Health Risk Information for Public Health Goal Exceedance Reports
[06/10/1998]

The following tables summarize health risks for chemical contaminants in drinking water that have regulatory standards, or maximum contaminant levels (MCLs). Under the Calderon-Sher Safe Drinking Water Act of 1996, utilities are required to prepare a report for contaminants that exceed public health goals. The first report is due July 1, 1998, and subsequent reports are due every three years (Health and Safety Code section 116470 (2)[b]). The section states that the numerical health risk be presented along with the category of health risk, and a plainly worded description of these terms.

The Act also requires that the Office of Environmental Health Hazard Assessment (OEHHA) adopt "public health goals" (PHGs) based on health risk assessments using the most current scientific methods. As defined in statute, PHGs for noncarcinogenic chemicals in drinking water are set at a concentration "at which no known or anticipated adverse health effects will occur, with an adequate margin of safety." For carcinogens PHGs are set at a concentration that "does not pose any significant risk to health." PHGs provide one basis for revising MCLs, along with cost and technological feasibility. OEHHA in 1997 established the first 27 PHGs for 26 chemicals, as shown in Table 1.  (Download tables 1 and 2 as Adobe Acrobat PDF files)

The Act requires that for chemical contaminants with MCLs that do not yet have California PHGs, water utilities will use the federal maximum contaminant level goal (MCLG) for the purpose of complying with the requirement of public notification. MCLGs, like PHGs, are strictly health based and include a margin of safety. One difference, however, is that the MCLGs for carcinogens are set at zero because the U.S. Environmental Protection Agency (U.S. EPA) assumes there is no absolutely safe level of exposure to them. PHGs, on the other hand, are set at a level considered to pose no significant risk of cancer; this is usually a one-in-a-million excess cancer risk (1´ 10^-6) for a lifetime of exposure. Chemicals with MCLGs are presented in Table 2.  (Download tables 1 and 2 as Adobe Acrobat PDF files)

Health risk categories
The following information will be helpful for presenting the health risk categories in "exceedance reports." The health risks shown in the tables are based on long-term exposures to low levels of contaminants as would occur with drinking water, rather than high doses from a single or short-term exposure. These are the first or most sensitive adverse effects that occur when chemical exposure reaches a sufficient level and duration to produce toxicity. Basing health goals to protect against these risks also protects against health risks that would occur from short-term exposures. For most health risk categories, the specific health outcome, or the organ or system that is affected, is also given. The health terms are given in nontechnical terms when possible, and the categories are described below.

• Acute toxicity - adverse health effects that develop after a short-term exposure to a chemical.

• Carcinogenic - capable of producing cancer.

• Chronic toxicity - adverse effects that usually develop gradually from low levels of chemical exposure and that persist for a long time.

• Developmental toxicity - adverse effects on the developing organism that may result from exposure prior to conception (either parent), during prenatal development, or postnatally to the time of sexual maturation. Adverse developmental effects may be detected at any point in the life span of the organism. The major manifestations include: (1) death of the developing organism, (2) structural abnormality (birth defects), (3) altered growth, and (4) functional deficiency.

• Neurotoxic - capable of destroying or adversely affecting the nervous system, or interfering with nerve signal transmission. Effects may be reversible (for example, effects on chemicals that carry nerve signals across gaps between nerve cells) or irreversible (destruction of nerve cells).

• Reproductive effects - the occurrence of adverse effects on the reproductive system of females or males that may result from exposure to environmental agents. The toxicity may cause changes to the female or male reproductive organs, the regulating endocrine system, or pregnancy outcomes. Examples of such toxicity may include adverse effects on onset of puberty, egg production and transport, menstrual cycle normality, sexual behavior such as sexual urge, and lowered fertility, sperm production, length of pregnancy, and milk production.

The table further notes whether the health risk category is based on human or animal data. Data on health effects of toxicants is usually obtained from studies on laboratory animals.

For more information on health risks
The adverse health effects for each chemical are summarized in each PHG document. These will be available on the OEHHA Web site http://www.oehha.org or may be ordered in print. (Call OEHHA at 510/540-3063 for details.) Also, U.S. EPA has consumer and technical fact sheets on most of the chemicals having MCLs. For copies of the fact sheets, call the Safe Drinking Water Hotline at 1-800-426-4791, or explore the Office of Ground Water and Drinking Water's home page at http://www.epa.gov/OGWDW/hfacts.html.

• Download tables 1 and 2 as Adobe Acrobat PDF files

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Last Updated June 10, 1998