The newer multisubstance-Potentially Affected Fraction (ms-PAF) method has been developed so it can measure the impact of all pesticides in a mixture, regardless of whether they affect organisms in different ways (e.g. this method can account for chemicals that impact cell division and chemicals that impact photosynthesis).

The ms-PAF method estimates the ecological risk of a chemical on an aquatic ecosystem by determining the percentage of species that would potentially be affected by a given concentration of a pesticide. When multiple pesticides are detected, the percentage of species affected by the pesticides are added together. Currently, in freshwater and estuarine systems only herbicides that impact on photosynthesis are reported using the ms-PAF method. For these herbicides only species that photosynthesise (such as micro-algae and seagrasses) are used to assess the potential impact of these herbicides, as these are the most sensitive group of organisms to these herbicides. As our understanding of the toxicity of other pesticides expands, these pesticides will progressively be included in reporting.

The 2017 report card reports on thirteen herbicides that impact photosynthesis (ametryn, atrazine, diuron, hexazinone, tebuthiuron, bromacil, fluometuron, metribuzin, prometryn, propazine, simazine, terbuthylazine, terbutryn).

In future report cards, ms-PAF will assess up to 28 of the pesticides detected in the Region, including herbicides, insecticides and fungicides.

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