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Inorganic chemicals are elements or compounds found in water supplies. They may occur naturally in the geology or they may be caused by mining, industry or agricultural activities. It is common to have trace amounts of many inorganic chemicals in water supplies. In larger amounts, however, inorganic chemicals can be dangerous and can cause a variety of damaging effects to the liver, kidney, nervous system, circulatory system, gastrointestinal system, bones, and skin, depending upon the chemicals and level of exposure. Pregnant women and infants are especially susceptible to harm from inorganic chemicals. As a result, EPA has established safety levels for each of them, called "maximum contaminant levels" or "MCLs."

Do The Inorganic Chemical Regulations Apply to Your Community?

Yes, all community public water supply systems and non-transient, non-community water systems must monitor for regulated inorganic chemicals in their water supplies unless they have received a waiver from the state in which they operate. Non-transient, non-community public water systems are those that are not community water systems and that regularly serve at least 25 of the same persons over 6 months per year, (e.g., schools, businesses with their own system). Under the current rules, sampling for inorganic chemicals is required every three years from each sampling point for groundwater supplies and every year from each sampling point for surface water supplies. A sampling point for groundwater systems is an entry point to the drinking water distribution system from a treated well. A sampling point for surface water systems refers to an entry point to the drinking water distribution system from a water source or treatment plant.

Actions Your Community Should Be Taking

At present there are 17 regulated inorganic chemicals for which your community must test. They are listed along with their MCLs at the end of this section. Asbestos and fluoride are included in this category, but because their rules are somewhat different they have been addressed separately in this Guide.

Public water systems must take inorganic chemical samples according to a nine-year cycle called a "compliance cycle," and three 3-year periods called "compliance periods." Groundwater-based public water systems must take one sample every three years (once per compliance period) for each regulated inorganic chemical, except asbestos, nitrate, and nitrite. Surface water-based public water systems must sample annually for each regulated chemical, except asbestos, nitrate, and nitrite.

Asbestos, nitrate, and nitrite are subject to different sampling requirements. Each community and non-transient, non-community water system is required to take samples for asbestos during the first three-year compliance period of each nine-year compliance cycle. All public water systems and non-transient, non-community water systems with groundwater sources must sample annually for nitrate. Systems with surface water sources must sample quarterly for nitrate. All public water supplies, including transient water supplies, were required to sample for nitrite during the first compliance period (January 1, 1993 - December 31, 1995) and thereafter at an interval designated by the

The inorganic chemical regulations allow public water systems to obtain waivers from the monitoring requirements (except for nitrate and nitrite, which cannot be waived). In order to obtain a waiver surface water systems must have monitored annually for at least three years and groundwater systems must have performed at least three rounds of monitoring. In addition, both surface water and groundwater systems must not have exceeded the MCLs for any of the inorganic chemicals in any previous samples. A waiver either eliminates or reduces monitoring requirements. A public water system with a waiver for inorganic chemicals would need to sample only once during each compliance cycle or once every nine years beginning January 1, 1993.

More recent regulations (called "Phase V") were finalized in July, 1992 and became effective in January, 1993 for large systems with greater than 150 service connections. The regulations require small public water supply systems (those with less than 150 hookups) to begin monitoring between 1996 and 1998. The Phase V regulations also allow a public water system to apply for a waiver after three monitoring rounds if the inorganic chemicals are not detected. As with the Phase II regulations, an approved waiver for inorganic chemicals would reduce sampling to once every nine years.

If testing reveals you have exceeded the MCLs for any of the regulated inorganic chemicals, you must notify the appropriate state agency and complete public notices as required. In addition, you must begin monthly monitoring in the first quarter after a violation and work with the state agency and/or an engineer to determine the best way to reduce the level of the contaminant in your water supply. In addition to considering a new treatment process, you may need to consider improving your present treatment process, mixing your contaminated supply with another supply that does not exceed the MCL or obtaining a new source of water. In order to continue to use the water supply while solutions to the MCL exceedances are being explored, you should request an exemption from the state agency. Contact resource agencies listed in the back of this booklet for help in planning and finding financing for your system improvements.

Additional Information

The inorganic chemicals requirements are published in Title 40 Code of Federal Regulations, Parts 141.11, 141.23, 141.62.

Your state agency can provide some additional information on any of the individual inorganic chemicals.

See separate pages of this booklet for information on Asbestos, Fluoride, Lead, and Copper.

For further information on the federal requirements, contact the EPA Safe Drinking Water Hotline. Telephone: 1/800/426-4791.

(See Resource Section for drinking water contacts)

Maximum Contaminant Levels (MCL) for Inorganic Chemicals

mg/l = milligrams per liter
fibers/l = number of fibers per liter