Endocrine
Disruptors
What
are Endocrine Disruptors?
Hormones are chemical messengers that are produced by
endocrine glands in the body such as the pituitary, the
thyroid, the adrenal glands, the ovaries, and the testes.
They circulate throughout the body and control metabolism,
growth, development, and some aspects of human behavior.
Evidence is increasing that some synthetic chemicals in
the environment can interfere with hormone function. They
can do this by blocking the effects of a natural hormone,
by mimicking a natural hormone, or by directly interfering
with the endocrine glands. Chemicals that have this capability
are called endocrine disruptors. These substances have
been shown to be able to alter the function of estrogen,
androgen, thyroid hormone, and even the hormones of the
pituitary gland.
What
Chemicals are Responsible?
Certain insecticides, herbicides, fumigants, and fungicides
as well as industrial chemicals such as detergents, resins,
and plasticizers are among the kinds of chemicals that
are proven or suspected endocrine disruptors. Some of
these substances have been banned in the U.S. at least
in part because of their ability to interfere with the
endocrine system. These banned substances include the
insecticide DDT, DES (diethylstilbestrol), a synthetic
estrogen prescribed in the 1950s and 1960s to prevent
miscarriage, and PCBs (polychlorinated biphenyls), electrical
insulating chemicals that are highly persistent in the
environment and accumulate in the fatty tissue of animals.
It is unknown how many endocrine disruptors are currently
in use because most industrial chemicals have not been
tested for their ability to interfere with the endocrine
system.
How
are Humans Exposed to Endocrine Disruptors?
Humans may be exposed to endocrine disruptors through
inhalation, through the skin, or through food and water.
People can come into direct contact with endocrine disruptors
in the workplace or at home. Air can be a source of exposure.
Humans may ingest endocrine disruptors through food and
through breast milk. Endocrine disruptors can persist
in sediments for years and can contaminate areas far removed
from the source of contamination. Because so little is
known about the endocrine disruption potential of most
chemicals, it is difficult to determine exposure patterns
in humans.
Body
Burdens
All humans are exposed to endocrine disrupting chemicals.
Each of us has a "body burden" of a mixture
of numerous industrial chemicals and heavy metals in our
tissues, blood, fat, sperm, breast milk, and amniotic
fluid. The best known of these contaminants is lead. Others
include pesticide residues (DDT and DDE), dioxins, and
PCBs. With the exception of lead, we do not know the significance
of the chemical exposures indicated by these body burdens.
What
are the Health Effects of Endocrine Disruptors?
While human exposure to these substances is ongoing, fundamental
questions about their effects have yet to be answered.
Endocrine disruptors have been linked to significant declines
in some wildlife populations, such as fish and birds of
the Great Lakes region and alligators of Lake Apopka,
Florida. They have been linked to a wide range of abnormalities
in wildlife and laboratory animals, such as thinned eggshells,
abnormalities of the reproductive tract, and suppression
of the immune system.
Far
less is known about the effects of endocrine disruptors
in humans. Understanding the possible effects on human
health of toxic environmental exposures is difficult for
several reasons: 1) Humans are potentially exposed to
thousands of chemicals in the environment, most of which
have not been screened for their ability to disrupt the
endocrine system; 2) Humans are exposed to mixtures of
substances, and the possible cumulative effects of these
mixtures have yet to be determined; and 3) Human health
outcomes may be subtle, unreported, or delayed.
Despite
these uncertainties, endocrine disruptors have been suspected
of contributing to a range of adverse health effects in
humans, including reproductive and developmental disorders,
learning problems, and immune system dysfunction. Several
recent trends in human health may be related to endocrine
disruptors in the environment: widespread occurrence of
neurobehavioral dysfunction at birth and in childhood;
an increasing incidence of testicular cancer in young
men; an increasing incidence of congenital malformations
of the male reproductive tract; the increasing incidence
of breast cancer; and declining sperm counts.
Exposure
to endocrine disruptors during pregnancy may have significant
health risks because of the particular vulnerability of
developing organ systems. Disturbances of the early course
of human development could lead to lifelong alteration
of behavior or endocrine function.
This
summary was prepared by the Center for Children's Health
and the Environment of the Mount Sinai School of Medicine.
CCHE's mission is to promote the health of children by
conducting environmental health and policy research. CCHE
was established in 1998 with the support of The Pew Charitable
Trusts. CCHE's director is Philip J. Landrigan M.D., M.Sc.,
a pediatrician who chairs the Department of Community
and Preventive Medicine at Mount Sinai.
Simple
precautions:
