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Toxics Criteria for Human Health and Aquatic Life

Posted By Johanna M. Bell, Thursday, December 15, 2016
Updated: Wednesday, December 14, 2016

The Clean Water Act requires that States update their toxic criteria every three years – a change made in the Clean Water Act in 1987 to reflect Congressional concern about the slow pace of improving toxics controls.  This applies to the human health criteria that are based on assumptions of fish consumption.  It also applies to criteria that are intended to protect aquatic life, such as threatened and endangered species.  

Criteria become the water quality goals for waters of the state, target for TMDLs, and may be used to establish limitations and other required actions such as Pollutant Minimization Plans and monitoring requirements for regulated point sources (i.e., stormwater, wastewater, potable water treatment facility permits, etc.).  Most of Idaho's human health standards for toxics in surface water have not been updated since 1992.

Since 1992, EPA has updated its guidance for deriving human health toxic water quality criteria in its Methodology for Deriving Ambient Water Quality Criteria for the Protection of Human Health (2000).  The 2000 Methodology increased the national default average fish consumption rate from 6.5 grams/day to 17.5 grams/day (the equivalent of 18.5 ounces of fish per month or 6.2 three ounce-servings each month).  EPA has also updated the CWA Section 304(a) recommended criteria to reflect this change in the national default fish consumption assumption.  For subsistence fishers, EPA recommended a national default consumption rate of 142.4 grams/day (the equivalent of 150 ounces per month or 50 three ounce-servings each month). In the 2000 Methodology, EPA also adopted guidance directing states to use local data on fish consumption when it was available.

EPA recently reviewed Washington State’s proposed toxics criteria and implementation guidance according to a court ordered date to approve or disapprove the criteria no later than November 15, 2016.  Most of Washington's human health standards for toxics in surface water also have not been updated since 1992. The new set of standards adopted by EPA is based on more recent science about health protection and fish consumption rates.  Specifically, the water quality standards now in place for Washington are based on the most sensitive population, typically tribes with treaty-protected rights, with a daily fish consumption rate of 175 grams/day (the equivalent of 185 ounces per month or 62 three ounce-servings each month) and a one-in-one million cancer risk level.

In the review, EPA also approved Washington’s revisions to its variance and compliance schedule provisions, which give the State and affected industries and municipalities some additional flexibility and time to implement the new standards while making reasonable progress in improving water quality.

Toxics rulemaking for Idaho was initiated in October 2012 in response to EPA’s disapproval of Idaho’s proposed criteria earlier that year.  Idaho concluded water quality toxics criteria rulemaking in May 2016 and submitted the toxics rulemaking package to EPA for review, approval, or disapproval on December 13, 2016.  


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