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What
is endocrine disruption? What are endocrine disrupters? |
The
International Programme for Chemical Safety has
established the following definition for endocrine
disrupters:
Endocrine disrupters have been defined
as exogenous substances that alter function(s)
of the endocrine system and consequently cause
adverse health effects in an intact organism,
or its progeny, or (sub)populations. |
Endocrine disrupters interfere with the functioning
of the endocrine system, in at least three possible
ways:
- by mimicking the action of a naturally-produced
hormone, such as oestrogen or testosterone, and
thereby setting off similar chemical reactions in
the body;
- by blocking the receptors in cells receiving the
hormones (hormone receptors), thereby preventing
the action of normal hormones; or
- by affecting the synthesis, transport, metabolism
and excretion of hormones, thus altering the concentrations
of natural hormones.
Classification
There are two classes of substances which can cause
endocrine disruption:
- Natural hormones, which include
oestrogen (responsible for female sexual
development), progesterone and testosterone
(=androgens: responsible for male sexual development)
found naturally in the bodies of humans and animals,
and phytoestrogens, substances contained
in some plants, such as alfalfa sprouts and soya
beans, which display oestrogen-like activity when
ingested by the body. Natural hormones are believed
to be easily broken down in the human body; thus
they do not accumulate in body tissues, which is
the case with certain man-made substances.
Chemical structure
of the testosterone hormone. Image
source
- Man-made substances which include:
1. Synthetically produced hormones,
including those hormones which are identical to
natural hormones, such as oral contraceptives,
hormone-replacement treatment and some animal
feed additives, which have been designed intentionally
to interfere with and modulate the endocrine system;
and
2. Man-made chemicals (thousands
of new and existing man-made chemicals exist)
designed for uses in industry, such as in industrial
cleaning agents, in agriculture, in certain pesticides,
and in consumer goods such as in plastic additives.
This group also includes chemicals produced as
a by-product of industrial processes such as dioxins,
which are suspected of interfering with the endocrine
systems of humans and wildlife. Some of the potential
environmental endocrine-disrupting chemicals (EDCs)
are persistent and ubiquitous in the environment
(persistent
organic pollutants – POPs ).
The following groups of chemicals have
already been identified as affecting the endocrine
system:
- Polychlorinated biphenyls
(PCBs), dioxin
and benzo(a)pyrene
(industrial processes). Interfere with components
in the steroid, thyroid and retinoid signalling
pathways. For more information, see http://www.atsdr.cdc.gov/tfacts17.html
- Products associated
with plastics:
{i} Phthalates (plasticisers, e.g. in PVC).
For more information, see http://website.lineone.net/~mwarhurst/phthalates.html
or http://www.phthalates.com/index.asp?page=5
{ii} Bisphenol A (lacquers).
For more information see
http://website.lineone.net/~mwarhurst/bisphenol.html,
http://ec.europa.eu/food/fs/sc/sct/out156_en.pdf,
http://ec.europa.eu/food/fs/sc/sct/out159_en.pdf,
http://www.bisphenol-a.org/,
and
http://ec.europa.eu/food/fs/sc/scf/out128_en.pdf.
- Pesticides (insecticides
such as o,p´-DDT, endosulfan, dieldrin, methoxychlor,
kepone, dicofol and toxaphene; herbicides
such as alachlor, atrazine and nitrofen; fungicides
such as benomyl, mancozeb and tributyl tin);
nematocides such
as aldicarb and dibromochloropropane). See more
information on http://docs.pesticideinfo.org/documentation4/ref_toxicity5.html
- Ordinary household products such as alkylphenols
(e.g. nonylphenol). For more information see
http://www.foe.co.uk/resource/reports/ethoxylates_alkylphenols.pdf
- Heavy metals
(lead, mercury, cadmium). For more information,
see http://www.ourstolenfuture.com/Basics/chemlist.htm
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