There is growing evidence of falling sperm counts, an increase in the
incidence of testicular cancer, and increase in the numbers of boys being
born with abnormalities of their reproductive system. It has been speculated
that these phenomena have been caused by endocrine disrupters - substances
mimicking oestrogens or acting in other ways. This is discussed with special
reference to environmental health and occupational hygiene implications.
Summary overview of the evidence:
Thus in laboratory experiments many chemicals are oestrogenic, for
DDT & other organochlorine pesticides
PCBs, Dioxins & Dibenzofurans
Others (including ‘natural’ weak dietary oestrogenic agents)
Changes in aquatic life have been observed observed (? because of oestrogenic
Sex ratio changes
However there are problems with a large part of the evidence (positive
or negative). These include bias
chance, and confounding. It should be borne in mind that adverse effects
on reproduction can arise through exposures other than endocrine disruption,
for example through thermal effects, psychological stress and other effects
e.g. of a directly toxic non-endocrine type.
Possible causal agents and mechanisms:
There is considerable speculation regarding the causal agents, mechanisms
and the time course over which they operate.
Some foods, such as soya but also various cereals, man may contain weak
but abundant phyto-oestrogens.
Medical therapeutic agents e.g the contraceptive pill or its metabolites
Many chemicals of industrial origin have been implicated – and the risks
associated with exposure to these substances need to be assessed both because
of the potential consequences for the workforce, and for the wider community.
There are a few well substantiated reports of male infertility resulting
from specific occupational exposures. Many of the suspect endocrine disrupters
are ubiquitous in industry, with functions ranging from plasticisers to
pesticides. Their chemical identities are also diverse, ranging from phthalates
to to bisphenols to halogenated hydrocarbons (such as dibromochloropropane
DBCP, or polychlorinated hydrocarbons such as PCBs). It should be noted
that other exposures, such as to lead, may have
effects on reproduction.
Evidence in an Occupational Context:
There is a range of evidence of limited quality that occupational exposures
might affect male reproductive health e.g: disease/ill-health: infertility,
tumours etc (not all due to endocrine disruption) and evidence of biological
effect - not necessarily disease.
Though not necessarily through Endocrine Disruption can result from:
Lead Pb, Mercury Hg, Cadmium Cd, other inorganics
Dibromochloropropane DBCP (a nematocide), other organics
Various categories of employment may need more focussed investigation
because of routine data collection suggesting low Standardised Fertility
Ratios (OPCS) eg laboratory technicians, cable jointers
The numbers, morphology or motility of sperm cells have been shown to be
possibly affected (with evidence of varying quality) in associtaion with
exposures such as:
organophosphates, other pesticides
glycol ethers, other solvents
Other techniques (hormone measurements: Testosterone, FSH, LH) have indicated
a possible consequence of occupational exposure to agents such as the fungicide
Occupational Hygiene Implications
There is a need for further research:
Extent of human exposure and uptake
Case-Control studies of Infertility
Retrospective studies e.g.:
Cohort studies of Semen Quality
Prospective studies e.g.:
There is also a need for more awareness in practice:
Identify putative exposure
Identify, report and investigate possible health effects
Communicate, inform and debate - especially re the ‘Precautionary Principle’
Hence apply agreed level of control
There is evidence of trends with time of an increased frequency of
male tumours, malformations and other anomalies and decline in semen quality.
This is complemented by laboratory experiments, clinical & biological
observations. However the quality of a great deal of the evidence is still
limited and especially patchy in an occupational context.
More research is needed in order to assess the risks associated with
these exposures. Epidemiologic studies in progress are using birth cohorts
or case-control methods in attempts to answer important questions of causality.
For example the author is a co-investigator in a study on male
reproductive health in a Scottish birth cohort. However systematic
industry based approaches are also needed in order to help assess the risks,
and subsequently to reduce the likelihood of harm through reduction of
More debate and consensus on precautionary principles is probably needed.
Internet Links related to endocrine disrupters: