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these concentrations in water supply systems. It Drinking Water and Toxic Enforcement Act of 1986 should be noted that the balancing of health effects for known human carcinogens and reproductive with technologic and economic considerations in toxins. They are found in Title 22 of CCR,Division MCLs may not be appiicable to the protection of a 2,Chapter 3. No-Significant-Risk Levels(NSRLs) raw water resource,as will be discussed later in are set at the one-in-100,000(10-5)incremental this paper. Secondary MCLS are derived from cancer risk level for carcinogens. '/1"of the No- human welfare considerations(e.g., taste,odor, Observable-Effect Level(NOEL)is used for repro- laundry staining)in the same manner as Primary ductive toxicants. Prop.65 criteria are established MCLS. in the form of a dose in units of micrograms per day of exposure(µg/d). These values are con- Drinking water MCLs are directly applicable to verted into 'lawful levels" in water by assuming 2 and enforceable by DHS on water suppliers. liters per day water consumption and 100 percent NICLs,both Primary and Secondary,are directly exposure to the chemical from drinking water,as applicable to ground and surtace water resources required by regulations contained in Title 22 of only when they are specifically referenced as water CCR,§§12721 and 12821. quality objectives in the pertinent Water Quality Control Plans. Due to their basis in health protec- 'J National Ambient Water Quality Criteria— tion, MCLS may also be used as water quality goals for other bodies of water designated as sources of These criteria are published by U.S. EPA under the drinking water in the Water Quality Control Plans. Clean Water Act to protect human health and welfare and freshwater and marine aquatic life. J Maximum Contaminant Level Goals(MCL Goals)— No-Adverse-Effect Levels are presented for non- carcinogens. Incremental cancer risk estimates for MCL Goals are promulgated by U.S.EPA under carcinogens are given at the 105, 106,and 10'(one- the National Primary Drinking Water Regulations in-ten-million)risk levels. Organoleptic levels are as the first step in establishing MCLS. By law, provided for some chemicals. Freshwater and MCL Goals must be set at levels which represent saltwater aquatic life criteria and toxicity informa- no adverse health risks. Thev are set at "zero' for tion are included. These criteria are found in: known and probable human carcinogens. 1) Quality Criteria for Water, 1986— the"Gold Book"; 7 State"Action Levels"— 2) the Ambient Water Quality Criteria volumes Action levels are published by DHS's Office of (1980,1984,1986, 1987,and 1989); Drinking Water and are based mainly on health 3) Quality Criteria for Water(1976)— effects. 106 incremental cancer risk estimates are the"Red Book";and used for carcinogens. Organoleptic(taste-and odor-based)values are also included for some 4) Water Quality Criteria, 1972— chemicals. Action levels are advisory to water the"Blue Book". suppliers. If exceeded,the supplier is urged to correct the problem or find an alternative raw 0 Health Advisories and Water Quality Advisories— water source. These advisories are published by U.S.EPA's J Proposition 65 Lawful Levels— Office of Water. Short-term(10 days or less),long- term(7 vears or less),and lifetime exposure health Proposition 65 criteria are established by the advisories for non-carcinogens and suspected California Environmental Protection Agency(Cal/ human carcinogens are included where data EPA),Office of Environmental Health Hazard sufficient for derivation of the advisories exist. Assessment(OEHHA)under the California Safe Incremental cancer risk estimates for known and Page 6 California's Water Quality Standards