The State of California Office of Environmental Health and Hazard Assessment (OEHHA) recently set a new Public Health Goal for Perchlorate at 1 ppb. To help clarify, a public health goal is not a regulatory limit but is designated as a contaminant level where “...adverse health effects are not expected to occur.” This limit can be determined using ion chromatography without MS detection (link to downloadable application note).
The California Safe Drinking Water Act of 19961 requires OEHHA to develop PHGs based exclusively on public health considerations. In turn, the PHGs published by OEHHA are considered by the State Water Resources Control Board in setting drinking water standards (Maximum Contaminant Levels, or MCLs).
Setting Guidance Levels for Drinking Water
As per the Guide to Public Health Goals for Chemicals in Drinking Water, (downloadable PDF), for perchlorate, the California Department of Public Health (CDPH) uses this new determination (among others) to set guidance levels for drinking water. By law, CDPH must set the state’s regulatory standards, Maximum Contaminants Levels (MCLs) as close as possible to the PHG levels that OEHHA establishes. However, CDPH must also consider the cost and technological feasibility of treating or preventing chemical contamination. The OEHHA must also develop a PHG for each drinking water contaminant that is regulated with an MCL or for a contaminant for the first time.
Maximum Contaminant Levels are reviewed by CDPH at least every five years and amended, if necessary, to make them as close to the corresponding PHG as is feasible. The CDPH could amend an MCL if the PHG evaluation indicates that the contaminant is more or less toxic than was previously believed, or if new technology is available to reduce concentrations to levels closer to the PHG.
Is Water Safe to Drink if Contaminant Levels Exceed Public Health Goals?
In general, as long as drinking water complies with all MCLs it is considered safe to drink, even if some contaminants exceed PHG levels. A PHG represents a health‐protective level for a contaminant that CDPH and California’s public water systems should strive to achieve if it is feasible to do so. However, a PHG is not a boundary line between a safe and dangerous level of a contaminant, and drinking water can still be considered acceptable for public consumption even if it contains contaminants at levels exceeding the PHG.
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