Ambient Aquatic Life Water Quality Criteria for Atrazine - Revised Draft Fact Sheet
EPA has released and requested scientific views on a revised draft ambient water quality criteria document for atrazine. We developed acute and chronic criteria recommendations for atrazine designed to protect aquatic life in both freshwater and saltwater. At the same time, EPA released its revised Ecological Fate and Effects Risk Assessment for atrazine. Both documents incorporate our responses to additional information that became available after we published the earlier draft criteria atrazine water quality criteria document.
Atrazine is an herbicide used throughout the U.S. to control weeds in agricultural crops. It is moderately volatile, soluble in water, and resistant to natural degradation in water. Because of its chemical properties and widespread use as an herbicide, concerns have been raised over the risks it poses for both freshwater and saltwater organisms.
On September 26, 2001, the Agency published a draft criteria document and requested scientific views and information. EPA then extended the period for scientific information to close on Janaury 25, 2002, to allow all interested parties the opportunity to submit scientific views. The revised draft criteria document reflects the results of our consideration of the additional information that became available on scientific issues related to deriving the atrazine criteria and on the risk assessment methods we used.
The revised draft ambient water quality criteria document for atrazine contains ambient water quality criteria designed to protect aquatic organisms and their uses. Once final, these criteria are guidance for states and tribes and, in themselves, have no binding legal effect. However, they may form the basis for state water quality standards and become enforceable through NPDES permits or other environmental programs. These new draft atrazine criteria are published pursuant to Section 304(a) of the Clean Water Act (CWA).
What are the Revised Draft Atrazine Criteria Concentrations?
Freshwater Aquatic Life:
Except possibly where a locally important species is very sensitive, freshwater aquatic life and their uses should not be affected unacceptably if the one-hour average concentration of atrazine does not exceed 1,500 µg/L more than once every three years on the average (acute criterion) and if the Average Primary Producer Steinhaus Similarity deviation for a site is less than 5% (as determined using Comprehensive Aquatic Systems Model (CASM) or other appropriate model and index) and is not exceeded more than once every three years (or other appropriate return frequency sufficient to allow system recovery). The 5% index for the protection of aquatic plant community should also be protective of most freshwater animals (chronic criterion).
Saltwater Aquatic Life:
Except possibly where a locally important species is very sensitive, saltwater aquatic life and their uses should not be affected unacceptably if the one-hour average concentration of atrazine does not exceed 760 µg/L more than once every three years on the average (acute criterion) and if the thirty-day average concentration of atrazine does not exceed 17 µg/L more than once every three years on the average (chronic criterion).
How are the Revised Criteria in today's publication different from the 2001 Criteria?
The revised criteria in today's publication incorporate information on the toxicity of atrazine to aquatic plants and invertebrates that had not been available at the time of the 2001 publication. The change in critical endpoints reflects the scientific views received from the public.