A weight‐of‐evidence approach for deriving a level of concern for atrazine that is protective of aquatic plant communities. (18th January 2017)

• Record Type: Journal Article
• Authors: Moore, Dwayne RJ; Greer, Colleen D; Manning, Gillian; Wooding, Katie; Beckett, Kerrie J; Brain, Richard A; Marshall, Gary
• Is Part Of: Integrated environmental assessment and management. Volume 13:Number 4(2017:Oct.)
• Page Start: 686
• Page End: 701
• Publication Date: 2017-01-18
• Subjects: Atrazine -- Level of concern -- Mesocosm -- Aquatic plants; Environmental management -- Periodicals; Pollution -- Periodicals; Environmental toxicology -- Periodicals; Environmental risk assessment -- Periodicals; Environmental impact analysis -- Periodicals; 628
• DOI: 10.1002/ieam.1865
• Languages: English
• ISSNs: 1551-3777

Abstract

ABSTRACT: Atrazine is a selective triazine herbicide widely used in the United States primarily for control of broadleaf weeds in corn and sorghum. In 2003, the US Environmental Protection Agency (USEPA) concluded that atrazine poses potential risks to sensitive aquatic species. Consequently, a surface water monitoring program was developed to assess whether measured levels of atrazine could impact aquatic plants in vulnerable watersheds. To facilitate evaluation of the monitoring data, the Agency needed to establish a level of concern (LOC) below which atrazine would not cause unacceptable adverse effects to aquatic plant communities. Several attempts at developing a community‐level LOC have followed from USEPA but none have been formally accepted or endorsed by independent Scientific Advisory Panels. As part of registration review, the USEPA needs to revisit development of a community‐level LOC for atrazine that will be protective of aquatic plant communities. This article reviews 4 methods that can or have been used for this purpose. Collectively, the methods take advantage of the large number of single species and mesocosm studies that have been conducted for aquatic plants exposed to atrazine. The Plant Assemblage Toxicity Index (PATI) and the Comprehensive Aquatic Systems Model for atrazine (CASMATZ2 ) incorporate single‐species toxicity data but are calibrated with micro‐ and mesocosm study results to calculate community‐level LOCs. The Brock et al. scoring system relies exclusively on mesocosm studies. Single‐species toxicity data were used in a modified version of the USEPA's Water Quality Criteria (WQC) method. The 60‐day LOCs calculated using the 4 methods ranged from 19.6 to 26 µg/L. A weight‐of‐evidence assessment indicated that the CASMATZ2 method was the most environmentally relevant and statistically reliable method. Using all 4 methods with weights based on method reliability, the weighted 60‐day LOC was 23.6 µg/L. Integr Environ Assess Manag 2017;13:686–701. © 2016 SETAC Key Points: A level of concern (LOC) that is protective of aquatic plant communities is required for atrazine by the USEPA to interpret monitoring data and for decision making. The USEPA has not been successful in developing such an LOC. We evaluated 4 methods for deriving an atrazine LOC, each having strengths and weaknesses. Using the results of our weight‐of‐evidence evaluation of available methods, we developed an LOC of 23.6 µg/L for atrazine protective of aquatic plant communities.