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Timeline of Endocrine Disruption
and Man-Made Chemicals
The following timeline is based on a PBS feature aired in February
of 1998 and featuring interviews with Theo Colborn, author of Our
Stolen Future, Lois J. Guillette, PhD, and Fredrick Vom Saal.
1923 First estrogen bioassay is developed. The test
detects estrogenic activity in biological extracts and determines relative
potencies of compounds and mixed natural materials.
1929 Commercial production of PCBs begins in the United
States in response to the electrical industry's need for a safer cooling
and insulating fluid for industrial transformers and capacitors.
1938 British scientist and physician Edward Charles
Dodds announces the synthesis of a chemical that acted in the body like
a natural estrogen. Called DES, it is hailed by leading researchers
and gynecologists as a wonder drug with a host of potential uses. (Dodds
was later knighted for his scientific achievement.) Soon after Dodds
invents DES, researchers in the United States begin giving the synthetic
hormone to women with problem pregnancies. The massive experiment would
eventually involve an estimated 4.8 million pregnant women worldwide.
1948 Paul Muller is awarded a Nobel Prize in medicine
for discovering the insect-killing properties of DDT.
1950 DDT is shown to disrupt sexual development in
roosters--possibly by acting as a hormone. Scientists V.F. Lindeman
and Howard Burlington find that young roosters treated with DDT fail
to develop normal male sex characteristics, such as combs and wattles.
The pesticide also stunted the growth of the animals' testes. These
scientists noted a similarity between DDT and DES, a synthetic estrogen
given to women for problem pregnancies. DDT, they observe, "may exert
an estrogen-like action" on the animal in question.
1952 By this date, 4 separate scientific studies show
women treated with DES to prevent miscarriage did no better than those
treated with alternatives such as bed rest or sedatives. Further analysis
will show that DES actually increases the number of miscarriages, premature
births and deaths among infants.
1962 Silent Spring is published. Rachel Carson's
book describes health problems observed in wildlife such as eggshell
thinning, deformities and population declines. Carson links these adverse
effects to exposure to pesticides and other synthetic chemicals.
1963 Study shows that newborn mice receiving estrogen
injections developed tissue pathologies such as cysts, cancers and lesions.
Results indicate that exposure to naturally occurring hormones early
in life can produce harmful health effects and point to possible early-life
causes of cancer in adult human populations.
1968 DDT is shown to be estrogenic in mammals and birds.
1971 DES is linked to vaginal cancer in daughters whose
mothers had taken the drug during the first three months of pregnancy.
By this date, millions of pregnant women had received prescriptions
from physicians for DES. The US Food and Drug Administration directs
doctors not to prescribe DES to pregnant women and bans the drug for
animal use.
1972 DDT use is restricted in agriculture by the US
Environmental Protection Agency.
1973 International Joint Commission (IJC) for the
US and Canada singles out first "Areas of Concern" in the Great Lakes
region, noting extensive pollution and threats to wildlife.
1976 DES is shown to cause developmental abnormalities
in male mice and reproductive problems in humans.
1977 Use and manufacture of PCBs restricted by the
U.S. Environmental Protection Agency. PCBs continue to be manufactured
and sold overseas .
1978 Great Lakes Water Quality Agreement between US
and Canada calls for virtual elimination of persistent toxic substances
from Great Lakes basin.
1979 National Institute of Environmental Health Sciences
holds conference entitled: Estrogens in the Environment I. Presented
papers identify and evaluate both advertent and inadvertent hormone
mimics. Manufacture of PCBs banned in the US, but not their use or storage.
1982 DES is shown to cause developmental abnormalities
and vaginal cancer in female mice.
1983 Responding to public concern over dioxin contamination
at Times Beach, Love Canal, Jacksonville and other sites, the US Congress
directs the EPA to conduct a National Dioxin Study to determine the
extent of contamination nationwide.
1985 National Institute of Environmental Health Sciences
holds a conference called Estrogens in the Environment II: Influences
on Development. Presentations address the effects of environmental estrogens
on puberty in young children. Also noted is the ubiquitous nature of
the contaminants, their potency and their potential impact on public
and environmental health. EPA's Dioxin Risk Assessment classifies dioxin
as a known animal and probable human carcinogen, setting the lowest
"safe exposure level" on record.
