Numeric Nutrient Criteria Development: Challenges and Impacts

Despite current efforts to limit discharges of nitrogen and phosphorus, these nutrients are still a leading cause of impairments to the nation's surface waters. In reaction to legal pressure from environmental groups, and limited success with its own national nutrient strategy, the U.S. Environmental Protection Agency (EPA) is proposing new, very low criteria for total nitrogen (TN) and total phosphorus (TP) – as low as 0.12 mg/L TN and 0.01 mg/L TP for certain regions. These new criteria sparked considerable concern and debate on nutrients throughout the nation. This paper explores the challenges confronting state and federal efforts to develop scientifically defensible numeric nutrient criteria as environmental advocates push for the implementation of numeric standards while utilities, agriculture and industries question the methodologies used to develop the criteria, the implementation costs, their effectiveness as a response to the nation's eutrophication problems; and the equity with which the criteria will be applied.