The Read-Across
Hypothesis and Environmental Risk
Assessment of Pharmaceuticals
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Abstract
Pharmaceuticals in
the environment have received increased attention
over the past decade, as they are ubiquitous in rivers and waterways.
Concentrations are in sub-ng to low μg/L, well below acute toxic
levels, but there are uncertainties regarding the effects of chronic
exposures and there is a need to prioritise which pharmaceuticals
may be of concern. The read-across hypothesis stipulates that a drug
will have an effect in non-target organisms only if the molecular
targets such as receptors and enzymes have been conserved, resulting
in a (specific) pharmacological effect only if plasma concentrations
are similar to human therapeutic concentrations. If this holds true
for different classes of pharmaceuticals, it should be possible to
predict the potential environmental impact from information obtained
during the drug development process. This paper critically reviews
the evidence for read-across, and finds that few studies include plasma
concentrations and mode of action based effects. Thus, despite a large
number of apparently relevant papers and a general acceptance of the
hypothesis, there is an absence of documented evidence. There is a
need for large-scale studies to generate robust data for testing the
read-across hypothesis and developing predictive models, the only
feasible approach to protecting the environment