1985 Eight Great Lakes states develop remedial action
plans to address environmental damage seen in IJC-targeted "Areas of
Concern."
1986 Documents are leaked to Greenpeace showing EPA
agreed to demands from the paper industry to keep results of National
Dioxin Survey secret. Under threat of lawsuit, EPA releases National
Dioxin Survey. The study finds dioxin is present in discharge from paper
mills and in finished paper products (due to chlorine bleaching of white
paper).
1986 Paper industry pressures EPA to reconsider its
1985 Dioxin Risk Assessment in hopes of obtaining a less damaging judgment
on dioxin's health effects.
1988 EPA begins its first reassessment of dioxin.
1990 The EPA and the Chlorine Institute (an industry
group) co-sponsor the Banbury Conference on Dioxin, which takes place
on Long Island, New York. Conference attendees reach a consensus on
dioxin's probable mechanism of action. Theo Colborn co-authors "Great
Lakes, Great Legacy?," detailing developmental, reproductive, metabolic
and behavioral damage to wildlife from persistent chemical pollutants.
1990 Fifth Biennial report of IJC puts threat in plain
language, saying that the principal danger of persistent organochlorine
chemicals is to the fetus.
1990 Environmental groups around the Great Lakes form
the Zero Discharge Alliance to oppose production of bioaccumulative
toxic substances.
1991 Theo Colborn helps organize a conference called
"Chemically Induced Alterations in Sexual Development: The Wildlife-Human
Connection" and held at Wingspread in Racine, Wisconsin. For the first
time, scientists from many disciplines are brought together to discuss
concerns about endocrine-disrupting chemicals in the environment. Participants
present evidence that compounds may have deleterious effects on sexual
development in a variety of wildlife species. Possible impacts include
reproductive system abnormalities, reduced fertility, behavioral abnormalities,
and population declines--particularly in top predators. Researchers
Ana Soto and Carlos Sonnenschein report that some plastic compounds
widely used in a variety of consumer products are estrogenic in laboratory
research.
1991 The Chlorine Institute (an industry group) prematurely
issues a press release stating that below a certain threshold of exposure,
dioxin has no adverse effects. Group makes false claim that this was
the consensus of the Banbury Conference.
1991 EPA administrator Bill Reilly states publicly
that dioxin seems less dangerous than previously thought. He initiates
a second EPA reassessment of dioxin.
1991 Greenpeace tours 40 Great Lakes cities by boat
in preparation for upcoming IJC meeting in Traverse City, Michigan.
The publicity campaign focuses on the goal of zero dioxin discharge
by the paper industry. Greenpeace distributes a report entitled: "The
Product is the Poison: The Case for a Chlorine Phase-Out."
1992 Sixth Biennial Report of the IJC calls for a phase-out
of chlorine as an industrial feedstock. Drinking water and pharmaceutical
uses are exempted. Environmental groups and industry are surprised by
this wide-reaching recommendation.
1992 Physician Niels Skakkebaek publishes a paper
demonstrating that human sperm counts may have declined 50 percent over
the last 50 years.
1993 Referring to the perceived decrease in human
sperm counts, scientist Lou Guillette tells the US Congress, "Every
man sitting in this room today is half the man his grandfather was,
and the question is, are our children going to be half the men we are?"
A link between environmental estrogens and male reproductive problems
is hypothesized in scientific papers.
1993 Chemical Manufacturers' Association forms the
Chlorine Chemistry Council (CCC) to promote the industry's agenda in
the debate over chlorine chemistry. CCC launches a public relations
campaign, including television advertisements asserting the need for
chlorine.
1994 EPA releases a Public Review Draft of its Dioxin
Reassessment. It covers dioxin, dioxin-like PCBs and furans. The report
concludes that these chemicals cause harm at levels similar to those
seen in the general public. In addition to cancer, potential damage
is seen to the immune, nervous and reproductive systems.
1995 The National Academy of Sciences and National
Research Council sponsor a panel study called "Hormone Related Toxicants
in the Environment." The EPA's Science Advisory Board reviews draft
of Dioxin Reassessment.
