310
M. R. Preston
13.2
Definition of Endocrine-Disrupting Chemicals
A considerable number of terms have been used to describe the chemicals that fall
within the general category of endocrine-disrupting chemicals, which have largely
reflected different aspects of their behaviour as understood at particular times. The
terms include oestrogen mimics, oestrogenic chemicals, anti-oestrogens, environmental oestrogens, endocrine moderators, eco-oestrogens, xeno-oestrogens, anti-androgens, hormone-related toxicants, and probably other terms. More recently, the term
'endocrine disrupter' has become favoured, because it allows effects arising from
changes in any part of the endocrine system including thyroid, thymic and pituitary
hormones (Hester and Harrison 1999).
However, there are still a variety of definitions of endocrine-disrupting chemicals
that are given in the literature, and some of these are given in Table 13.1 below. The
complexity of these definitions reflects two problems. The first problem involves the
difficulty in defining what is meant by 'adverse' in this context (i.e. how far outside the
normal range of responses is adverse?). The second problem involves the need to distinguish between direct interference with endocrine systems and those caused as a
secondary consequence of toxic effects manifest elsewhere within metabolic systems.
13.3
The Effects of Endocrine-Disrupting Chemicals in Invertebrates
13.3.1
General Effects Excluding Imposex
A considerable number of both inorganic and organic chemicals have been shown to
cause endocrine-disrupting effects in invertebrates (Table 13.2).
The concentrations of endocrine-disrupting chemicals capable of causing such effects are low. For example, Billinghurst et al. (2000) found increased (doubled) cypris
major protein concentrations in naupilus stage larvae of the barnacle Balanus
amphitrite at concentrations of 1 Jlg rlof 4-n-nonyl phenol and 17f3-oestradiol. The
range of effects noted in invertebrates is considerable, and examples are given in
Table 13.3
13.3.2
Imposex
By far, the most widely studied aspect of the impact of endocrine-disrupting chemicals on invertebrates has been the phenomenon of ' impose x: Imposex is the chemically induced development of the physical characteristics of the opposite sex. The best
example of this is the development of a penis and vas deferens in females of the
dogwhelk Nucella lapillus as a result of exposure to the antifouling paint ingredient
tributyltin (TBT) used on ships, boats and harbour equipment. This effect is widespread, and approximately 72 spp and 49 genera of prosobranchs are affected worldwide (Pinder and Pottinger cited in Depledge and Billinghurst 1999). The sensitivity
of the organism to TBT varies considerably between species, but effects in N. lapillus
M. R. Preston
13.2
Definition of Endocrine-Disrupting Chemicals
A considerable number of terms have been used to describe the chemicals that fall
within the general category of endocrine-disrupting chemicals, which have largely
reflected different aspects of their behaviour as understood at particular times. The
terms include oestrogen mimics, oestrogenic chemicals, anti-oestrogens, environmental oestrogens, endocrine moderators, eco-oestrogens, xeno-oestrogens, anti-androgens, hormone-related toxicants, and probably other terms. More recently, the term
'endocrine disrupter' has become favoured, because it allows effects arising from
changes in any part of the endocrine system including thyroid, thymic and pituitary
hormones (Hester and Harrison 1999).
However, there are still a variety of definitions of endocrine-disrupting chemicals
that are given in the literature, and some of these are given in Table 13.1 below. The
complexity of these definitions reflects two problems. The first problem involves the
difficulty in defining what is meant by 'adverse' in this context (i.e. how far outside the
normal range of responses is adverse?). The second problem involves the need to distinguish between direct interference with endocrine systems and those caused as a
secondary consequence of toxic effects manifest elsewhere within metabolic systems.
13.3
The Effects of Endocrine-Disrupting Chemicals in Invertebrates
13.3.1
General Effects Excluding Imposex
A considerable number of both inorganic and organic chemicals have been shown to
cause endocrine-disrupting effects in invertebrates (Table 13.2).
The concentrations of endocrine-disrupting chemicals capable of causing such effects are low. For example, Billinghurst et al. (2000) found increased (doubled) cypris
major protein concentrations in naupilus stage larvae of the barnacle Balanus
amphitrite at concentrations of 1 Jlg rlof 4-n-nonyl phenol and 17f3-oestradiol. The
range of effects noted in invertebrates is considerable, and examples are given in
Table 13.3
13.3.2
Imposex
By far, the most widely studied aspect of the impact of endocrine-disrupting chemicals on invertebrates has been the phenomenon of ' impose x: Imposex is the chemically induced development of the physical characteristics of the opposite sex. The best
example of this is the development of a penis and vas deferens in females of the
dogwhelk Nucella lapillus as a result of exposure to the antifouling paint ingredient
tributyltin (TBT) used on ships, boats and harbour equipment. This effect is widespread, and approximately 72 spp and 49 genera of prosobranchs are affected worldwide (Pinder and Pottinger cited in Depledge and Billinghurst 1999). The sensitivity
of the organism to TBT varies considerably between species, but effects in N. lapillus