Environmental Engineering Reference
In-Depth Information
3 indicate similar toxicity), 20% of degradates were more than three times
more toxic and some degradates (9%) were more than an order of magnitude
more toxic. In general, increases in toxicity from parent to degradate were
observed for parent compounds that had a low toxicity.
There are a number of possible explanations for these toxicity increases:
(1) the active moiety of the parent compound is still present in the degradate;
(2) the degradate is the active component of a pro-compound; (3) the biocon-
centration factor for the degradate is greater than the parent; and (4) the
transformation pathway results in a compound with a different and more
potent mode of action than the parent (Sinclair & Boxall
2003
).
Identification of future problem contaminants
While we now know a lot more about many emerging contaminants, we have
still only detected a small proportion of emerging contaminants that are likely to
occur in the environment and we have information on the ecotoxicological
effects of an even smaller number of these. It is probably timely, therefore, to
begin to tackle the issue of emerging contaminants in the environment in a more
systematic way than we are doing at present. In order to do this, we should begin
to work towards a better characterisation of (1) what emerging contaminants are
released to and formed in the environment; (2) the occurrence, fate and transport
of emerging contaminants in the environment; and (3) effects on organisms and
the implications in terms of ecosystem functioning. This information could then
be used to expand current monitoring programmes to quantify those emerging
contaminants that are likely to pose the greatest risk to environmental and
human health. The use of ecological monitoring, biomarker assessment and
effects directed analysis could also providevaluableinformation.Apotential
approach is outlined in
Fig. 5.2
and is described in more detail below.
Identifying inputs of emerging contaminants to the environment
A good first step in focusing work on emerging contaminants is to identify
what substances are being released to the environment and what substances
are being formed in the environment. This information is often very difficult to
obtain but can be extremely helpful in prioritising monitoring and testing
requirements, steering analytical method development and informing the
design of ecotoxicity studies. In the past, we have successfully used a range of
sources of information such as usage amounts and patterns, product compos-
ition data, usage surveys and life cycle analysis to evaluate the potential for
environmental exposure. Other approaches such as remote sensing may also
provide valuable information on potential pressures in a catchment. As a result
of REACh, our understanding of the use of chemicals in Europe will improve as
companies will be required to provide data on amounts used. Metabolites and
environmental transformation products are a special case as these are formed
