To the editor

The authors’ reply

“…Our thanks to Junghans et al for their letter, which raises a number of important issues in relation to our recent publication , relating principally to the differences in deriving water quality guidelines in Australia and New Zealand compared with the European Union and Switzerland. Specifically, Junghans et al challenge our references to the derivation of environmental quality standards for pharmaceuticals used in the European Union under the Water Framework Directive and in Switzerland under the Swiss Water Protection Ordinance. The process for deriving water quality guidelines in Australia and New Zealand is currently being revised; however, consistent with the approach adopted in 2000 , the preferred approach is to use chronic toxicity data in a species sensitivity distribution (SSD) using a Burr type III statistical fit.…”

“…The main point of contention is our use of the word “reliability.” In the Australian and New Zealand guidelines, it means something very specific, as defined above; and it was on that basis that we applied our classification to the European Union and Swiss data that used assessment factors. Junghans et al use “reliability” in a broader sense, referring to “the things we do not know about,” including laboratory to field extrapolations and the sensitivity of untested species.…”

Learned Discourse: Timely Scientific Opinions

“…Other fundamental differences among regulatory agencies will be difficult to reconcile because they reflect societal preferences. The EU Water Framework Directive (European Commission 2013) specifically allows the use of assessment factors to incorporate an additional level of precaution in situations where the level of evidence is not optimal, for example, when the prescribed number of species for using an SSD is not satisfied (Junghans et al 2016). Other jurisdictions suggest that applying additional assessment factors on top of what is considered to be an uncertain outcome will propagate uncertainty and result in unreliable standards that may be so low as to be difficult to measure using standard analytical techniques (Kumar et al 2016).…”

Chemical standard derivation for the protection of aquatic life: A guided world tour

“…Other fundamental differences among regulatory agencies will be difficult to reconcile because they reflect societal preferences. The EU Water Framework Directive (European Commission ) specifically allows the use of assessment factors to incorporate an additional level of precaution in situations where the level of evidence is not optimal, for example, when the prescribed number of species for using an SSD is not satisfied (Junghans et al ). Other jurisdictions suggest that applying additional assessment factors on top of what is considered to be an uncertain outcome will propagate uncertainty and result in unreliable standards that may be so low as to be difficult to measure using standard analytical techniques (Kumar et al ).…”