Some synthetic chemicals can cause
reproductive problems in birds—a connection established as long ago as 1962(1).
An important scientific consensus that such effects may be caused by endocrine
disruption, and may have profound effects on bird population levels was the
direct result of a multidisciplinary conference organized by WWF US Senior
Scientist, Dr. Theo Colborn—who synthesised wildlife research for Great
Lakes, Great Legacy?(2), in 1991. The endocrine system controls development
and reproduction, through hormones (chemical messengers)(3). This
groundbreaking conference and the others that followed, called
'Wingspread'(4), after the conference venue, convened work sessions of
scientists representing a wide range of research specialists, from medical
anthropology to wildlife toxicology, to share findings about the effects of
chemicals on wildlife and human health, particularly the endocrine system.
Dr Colborn has been called the 'Rachel Carson of the 1990s'
and the Utne Reader(5) has predicted that she will have more impact on the
chemical industry than any other person in the 20th century. Dr. Colborn’s
new book, Our Stolen Future(6), co-authoured with Dr. John Peterson
Myers and Dianne Dumanoski tells the endocrine disruptor story.
What do endocrine disruptors do?
Wildlife—and humans—are daily being exposed to
synthetic chemical compounds that disrupt development of the reproductive,
immune, nervous, and endocrine systems. The pollutants of greatest concern
affect cellular and molecular processes that regulate developmental, endocrine
and immunological functions. Many of these contaminants mimic and/or interfere
with female and male hormones, thereby modifying development and reproduction.
For example, endocrine disruption may endanger populations by affecting their
immune systems, preventing recovery from infections. Or their ability to
obtain sufficient food or avoid predators could be affected. There is also
evidence that endocrine disruptors cause the loss of parenting instinct in
some bird species because of neuro-toxicological effects. Abnormal sexual
development or behaviour because of endocrine disruption can prevent
reproduction in sufficient numbers to sustain the population.
The main message for those working in the field of toxic
threats to biodiversity is that it is no longer sufficient to approach
population/species revitalization passively by providing appropriate habitat
and expecting threatened populations to recover(7). Habitat contamination is
not always visible, and it may not immediately kill the dependent organism,
but may cause population-threatening changes in the way an organism functions
in its environment.
The Wingspread scientists agreed that human beings are also
being affected by compounds of this nature. The reproductive effects reported
in wildlife should particularly concern humans where they are dependent upon
the same resources, for example, contaminated fish(8). Evidence of lowered
sperm counts(9) and significant increases in testicular cancer, breast cancer,
as well as of cases of undescended testes, is causing the concern.
What are the policy implications?
One of the great difficulties in identifying exactly
how these chemicals affect wildlife and humans is that the pattern of effects
varies between species and among compounds. General conclusions can be drawn,
however. The most important is that even one very low dose(10) of an endocrine
disruptor at a crucial stage in the development of an embryo is sufficient to
cause irreversible damage. Secondly, the gap between exposure and effect may
be a generation or two. In other words, the effects are 'transgenerational'—the
exposed individual may be completely unaffected whereas her offspring may have
reproductive difficulties. Thirdly, endocrine disruptor chemicals, like other
synthetic chemicals, can be cumulative or have synergistic effects.
Proper tracking of chemicals needed
The government and industry response needs to be
complex given the many implicated substances, the seriousness and range of
effects, and the time lag between cause and effect. The policy response needs
to cover many different factors—in civil society as well as in government.
It is very important that we gather more relevant data(11) to inform the
policy decisions on harmful synthetic chemicals released into the environment
and to allow each affected group to participate in safe and sound chemical
management.
As many persistent contaminants do not remain at the site
of release and can travel thousands of kilometres by air and sea, chemical
releases on one continent may affect not only animals and humans on that
continent but also on other continents and in other hemispheres. Contaminants
are carried as particulates or gases in the air, surface waters, groundwaters
and ocean currents as well as by animals that travel long distances. The
contaminant, therefore, can enter the food chain in places remote from the
site of release. Accordingly, the data collected and policy solutions must be
international.
Agenda 21 called for guidance for governments on chemical
inventories. Consequently, the Organization for Economic Cooperation and
Development (OECD) co-hosted five workshops(12) with the UN International
Programme for Chemical Safety (IPCS) on what are called internationally
Pollutant Release and Transfer Registers (PRTRs). PRTRs are a system of
tracking chemicals use, transfer and release, which record chemical specific
and standardized data on emissions of toxic substance to air, water and land.
Experiences with publicly-accessible PRTRs have shown them to be powerful
tools which lead to reductions in the use and release of toxics and the
adoption of less-polluting materials and technologies—cleaner production.
