Julia E. Norman

Health-Based Screening Levels to Evaluate U.S. Geological Survey Ground water Quality Data

Federal and state drinking-water standards and guidelines do not exist for many contaminants analyzed by the U.S. Geological Surveys National Water-Quality Assessment Program, limiting the ability to evaluate the potential human-health relevance of water-quality findings. Health-based screening levels (HBSLs) were developed collaboratively to supplement existing drinking-water standards and guidelines as part of a six-year, multi-agency pilot study. The pilot study focused on ground water samples collected prior to treatment or blending in areas of New Jersey where groundwater is the principal source of drinking water. This article describes how HBSLs were developed and demonstrates the use of HBSLs as a tool for evaluating water-quality data in a human-health context. HBSLs were calculated using standard U.S. Environmental Protection Agency (USEPA) methodologies and toxicity information. New HBSLs were calculated for 12 of 32 contaminants without existing USEPA drinking-water standards or guidelines, increasing the number of unregulated contaminants (those without maximum contaminant levels (MCLs)) with human-health benchmarks. Concentrations of 70 of the 78 detected contaminants with human-health benchmarks were less than MCLs or HBSLs, including all 12 contaminants with new HBSLs, suggesting that most contaminant concentrations were not of potential human-health concern. HBSLs were applied to a state-scale groundwater data set in this study, but HBSLs also may be applied to regional and national evaluations of water-quality data. HBSLs fulfill a critical need for federal, state, and local agencies, water utilities, and others who seek tools for evaluating the occurrence of contaminants without drinking-water standards or guidelines.

Mixtures of dissolved pesticides in 100 streams in the Midwestern U.S., 2013

Dissolved pesticides were measured in weekly water samples from 100 freshwater streams across eleven states in the Midwestern U.S. during May-August, 2013. A total of 182 pesticide compounds (94 pesticides and 88 degradates) were detected, with a median of 25 compounds detected per sample and 54 detected per site. Potential aquatic toxicity was evaluated using the Pesticide Toxicity Index and by comparison to U.S. Environmental Protection Agency aquatic-life benchmarks. In a screening-level assessment, about 5% of streams were predicted to have potential effects on fish and 58% potential effects on invertebrates. In 75% of streams, short-term effects on algal growth were predicted, with potential for longer-term effects on algal communities predicted in 9% of streams. A relatively small number of pesticides the herbicides atrazine, acetochlor, and metolachlor, the insecticides imidacloprid, fipronil, and organophosphate (OP) insecticides, and to a lesser extent, the fungicide/degradate carbendazim were predicted to be the largest contributors to potential toxicity of pesticide mixtures. This data release provides pesticide compound concentrations, watershed characteristics, and aquatic-life benchmarks used in the analysis presented in the journal article, Pesticide mixtures and potential aquatic toxicity in a synoptic study of Midwestern U.S. streams, May-August, 2013, by Nowell, L.H., Norman, J.E., Moran, P.W., Schmidt, T., Mahler, B., Nakagaki, N., Van Metre, P.C., Shoda, M.E., Stone, W.W.

Corrigendum to “Pesticide Toxicity Index—A tool for assessing potential toxicity of pesticide mixtures to freshwater aquatic organisms” [Sci. Total Environ. 476–477 (2014) 144–157]

https://doi.org/10.1016/j.scitotenv.2013.12.088 Refers to: L.H. Nowell, J.E. Norman, P.W. Moran, J.D. Martin, W.W. Stone. Pesticide Toxicity Index—A tool for assessing potential toxicity of pesticide mixtures to freshwater aquatic organisms. Science of the Total Environment, Volume 476–477, 1 April 2014, Pages 144–157. The authors regret that in the above published article, an error appeared in one sentence of the text and is corrected below. In Section