School of Biological Sciences
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School of Biological Sciences |
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Environmental Pollution and Toxicology |
A lecture by Dr Rick Leah
(brief Lecture notes/overheads are available here
addnl notes on Env Agency Policy Dev here )
Environmentalists are increasingly concerned that pre-approval testing of chemicals, including pesticides, insufficiently addresses potential toxicity of these substances to the endocrine system of mammals. Unease arises from evidence in humans of decreasing sperm counts in men, and increases in birth defects and cancers affecting reproductive organs. Effects on wildlife provide evidence that hormonally-active compounds are present in the environment at biologically significant concentrations.
One phenomenon which has led to most interest is that of intersex fish. These are essentially male fish which show varying degrees of feminisation including testes containing eggs and blood containing a female protein, Vitellogenin. These effects are known to occur in fish living in the Mersey Estuary (see the EDMAR Report referenced below) but not in those living in clean rivers such as the Welsh Dee. Although the cause of ED in such estuarine fish remains obscure, the phenomenon was first observed in roach (Rutilus rutilus) living in sewage ponds emptying into the River Thames. The cause of this has been identified as excreted human hormones and other oestrogens being re-activated as they pass through sewage works or by detergent breakdown products (alkylphenols ).
The Environment Agency is now satisfied that it has identified the main ways these substances enter the UK freshwater environment and is working on the best ways of reducing their impact. The EA policy can be summarised as:
implementing pollution reduction programmes specific to each substance;
developing and implementing environmental quality standards (EQSs) or targets for steroids and alkylphenols (these are concentrations below which animals are not affected);
encouraging industry to implement voluntary reduction measures where these substances are used
targeting pollution prevention work at reducing releases at source (through the Integrated Pollution Prevention and Control system);
carrying out collaborative research in high risk catchments to investigate options for reducing inputs of these substances.
The Agency will target areas most at risk. For example, an initial assessment of rivers most at risk from low dilution of sewage works effluents has already been carried out.
Many of the Endocrine disrupting effects (but by no means all) that have been
observed in the environment are due to oestrogenic chemicals so these have been
the focus for most investigation and regulation. A lot of this type of work has
been done using a genetically modified yeast which has had the human oestrogen
receptor inserted into its genome. Notes on the the Yeast Assay for Oestrogenic chemicals
are available here
The EDMAR project was a recent investigation of the
phenomenon of Endocrine Disruption in fish in Estuaries in which the University
of Liverpool played a small part. The EDMAR Report is now available on-line (although it is
5MB in size). However, the Executive summary may be enough explanation for many
http://www.defra.gov.uk/environment/chemicals/hormone/report.htm
For the last few years, it has been difficult to determine how extensive the
problem of ED is as an environmental problem. See the more detailed page of
discussion for further info on how the debate is progressing.
Environment Agency – summary of impact on fish
Article: No
going back on sex change fish
There is a very extensive report (broken down into a number
of chapters that contain very useful information) on the recent (2002) Global Assessment
of the science background to Endocrine Disruption (see the Exec Summary for a
digestible summary but look at the other chapters for case studies etc.)
(prepared by International
Programme on Chemical Safety (supported by WHO & UNEP)
http://www.who.int/ipcs/publications/new_issues/endocrine_disruptors/en/