1996 The topic of endocrine disrupters is popularized
with the publication of Our Stolen Future, which is co-authored
by Theo Colborn and includes an introduction by U.S Vice President Al
Gore.
1996 President Clinton signs the Food Quality Protection
Act and amendments to the Safe Drinking Water Act, establishing the
EPA's Endocrine Disruptor Screening and Testing Advisory Committee (EDSTAC).
EDSTAC is a unique advisory committee of 40 members from industry, academia,
government and environmental groups. It is charged by Congress to develop
a chemical screening program for endocrine disruptors by 1998, and to
implement the program by August, 1999.
1996 Scientist Lou Guillette publishes his finding
that male alligators in Florida's Lake Apopka have strikingly low levels
of testosterone and abnormally small phallus size. Pesticide residues
in this contaminated lake appear to have "feminized" the alligators
there.
1996 Psychologists Sandra and Joe Jacobson report
that children exposed to high levels of PCBs before birth have as much
as a 6.2 point IQ deficit later in life.
1996 Dr. Harry Fisch publishes a study refuting any
decline in US sperm counts. He found, instead, striking geographical
variation in sperm counts across the U.S. While sperm counts remained
constant in a given region between 1970 and 1994, New York had higher
counts than Minnesota, which had higher counts than California. Fisch
thinks that the geographical variation may have confused other research
that, in 1992, showed a worldwide decline in human sperm counts.
1997 Work by researcher Dr. Fredrick vom Saal shows
that bisphenol-A, a component of polycarbonate plastic, can alter the
reproductive development of lab mice at extremely low doses. Bisphenol-A
mimics the natural sex hormone estrogen. Male mice exposed to this plastic
during fetal development have premanently enlarged prostates and lower
sperm counts. The effects occur at doses near those that humans are
exposed to each day from sources like food packaging and dental sealants.
1997 A study by the Centers for Disease Control and
Prevention shows that hypospadias, a hormone-dependent genital defect,
is on the rise in baby boys.
1997 The National Institute of Environmental Health
Sciences (HHS) holds its fourth major conference on estrogens in the
environment in Arlington VA. Numerous scientific papers and reports
are presented on toxicology, risk assessment and research for this emerging
health concern.
1997 Tulane University scientists retract an environmental
estrogen study published in a June 1996 issue of Science. The report
had claimed that combinations of pesticides were as much as 1,600 times
more potent as environmental estrogens than the individual pesticides.
The research results couldn't be replicated and the study was retracted.
1998 The National Academy of Sciences Institute of
Medicine is expected to issue its report on hormone-related toxicants
in the environment. The NAS panel will critically review the literature,
identify known and suspected impacts on fish, wildlife and humans, and
recommend research, monitoring and testing priorities, among other activities.
By August, the EPA committee EDSTAC is mandated to develop recommendations
on how to screen and test chemicals for their potential to disrupt hormone
function in humans and wildlife. EDSTAC's final plenary session is set
for June 17-18 in Washington, D.C.
1998 A research paper published in the Journal
of the American Medical Association reports that the proportion
of males to females born has been declining in the US and Canada since
the 1970s and in Denmark and the Netherlands between 1950 and 1994.
The study's authors suggest that endocrine disruptors may play a role,
pointing to increased numbers of male reproductive disorders. When the
study is reported in the popular press, some scientists downplay the
significance of the reported trend.
1998 Vice President Al Gore urges the chemical industry
to voluntarily release vital health information about thousands of commonly
used chemicals. He says such a move would "empower citizens with new
knowledge" to safeguard their neighborhoods against potential chemical
hazards.
1998 The United Nations Environment Programme meets
in Montreal to expand throughout the world an agreement to ban, phase
out or limit the production of Persistent Organic Pollutants (POPs).
POPs are chemical substances that persist in the environment, bioaccumulate
through the food web, and pose a risk of causing adverse effects on
human health and the environment. Persistent Organic Pollutants include:
aldrin, dieldrin, endrin, chlordane, DDT, heptachlor, hexachlorobenzene,
mirex, toxaphene, PCBs, dioxins, and furans.
1998 On Earth Day, the Chemical Manufacturers' Association
announces it will urge its members to voluntarily increase their health
effects testing program of industrial chemicals to 100 chemicals a year
by 2003.
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