Establishing and linking these chemical registers in countries around the
world provides vital information on the sources of contamination by chemicals,
information critical in addressing substances which are increasingly
transported long distances through the air and water(13).
Precautionary phase-outs
The actual and potential impacts of endocrine
disruptors are so serious that action to eliminate and reduce the use and
production of some of these substances is justifiable now. Based on the
‘Precautionary Principle’(14), we must act now to halt the further
contamination of the environment, ecosystems, wildlife and humans. The
Wingspread I scientists came to the same conclusions: "Unless the
environmental load of synthetic hormone disruptors is abated and controlled,
large scale dysfunction at the population level is possible."
Growing consensus for elimination
Regional Seas Agreements have been in the forefront
of international commitment to reduction of toxics(15). At the second North
Sea Conference held in London in 1987, signatory countries agreed, amongst
other things, to reduce North Sea inputs of substances that are persistent,
toxic and liable to bioaccumulate(16). At the 3rd North Sea Conference, the
ministers agreed to phase out pesticides with these properties(17). At the 4th
North Sea Conference in 1995(18), the definition of toxicity was agreed to
include chronic effects such as carcinogenicity, mutagenicity and
teratogenicity and adverse effects on the function of the endocrine system.
| Pesticides considered to have
reproductive and endocrine disruptor effects 2,4,5-T, 2,4-D, alachlor, aldicarb, amitrole, benomyl, carbaryl, chlordane, cypermethrin, DBCP, DDT, dicofol, dieldrin, endosulfan, esfenvalerate, , fenvalerate, heptachlor, hexachlorobenzene, lindane, malathion, mancozeb, meneb, methomyl, methoxyxhlor, methyl parathion, metiram, metribuzin, mirex, nitrofen, oxychlordane, permethrin and other synthetic pyrethroids, toxaphene, transnonachlor, tributyltin oxide, trifluralin, vinclozolin, zineb, ziram(24). |
International action on POPs
Agenda 21(19) specifically called for States to
eliminate and reduce emissions or discharge of organohalogens and other
synthetic organic compounds that could accumulate to ‘dangerous levels’ in
the marine environment. In addition, States were urged to control and reduce
substances and wastes that are toxic, persistent or liable to bio-accumulate
This call to action has led to 109 countries to adopt a Global Programme of
Action for the Protection of the Marine Environment which included a
commitment to develop “...a global, legally binding instrument... for the
reduction and/or elimination of emission, discharges, whether intentional or
not, and, where appropriate, the elimination of the manufacture and use of,
and illegal traffic in, the persistent organic pollutants (POPs) identified in
UNEP Governing Council decision 18/32."(20,21)
Prevention at source
As can be concluded from this growing international
consensus, the need to phase out the production and use of certain toxic
chemicals is urgent and well founded. Yet, progress is slow on the
implementation of these international commitments, in part because governments
as well as the industrial and agricultural sectors are slow to embrace the
prevention/reduction philosophy and its implementation through clean(er)
production(22).
Several international fora and institutions support clean
production to eliminate pollution. Increasingly, this concept is framed to
include clean agricultural production which ultimately means no synthetic
inputs. As a long term sustainability goal this is laudable, however, in the
short and medium term, governments should implement national pesticide
reduction programmes which are based on consultation with, and the
participation of, the interested stakeholders—farmers, retailers, consumers
groups, environmental groups and agrochemical manufacturers. In order to
assess progress on pesticide reduction, governments need to set targets,
timetables and measures of use reduction in consultation with those
stakeholders.
Controls at the national level
Most governments have implemented laws requiring
stringent testing on new chemicals. However the fragmentation of government
agencies creates problems for an integrated review of, and action on,
chemicals on the market. Scientists and policymakers have in the past focused
their attention and efforts on the risks posed by a few hundred chemicals,
proceeding on a chemical-by-chemical basis, directed in large part by concerns
over acute toxicity, carcinogenicity, environmental persistence, and tendency
to bioaccumulate. But, a chemical-by-chemical approach is inadequate to
determine effectively or efficiently the safety of the roughly 100,000 already
in use and the 200 to 300 new products entering the market every year.
Moreover, this focus has overlooked the endocrine disruption problem.
All chemicals licensed for environmental release should be
tested throughout a minimum of two generations for a wide variety of effects
including reproductive, immunological, endocrinological and neurological
endpoints(23). Chemicals should be assumed guilty of endocrine disruption
until proven innocent.
Barbara Rutherford is Policy Coordinator: Water Pollution and Toxics, World Wide Fund for Nature International, Avenue Mont-Blanc CH-1196 Gland, Switzerland, Tel. +41 22 364 9111, Fax +41 22 364 5358.