Toxic substances

Identification of toxic substances

Hazard assessment of toxic substances

Hormone (endocrine) disruption


Identification of toxic substances

Toxic substances, or groups of toxic substances, were identified on the basis of the level of concern expressed by the regulatory authorities and the statutory nature conservation agencies.

Toxic substances of concern to UK and European regulatory authorities appear on various lists of chemicals identified for priority action for their control. These lists include Lists I and II of the Dangerous Substances Directive, the Red List established by the North Sea Conferences and a priority list for substances contributing to diffuse pollution established by OSPAR. Details of these lists are provided in Appendix A. Table 4.3 summarises the toxic substances, or groups of substances, and indicates the source list for that substance.

The following toxic substances of concern were identified by the nature conservation agencies and these, together with most of those listed in Table 4.2, are dealt with in detail in Appendix B.


Other pesticides (e.g. synthetic pyrethroids)

Radioactive substances

Oils (in general)

Surfactants (in general)

Fish farming chemicals (in general)

Biocides used in disinfection (in general, covering chlorine and bromine)

Booster biocides

Phthalates (general)

Algal toxins

Microbial pathogens

Table - Toxic substances

Hazard assessment of toxic substances

A profile of each toxic contaminant, or group of contaminants, has been prepared providing information on the major sources, fate and behaviour in the marine environment, main biological effects and potential impact on interest features of European marine sites. These profiles are located in Appendix B.

The profiles have been compiled using information on each substance, or group of substances, already collated in major reviews, including those prepared by the World Health Organisation and, for those List II substances with EQSs, the report prepared by WRc for the derivation of the EQS (Grimwood and Dixon, 1997). Extensive literature reviews on each substance have not been carried out. The profiles, therefore, indicate the most sensitive groups of organisms but do not purport to summarise all of the available toxicity information for all groups of organisms. The most common groups of organisms used for toxicity testing are invertebrates, fish and, to a lesser extent, algae. Consequently, most of the toxicity information is available for these groups of organisms. Information for marine macrophytes, seabirds and sea mammals is not generally available in these reviews but has been included where such data exist.

The table linked above summarises the key features of the profile of each substance, or group of substances, and identifies the toxic effects on the main groups of marine organisms.

The standardised terms used in the table linked above for fate and behaviour, persistence, bioaccumulation and toxicity have been based on consistent criteria listed below.

Fate and behaviour




Details on criteria

In applying these criteria to the identified toxic substances, or groups of substances, there are cases where the required information is not available or has been estimated or where classifications have been borderline. The reader is urged to use the linked details only as an initial indication of the hazard posed by a substance and to consult the profile in Appendix B and, if necessary, the supporting literature referenced in the profile.

Hormone (endocrine) disruption

Information is available which suggests that some of the toxic substances considered in this Section may have endocrine modulating effects. The Environment Agency has recently undertaken a review of the scientific evidence on endocrine modulating substances in wildlife (Environment Agency 1998a). The Agency has also produced a consultative report on the potential controls of these substances which contains a straightforward explanation of the issues (Environment Agency 1998b). The former report makes a critical assessment of the evidence for endocrine disruption and its potential effects on the environment in England and Wales, and aims to establish a strategy for their management and control.. The report focuses on wildlife species and reported effects in laboratory and field investigations. However, they do recognise that the report can only be taken as an interim assessment of what is a rapidly developing issue. (The reader is referred to the Environment Agency publications for a detailed account of the mode and evidence of endocrine modulation).

The endocrine system is a complex internal system of hormone, secretory glands and receptors responsible for the growth, metabolism and reproduction both in plants and animals. Substances can interfere with the functioning of the endocrine system and have been shown to interfere with these processes. Such substances termed 'endocrine-disrupting' or 'endocrine-modulating' have emerged in recent years as a major issue of concern for the environment and human health.

Environmental monitoring programmes and research confirm that potential endocrine disrupting substances are being released into the environment. Most of these substances are under some regulatory control due to their toxicity and environmental quality standards already exist for the aquatic environment for some substances. What is not known is whether these standards adequately protect against endocrine-modulating effects.

An impairment of endocrine function can have far-reaching consequences and lead to clear biological effects as measured at the individual, population, community or even ecosystem level. The Agency (Environment Agency 1998a) has summarised substances currently implicated as having endocrine modulating properties in published literature, from in vitro screening assessments (tests on cultures of specially bred cell lines or tissue taken from living organisms) or from in vivo toxicological evaluations (tests on living animals). Of the synthetic substances considered in this guidance manual, the substances in Section have been identified as having some endocrine modulating effects. These effects have been characterised as:

  • oestrogenic - mimic the feminising effects in animals of the natural female sex hormones called oestrogens;
  • anti-oestrogenic - block the feminising effects of oestrogens;
  • anti-androgenic - block the masculinising effects of male sex hormones called androgens.

Extensive research is being conducted world-wide in order to provide more information on the potential effects of endocrine-modulating substances. However, the Agency has proposed (Environment Agency 1998a) a precautionary approach in addressing this issue. A dual approach has been proposed, in which the Agency will take a number of specific preventative actions, taking account of relative cost and benefits and, at the same time, continue to make its contribution to improving scientific understanding through research and development and environmental monitoring programmes.

Endocrine modulating substances identified

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