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Human Health Criteria
Methylmercury Fish Tissue Criterion
Draft Guidance for Implementing the January 2001 Criterion
Fact Sheet; August 2006; EPA 823-F-06-011
EPA published for public comment a draft of the Guidance for Implementing the January 2001 Methylmercury Water Quality Criteria. You can download the Guidance document. When final, this document will help protect waters by giving state, territory, and authorized tribal water quality programs guidance on how to adopt and implement the fish tissue-based methylmercury water quality criteria.
Background
In January 2001, we published a new water quality criterion for mercury that for the first time bases the human health criterion on fish and shellfish tissue rather than on a water column value. This fish and shellfish tissue criterion approach for setting water quality standards creates several challenges, such as translating the fish tissue residue value into a water concentration and ultimately into NPDES permit limits.
In a 2001 Federal Register announcement, EPA stated its intent to develop guidance on implementing the criterion to address these issues. Subsequently, EPA formed a workgroup of representatives from state environmental agencies, EPA Regions, and headquarters air and water programs to develop the draft guidance.
About this Draft Guidance Document
The draft guidance, entitled the Guidance for Implementing the January 2001 Methylmercury Water Quality Criterion, helps states implement the 2001 Methylmercury Water Quality Criterion. This guidance generally consolidates existing guidance on water quality standards, TMDLs, and permits where relevant to mercury. The new aspect of the guidance is a suggested approach for implementing the new methylmercury criterion that does not necessarily result in all NPDES discharges reducing the level of mercury in the discharge. Instead, for NPDES discharges that contribute only a very small amount of the mercury to a watershed, the suggested approach consists of holding the discharges at current levels. This suggested approach mirrors current practice where wasteload allocations are developed for TMDLs where point sources are only small contributors to the total loading in a watershed. This approach also does not require a site-specific bioaccumulation factor that can be costly to develop.
How to Get Additional Information
You can download the Draft Guidance for Implementing the January 2001 Methylmercury Water Quality Criterion (EPA 823-B-04-001)