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

Rachael A Smith; Michael St J Warne; Kerrie Mengersen; Ryan Dr Turner

doi:10.1002/ieam.1860

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

Integr Environ Assess Manag. 2017 Jul;13(4):754-764. doi: 10.1002/ieam.1860. Epub 2016 Dec 4.

Authors

Rachael A Smith^{1

2

3}, Michael St J Warne^{1

2

4

5}, Kerrie Mengersen³, Ryan Dr Turner^{1

2

3}

Affiliations

¹ Water Quality and Investigations, Science Division, Department of Science, Information Technology and Innovation, Queensland, Australia.
² Australian Rivers Institute, Griffith University, Nathan, Queensland, Australia.
³ Science and Engineering Faculty, Queensland University of Technology, Brisbane, Queensland, Australia.
⁴ National Research Centre for Environmental Toxicology, University of Queensland, Coopers Plains, Queensland, Australia.
⁵ Centre for Agroecology, Water and Resilience, Coventry University, Coventry, United Kingdom.

PMID: 27775206
DOI: 10.1002/ieam.1860

Abstract

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.

Keywords: Great Barrier Reef; Photosystem II herbicides; Pollutant loads; Relative-potency; Toxic equivalency factor.

MeSH terms

Coral Reefs*
Environmental Monitoring / methods*
Queensland
Toxicity Tests / methods*
Water Pollutants, Chemical / analysis
Water Pollutants, Chemical / toxicity*

Substances

Water Pollutants, Chemical