On June 26, 2019, EPA published a Notice of Proposed Rulemaking requesting comment on a proposed Maximum Contaminant Level (MCL) for perchlorate under the Safe Drinking Water Act (SDWA). Perchlorate is both a man-made and naturally-occurring chemical, most commonly found in industrial operations associated with the use or manufacture of rocket fuel, missiles and fireworks. Perchlorate inhibits the uptake of iodide to the thyroid and has been detected in certain public water supply systems, primarily in the western United States. In its Notice, EPA proposes an MCL of 56 µg/L, but at the same time requests public comment on whether the MCL should be set at a higher or lower standard, or whether the agency should re-evaluate its decision to regulate perchlorate based on updated data. This rule, if finalized, could affect thousands of public water systems that would be required to comply with the new standard, as well as state and tribal agencies responsible for drinking water regulatory development and enforcement.
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