PHG Exceedance Reports 2010
Under the Calderon-Sher Safe Drinking Water Act of 1996 (the Act), water utilities are required to prepare a report every three years for contaminants that exceed public health goals (PHGs) (Health and Safety Code Section 116470 (2)[b]). The numerical health risk is to be presented with the category of health risk, along with a plainly worded description of these terms. PHGs are published by the Office of Environmental Health Hazard Assessment (OEHHA)(Health and Safety Code Section 116365) as concentrations of contaminants in drinking water that OEHHA, using current risk assessment principles, practices and methods, considers to pose no significant health risk if consumed for a lifetime. This report is prepared by OEHHA to assist the water utilities in meeting their requirements.
Numerical health risks. The tables that follow summarize health risks for chemical contaminants in drinking water that have PHGs and state and/or federal regulatory standards. The regulatory standards are maximum contaminant levels (MCLs). The Act also requires that OEHHA publish 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 has been publishing PHGs as they are completed since 1997 and the entire list published to date is shown in Table 1 of the Health Risk Information for
Public Health Goal Exceedance Reports.
The Act requires that for chemical contaminants with California MCLs that do not yet have 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 United States 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 no more than one-in-a-million excess cancer risk (110-6) level for a lifetime of exposure. Chemicals with MCLGs but no PHGs are presented in Table 2 of the Health Risk Information for
Public Health Goal Exceedance Reports. The cancer risks shown are based on the U.S. EPA’s evaluations.
Health risk categories. The following information can be used 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 (unless otherwise stated), rather than high doses from a single or short-term exposure. The potential health effects are the most sensitive adverse effects that occur when chemical exposure reaches a sufficient level and duration to produce toxicity. Health goals that protect against these risks also protect 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 effects 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 (minutes to days).
Subchronic toxicity – adverse health effects that develop after repeated or longer-term exposures to a chemical (days to months).
Carcinogenic - capable of producing cancer.
Chronic toxicity - adverse effects that usually develop gradually from low levels of chemical exposure over a long period of time (months to years).
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 adversely affecting or destroying parts of 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 (for example, 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, lowered fertility, sperm production, length of pregnancy, and milk production.
The tables further note whether the health risk category is based on human or animal data. Data on health effects of toxic substances are usually obtained from studies on laboratory animals.
For more information on health risks: The adverse health effects for each chemical with a PHG are summarized in each PHG technical support document. These documents are available on the OEHHA Web site.
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 U.S. EPA Office of Ground Water and Drinking Water's home page at http://www.epa.gov/OGWDW/hfacts.html.