Impact of Key EPA Science Advisory Board Technical Findings on State Nutrient Criteria Development

The EPA Science Advisory Board Ecological Processes and Effects Committee met on September 9-11, 2009 to review new draft guidance for the derivation of numeric criteria for nutrients. The new draft guidance, “Empirical Approaches for Nutrient Criteria Derivation”, represented EPA's latest attempt to formalize the nutrient criteria development approach it has been promoting through its Regional Technical Advisory Groups (RTAGs). Contrary to its prior guidance, the new EPA approach does not consider whether nutrient loads trigger excessive plant growth but assumes that there exists a direct relationship between invertebrate populations and ambient nutrient levels. The draft guidance suggested that simplified regression methods are appropriate for numeric criteria derivation in all water bodies. The peer review committee unanimously rejected the use of such simplified approaches for establishing nutrient criteria, concluding that those methods failed to establish a “cause and effect” relationship between nutrients and the impact of concern.