Protecting Human Health and Indiana’s Lakes and Streams from the Impacts of Excess Nutrients

The Regulatory Background

The Clean Water Act (CWA), as amended in 1976, established a national goal of achieving water quality that provides for the protection and propagation of aquatic organisms, wildlife, and recreation in and on the water. In 1996, the U.S. Environmental Protection Agency’s (U.S. EPA’s) National Water Quality Inventory identified excess amounts of nutrients as the second leading cause of impairment in rivers and streams and as the primary cause of impairments in lakes and reservoirs.

Many streams in Indiana have been identified on the state’s CWA Section 303(d) list of impaired water due to excess nutrients. To address these impairments, the U.S. EPA in 2000 developed nutrient criteria to protect streams for total nitrogen as nitrogen (TN), total phosphorus as phosphorus (TP), periphyton and seston chlorophyll a (CHLa), and turbidity.

These criteria are based on U.S. EPA Aggregate Nutrient Ecoregions and Level III Ecoregions, which are areas with similar geographic features such as topography, soils, geology, land use, and biogeography. To develop the criteria, the U.S. EPA reviewed selected data and utilized the frequency distribution approach to develop criteria based on the lower 25th percentile value for all data or the 75th percentile from reference sites for each causal variable. However, few of the available data from Indiana were included in the calculation or — as was the case for CHLa — little or no data existed for many of the ecoregions, including in Indiana. As a result, the proposed nutrient, CHLa, and turbidity criteria may not accurately reflect existing local conditions.

Given this, Indiana — like many other states — opted to develop its own nutrient criteria. The Indiana Department of Environmental Management (IDEM) is working in cooperation with the U.S. EPA to develop a better understanding of nutrients in Indiana surface waters. IDEM is also actively working to address nutrient issues through existing programs.

Recent Protection Efforts

U.S. EPA set the drinking-water criteria at 10 mg/L nitrate as N and 1 mg/L nitrite as N for the protection of human health

U.S. EPA developed its nitrate criteria at levels intended primarily to protect against methemoglobinemia or “blue baby syndrome.” Other studies have linked nitrate and nitrite levels to adverse reproductive and developmental outcomes in animals and humans.

Aquatic-life criteria for the protection of aquatic organisms have also been developed for ammonia as nitrogen, which varies with pH, temperature, and the life-stage of an organism. However, these criteria are intended to protect biological communities from the toxic effects of ammonia as nitrogen and do not address effects resulting from increased nutrients in rivers and streams. Typically, nutrient concentrations must be extremely high to be toxic to biological communities, and such concentrations are rarely found in the environment. Exceptions are concentrations of ammonia associated with accidental discharges from wastewater-treatment facilities, combined-sewer overflows, or concentrated-animal feeding operations.

Four Indiana state agencies working together to provide public health information about blue-green algae in lakes

Algae are important to the productivity of a lake or water body. However, filamentous green algae and blue-green algae (cyanobacteria) – in concentrated amounts – can be linked to some adverse health effects. Some of the factors that promote cyanobacteria growth include sunlight, warm weather, low turbulence, phosphorus and nitrogen.

In 2010, IDEM began monitoring select lakes through a new blue-green algae (cyanobacteria) surveillance program at a number of Indiana Department of Natural Resources (IDNR) public access beaches. IDEM and IDNR coordinate on the monitoring, and the Indiana State Department of Health, and the Board of Animal Health manage the reporting of results to the public and issuing advisories when necessary.

The Indiana Nutrient Reduction Strategy

In 2016, Indiana developed a nutrient reduction strategy to help reduce nutrient loading to Indiana waters through point and non-point sources. The Indiana Nutrient Reduction Strategy represents the state’s commitment to assess the quality of its waters and to reduce nutrient runoff into surface waters.   The objectives of this strategy include:

  • Prioritization of watersheds for nutrient reduction efforts
  • The inventory and use of available resources to achieve their highest impact on nutrient reduction
  • Involving and engaging stakeholders in the state’s efforts to reduce nutrient loads
  • Regulatory control of point sources
  • Encouraging voluntary, incentive-based conservation through the many state and federal water quality related programs

Additional Resources

US. Environmental Protection Agency, 2000. Nutrient criteria technical guidance manual – Rivers and streams. Washington, D.C.: U.S. EPA Office of Water.  EPA-822-B00-002, 253 p.

Notes: This manual provides a good overview of the issue of eutrophication of streams and rivers and contains a section on regulations to date.

U.S. Environmental Protection Agency, 2000. Ambient water quality criteria recommendations -Information supporting the development of state and tribal nutrient criteria-Rivers and streams in Nutrient Ecoregion VI. Washington, D.C.: U.S. EPA Office of Water. EPA-822-B00-017.

Notes: This document provides a good overview of the issue of eutrophication of streams and rivers and describes potential plans for nutrient criteria development for a primary ecoregion in Indiana.