disrupting chemicals (EDCs).
A policy report from The
full text of the report is available on-line as an Adobe Acrobat
coverage in Nature
Royal Society's report concludes with very cautious statements about
the potential impacts of EDCs on humans, emphasizing the lack of
data and the uncertainty about causation. It cites "strong
evidence" linking EDCs to effects in wildlife. Despite the
scientific caution, it takes a strong precautionary stance, recommending
continued research, acknowledging that some of the public concerns
about human impacts "already have some foundation" and
suggesting that exposures, especially to pregnant women, be minimized.
"Regulations cannot be 'put on hold' until all the evidence
has been collected."
report resembles the US National Academy of Sciences
assessment in acknowledging that very few studies ("if
any") have attempted to look for causal links between EDCs
and reproductive effects in people. Hence the fact that there is
no confirmation is a reflection of ignorance rather than one of
safety. It differs from the NAS report, however, in that it takes
a far more precautionary stance about recommended policies.
The report states "It is preferable to establish the likely
effects of EDCs on organisms in the environment in order to prevent
damage, rather than wait until the damage has occurred and then
try to establish the cause."
report's main weakness is that it avoids the issue of low-dose
impact. This allows it to conclude that EDCs are unlikely
to cause many human effects at common levels of exposure, although
the report qualifies that strongly by observing that only a limited
number of compounds have been studied. It argues that because most
identified EDCs in the environment have weak hormonal activity,
human exposure would have to be high to cause effects. This gap
in the report is perhaps understandable because of debates
over whether some of the key low dose studies could be replicated.
This was resolved affirmatively early during 2000, with published
replication of Fred vom Saal's research. By this time, the Royal
Society's report was most likely already in print.
points from the report's summary:
are exposed daily to chemicals that have been shown, or suggested,
to have hormone-disrupting properties. Speculation has linked
this to a range of disorders. Whilst high levels of exposure to
some EDCs could theoretically increase the risk of such disorders,
no direct evidence is available at present. Trends in the incidence
of some of these disorders are difficult to discern and when found,
are difficult to interpret because of inconsistencies in method.
EDCs are but one of a variety of potential risk factors, both
environmental and genetic. Despite the uncertainty, it is prudent
to minimize exposure of humans, especially pregnant women, to
regard to EDCs in the environment, firm assessment of the risk
to humans is not possible because of a lack of relevant data about
the effects of EDC exposure. On the basis of limited anaimal data,
identified environmental EDCs appear to pose minimal risk to humans
on their own, but the risk from mixtures of compounds is unknown."
the lack of information on the effect on humans of EDCs in the
environment, strong evidence links EDC exposure to effects on
some organisms in the environment." ... "The action
of EDCs has resulted in the localised destruction of certain species
and is a cause for grave concern."
effort should be focused on the identification of potential EDCs
and the assessment of risk posed by individual chemicals, or by
combinations of chemicals, supported by vigorous epidemiological
the issue of EDCs is confused by serious gaps in our knowledge,
policies to deal with the current concerns must be developed,"
... "hand in hand with ongoing research."
tests which will detect the endocrine-disrupting activities of chemicals
are necessary," particularly to deal with "abnormalities
of sexual differentiation/reproductive development where cause and
consequence may be separated by a considerable period of time."
reality, humans are exposed not to a single endocrine disrupter
but to a 'cocktail'
of such chemicals, and the possibility that such chemicals have
additive or reinforcing effects (e.g., combination of an oestrogenic
with an anti-androgenic compound) has to be considered seriously.
Using standard animal tests (acute toxicity tests) to evaluate these
effects would be an extremely complex task with many potential problems."
report has a good summary of the effects of tributyltin (TBT) on
It observes that these effects "were completely unexpected
and unpredicted, despite legislation governinng new chemicals; nobody
foresaw that TBT would cause endocrine disruption in molluscs."
... "This suggests that, until our understanding of how,
and what, chemicals cause endocrine disruption improves very considerably,
it is likely that other unexpected cases of endocrine disruption
in wildlife will become apparent. This example also highlights
the difficulty of predicting what effects a chemical will have in
the wider environment where it may mix with other chemicals, get
degraded, or come into contact with a variety of species of animals