitated rocket engines (1). In addition, between 1974 and 1979, Cordova Chemical Company, a wholly-owned subsidiary of Aerojet, manufactured paint components, herbicides, and pharmaceutical products within the facility boundaries. Over the years, Aerojet and Cordova Chemical disposed of hazardous waste by burial, open dumping, discharge into unlined ponds, and injection into deep underground wells (1). Monitoring demonstrated perchlorate in the groundwater, which was thought to have arisen from ammonium perchlorate, a main component of solid rocket fuel. In addition to the natural migration of perchlorate-contaminated groundwater from the site, Aerojet has been reinjecting water treated to remove trichloroethylene, but still contaminated with perchlorate, back into the groundwater at the site's western and northern boundary. Some of these discharges, including perchlorate, moved off-site of the Aerojet facility boundary (Figure 1) and contaminated several drinking water wells of the Arden Cordova Water District (7). The Regional Water Quality Control Board (RWQCB), the lead regulatory agency, is also investigating other potential sources of the perchlorate, such as the McDonnell Douglas or Purity Oil sites.
The Arden Cordova Water Service is composed of two distinct systems, the Arden System and the Cordova System (Figure 1). These systems are not interconnected (i.e., the wells located in the Cordova System serve only the Cordova System customers). The Cordova System has been impacted by the perchlorate contamination, whereas the Arden System is located several miles west of the contamination and thus it is unlikely that it will ever be affected (7). The Cordova System supplies water to 11,650 connections, approximately 36,500 customers, mostly family residences and commercial businesses (8). It is believed that perchlorate first contaminated wells in the Cordova System sometime in the late 1980s; however, it was not until February 1997 that the distribution of water from affected wells was stopped. Currently, drinking water wells 13, 15 and 16 remain closed (due to levels of 220, 95 and 210 parts per billion (ppb) perchlorate, respectively). Additionally, three wells which initially were closed in April 1997 [wells 11 and 14 (4.4 ppb perchlorate each) and well 19 (6.8 ppb perchlorate)] have been reopened and are again serving customers, as of June 1997 (7). A prior health consultation concluded that a completed exposure pathway to perchlorate-contaminated drinking water for residents and employees served by the Arden Cordova Water District existed and that this water may have posed a health hazard to exposed individuals during the length of time that these wells were in use (7).
Currently, there remains much debate over the health effects related to perchlorate ingestion and considerable uncertainty pertaining to the levels of perchlorate which are believed to be of danger to the public health. At present, the U.S. Environmental Protection Agency (U.S. EPA) has a provisional oral reference dose (RfD) for perchlorate compounds (0.0001 mg/kg/day) which is an estimate of a daily exposure to the human population that is likely to be without appreciable risk of deleterious effects during one's lifetime (10). However, this level may be a more conservative estimate by a factor of 1000 due to toxicological uncertainties involved. Additionally, the detection limit for perchlorate in drinking water was just recently decreased by the availability of more advanced methods of testing, so that wells which were previously thought to be uncontaminated were more recently found to contain small amounts of perchlorate. These factors may have contributed to the appearance that people may have been receiving perchlorate-contaminated drinking water for almost ten years without any prior health agency response.