An improved method for calculating toxicity‐based pollutant loads: Part 2. Application to contaminants discharged to the Great Barrier Reef, Queensland, Australia

Pollutant loads are widely used to set pollution reduction targets and assess regulatory compliance for the protection of receiving waterbodies. However, when a pollutant load consists of a mixture of chemicals, reducing the overall load (mass) will not necessarily reduce the toxicity by a similar amount. This can be overcome by setting targets based on toxicity‐based loads (toxic loads, TLs), where the load is modified according to the relative toxicity (expressed as toxic equivalency factors [TEFs]) of each toxicant. Here, we present the second article of a 2‐part series in which a case study is used to demonstrate the application of the toxic load method proposed in Part 1. The toxic load method converts a pollutant load, comprised of multiple chemicals, to a toxic load, using a modified TEF approach. The modified approach uses a cumulative distribution of relative potency (ReP) estimates of multiple species to determine a TEF. It further improves upon previously published methods by including two tests to select the optimal percentile of the ReP distribution to determine the TEF. The first test is a test for environmental relevance that compares results against an independent mixture method, identifying the percentile that produces the most environmentally relevant TEFs and TLs. The second is a test for robustness which ensures the results are independent of the ReP of the selected reference chemical. Here, the TL method is applied to mixtures of pesticides that are discharged from agricultural land to the Great Barrier Reef (GBR) to test its utility. In this case study, the most environmentally relevant and robust TLs were generated using the 75th percentile of the ReP cumulative distribution. The results demonstrate that it is essential to develop pollution reduction targets based on toxic loads and making progress to meeting them will lead to a commensurate reduction in toxic effects caused by toxicants in waters of the GBR. Integr Environ Assess Manag 2017;13:754–764. © 2016 SETAC

[1]  S. Simpson,et al.  Total suspended solids, nutrient and pesticide loads (2015–2016) for rivers that discharge to the Great Barrier Reef – Great Barrier Reef Catchment Loads Monitoring Program. , 2018 .

[2]  Kerrie Mengersen,et al.  An improved method for calculating toxicity‐based pollutant loads: Part 1. Method development , 2017, Integrated environmental assessment and management.

[3]  J. Brodie,et al.  Reef Water Quality Protection Plan 2013. Prioritisation project report , 2014 .

[4]  Christopher W. Hickey,et al.  Revised Method for Deriving Australian and New Zealand Water Quality Guideline Values for Toxicants , 2014 .

[5]  Catherine J. Collier,et al.  Phytotoxicity of Four Photosystem II Herbicides to Tropical Seagrasses , 2013, PloS one.

[6]  Jochen F. Mueller,et al.  Pesticide monitoring in inshore waters of the Great Barrier Reef using both time-integrated and event monitoring techniques (2011 - 2012) , 2012 .

[7]  E. Copeland.  Choosing “The Best” , 2012 .

[8]  Britta Schaffelke,et al.  Assessing the additive risks of PSII herbicide exposure to the Great Barrier Reef. , 2012, Marine pollution bulletin.

[9]  S. Vardy,et al.  Large-scale pesticide monitoring across Great Barrier Reef catchments--Paddock to Reef Integrated Monitoring, Modelling and Reporting Program. , 2012, Marine pollution bulletin.

[10]  S. Uthicke,et al.  Herbicides increase the vulnerability of corals to rising sea surface temperature , 2011 .

[11]  Kirsten Heimann,et al.  Additive toxicity of herbicide mixtures and comparative sensitivity of tropical benthic microalgae. , 2010, Marine pollution bulletin.

[12]  K. Heimann,et al.  Comparative effects of herbicides on photosynthesis and growth of tropical estuarine microalgae. , 2008, Marine pollution bulletin.

[13]  T. Koontz,et al.  Reducing Nonpoint Source Pollution Through Collaboration: Policies and Programs Across the U.S. States , 2008, Environmental management.

[14]  O. Hoegh‐Guldberg,et al.  Synthesis of evidence to support the scientific consensus statement on the water quality in the Great Barrier Reef , 2008 .

[15]  D Raha,et al.  Paradigm shift in water environment protection in New South Wales , 2007 .

[16]  C. Tohyama,et al.  The 2005 World Health Organization reevaluation of human and Mammalian toxic equivalency factors for dioxins and dioxin-like compounds. , 2006, Toxicological sciences : an official journal of the Society of Toxicology.

[17]  Steave H Su,et al.  Development of a refined database of mammalian relative potency estimates for dioxin-like compounds. , 2006, Toxicological sciences : an official journal of the Society of Toxicology.

[18]  Michael St J Warne,et al.  Evaluation of Criteria Used to Assess the Quality of Aquatic Toxicity Data , 2005, Integrated environmental assessment and management.

[19]  Ross Jones.  The ecotoxicological effects of Photosystem II herbicides on corals. , 2005, Marine pollution bulletin.

[20]  P. Gramatica,et al.  Joint algal toxicity of phenylurea herbicides is equally predictable by concentration addition and independent action , 2004, Environmental toxicology and chemistry.

[21]  A. Kerswell,et al.  PHYTOTOXICITY OF PHOTOSYSTEM II (PSII) HERBICIDES TO CORAL , 2003 .

[22]  Michael J. DeVito,et al.  Framework for application of the toxicity equivalence methodology for polychlorinated dioxins, furans and biphenyls in ecological risk assessment , 2003 .

[23]  Mark Crane,et al.  Freshwater to saltwater toxicity extrapolation using species sensitivity distributions , 2002, Environmental toxicology and chemistry.

[24]  Timo Hamers,et al.  The potentially affected fraction as a measure of ecological risk , 2002 .

[25]  P. Gramatica,et al.  Predicting the joint algal toxicity of multi-component s-triazine mixtures at low-effect concentrations of individual toxicants. , 2001, Aquatic toxicology.

[26]  D. Morritt,et al.  Can saltwater toxicity be predicted from freshwater data? , 2001, Marine pollution bulletin.

[27]  D. Haynes,et al.  Water quality in the Great Barrier Reef World Heritage Area: past perspectives, current issues and new research directions. , 2000 .

[28]  S. Safe,et al.  Hazard and risk assessment of chemical mixtures using the toxic equivalency factor approach. , 1998, Environmental health perspectives.

[29]  T. Hutchinson,et al.  Analysis of the ecetoc aquatic toxicity (EAT) database IV — Comparative toxicity of chemical substances to freshwater versus saltwater organisms , 1998 .