Chapter 13
Endocrine-Disrupting Chemicals in
Marine Environment
M. R. Preston
13.1
Introduction
The recognition that certain chemicals had oestrogenic activity dates back to the work
of Dodds and co-workers in the 1930S (Dodds and Lawson 1938; Dodds et al.1938). The
use of synthetic oestrogens in medicine began in the 1940S with the synthetic oestrogen diethylstilboestrol (DES) being widely used with the intention of preventing abortions and pregnancy complications in women. Its use was, however, largely counterproductive, and it was eventually found to increase abortions, neonatal deaths, premature births and a certain form of vaginal cancer (Herbst et al. 1971). The major use
of synthetic hormones since this time has been in the contraceptive pill in the form of
ethynyl derivatives of oestradiol.
During the 1990S, support began to grow for the hypothesis that a number of apparently unrelated changes within the environment and in human populations could
be related to exposure to environmental chemicals, which has lead to specific damage
to endocrine systems. Such changes included such 'classical' pollution problems as
eggshell thinning in top predator birds, imposex in molluscs and reproductive disorders in seals, and more recently discovered phenomena as varying degrees of intersex/hermaphrodite occurrence in fish, reptiles and mammals. In human populations,
incidences of a variety of cancers (particularly breast cancer) and disorders of the male
reproductive system such as declines in sperm counts, cryptorchidism and hypospadias all have potential origins with environmental chemicals.
The linking factor governing these effects is that they are all related (either totally
or in part) to problems within the endocrine system. Whilst there is now a growing
body of evidence to suggest that certain types of endocrine-disrupting behaviour can
be demonstrated by chemicals within the laboratory, only a few chemicals have been
conclusively shown to have such effects in the open environment. The best known is
probably the link between tributyltin compounds in antifouling paints and imposex
in molluscs. In many cases, links between environmental chemicals and other effects
remain fairly circumstantial, and a great deal of research effort is presently being placed
into finding evidence for or against such connections.
This chapter reviews the present evidence base for endocrine-disrupting effects and
extends beyond the marine environment into some discussion relating to human health
effects and environmental chemicals. IEH (1995), Hester and Harrison (1999) and Vos
et al. (2000) have recently published reviews of the topic, and the present work extends
some aspects of these publications and introduces some more recent findings. It is not
intended to be a monograph on the details of the endocrine system but rather a general review of the state of knowledge and uncertainty in the field.
Endocrine-Disrupting Chemicals in
Marine Environment
M. R. Preston
13.1
Introduction
The recognition that certain chemicals had oestrogenic activity dates back to the work
of Dodds and co-workers in the 1930S (Dodds and Lawson 1938; Dodds et al.1938). The
use of synthetic oestrogens in medicine began in the 1940S with the synthetic oestrogen diethylstilboestrol (DES) being widely used with the intention of preventing abortions and pregnancy complications in women. Its use was, however, largely counterproductive, and it was eventually found to increase abortions, neonatal deaths, premature births and a certain form of vaginal cancer (Herbst et al. 1971). The major use
of synthetic hormones since this time has been in the contraceptive pill in the form of
ethynyl derivatives of oestradiol.
During the 1990S, support began to grow for the hypothesis that a number of apparently unrelated changes within the environment and in human populations could
be related to exposure to environmental chemicals, which has lead to specific damage
to endocrine systems. Such changes included such 'classical' pollution problems as
eggshell thinning in top predator birds, imposex in molluscs and reproductive disorders in seals, and more recently discovered phenomena as varying degrees of intersex/hermaphrodite occurrence in fish, reptiles and mammals. In human populations,
incidences of a variety of cancers (particularly breast cancer) and disorders of the male
reproductive system such as declines in sperm counts, cryptorchidism and hypospadias all have potential origins with environmental chemicals.
The linking factor governing these effects is that they are all related (either totally
or in part) to problems within the endocrine system. Whilst there is now a growing
body of evidence to suggest that certain types of endocrine-disrupting behaviour can
be demonstrated by chemicals within the laboratory, only a few chemicals have been
conclusively shown to have such effects in the open environment. The best known is
probably the link between tributyltin compounds in antifouling paints and imposex
in molluscs. In many cases, links between environmental chemicals and other effects
remain fairly circumstantial, and a great deal of research effort is presently being placed
into finding evidence for or against such connections.
This chapter reviews the present evidence base for endocrine-disrupting effects and
extends beyond the marine environment into some discussion relating to human health
effects and environmental chemicals. IEH (1995), Hester and Harrison (1999) and Vos
et al. (2000) have recently published reviews of the topic, and the present work extends
some aspects of these publications and introduces some more recent findings. It is not
intended to be a monograph on the details of the endocrine system but rather a general review of the state of knowledge and uncertainty in the field.