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Persistent Organic Pollutants (POPs)
General Facts about Persistent Organic Pollutants (POPs)
- Persistent organic pollutants (POPs) are organic compounds that resist environmental breakdown via biological, chemical, and photolythic processes, some taking as long as a century to degrade.
- POPs exposed to the environment are proven to travel long distances from their origin via wind and ocean currents. Precipitation has been found to carry PCBs (polychlorinated biphenyls)
- POPs therefore can be found globally, even in areas such as the Arctic and Antarctica, far from their source. Human exposures in certain Arctic areas are among the highest worldwide.
- POPs bio-concentrate as they move up through the marine food chain and accumulate in the fatty tissues of living organisms at higher trophic levels.
- Marine mammals around the world carry high burdens of POPs.
- Although many countries have banned these chemicals, they remain stockpiled, are produced or used illegally, or, because of lengthy half-lives, they continue to exist in soil, or other environmental media.
- The United Nations is currently considering the elimination or reduction of twelve of some of the most damaging POPs through the formulation of an international treaty. Nine of the POPs chemicals under consideration are pesticides that have been extensively used in both developed and developing countries.
General Health Effects of Persistent Organic Pollutants (POPs)
- POPs can disrupt the endocrine, reproductive, and immune systems. The developing brain and nervous system may be most vulnerable.
- POPs are capable of causing behavioral problems, cancer, diabetes and thyroid problems.
- According to a landmark longitudinal study, babies whose mothers ate large amounts of highly contaminated fish (PCBs were measured) from Lake Michigan had lower birth weights, smaller head circumferences and shorter attention spans than babies whose mothers did not eat fish. Followed over 11 years, the exposed children have continued to do poorly in a range of skills and development tests, including deficits in general intellectual functioning, short- and long-term memory, and attention span.
- The health of marine mammals has deteriorated significantly over the past two decades. Many of the newly emerging and resurgent diseases are associated with immune system dysfunction and suggest a broad environmental distress syndrome.
- Marine mammals present a metabolic imbalance, so they are considered one of the most vulnerable organisms with respect to long-term toxicity of man-made chemicals such as organochlorines. Cetaceans (whales and dolphins) are known to have a poor ability to detoxify organic pollutants because they lack isozymes that are required to detoxify DDT and PCBs.
"The Dirty Dozen" Persistent Organic Pollutants (POPs)
These 12 POPs are often referred to as the "dirty dozen":
Aldrin – an organochlorine insecticide;
- A pesticide used to control soil insects. It has been widely used to protect crops such as corn and potatoes, to protect wooden structures from termites.
- It is oxidized in the insect to form dieldrin, a neurotoxin.
- It is a carcinogen as well as a mutagen.
- It binds strongly to soil particles, is resistant to leaching into ground water. It is released from soil by volatilization.
- Due to its persistent nature, aldrin is known to bio-concentrate.
- Aldrin is toxic to humans causing headache, dizziness, nausea, general malaise, and vomiting, followed by muscle twitchings, myoclonic jerks, and convulsions.
- Occupational exposure to aldrin, in conjunction with dieldrin and endrin, has been associated with a significant increase in liver and biliary cancer. -Aldrin may affect immune responses.
- Many countries, including the US have ended its usage and manufacture
- It is a carcinogen as well as a mutagen.
Chlordane – a manufactured pesticide;
- Chlordane is a broad spectrum contact insecticide that has been used on agricultural crops as well as being used extensively in the control of termites
- Banned in US in 1988 by the EPA;
- Chlordane sticks strongly to soil particles at the surface and is not likely to enter groundwater. As a result it can stay in the soil for over 20 years and breaks down very slowly.
- Bio-concentrates in fish, mammals, and birds;
- In both humans and animals, it can damage nervous and digestive systems, and liver - Has caused convolutions and death;
- Recent human studies have linked chlordane exposure with prostate and breast cancers.
DDT – a synthetic pesticide
- DDT is a toxicant;
- It has a half life of 2-15 years,
and is immobile in most soils
- Breakdown products
in the soil environment are DDE and DDD, which are also
highly persistent and have similar chemical and physical
- Banned in the US for most uses in
- Subsequently banned for agricultural
use worldwide, but is still used to a limited extent
in mosquito control in certain parts of the world
use of DDT was found to be a major factor in the bald
eagle and the peregrine falcon population decline, as
it caused the birds’ egg shells to thin.
and its metabolic products DDE and DDD magnify through
the food chain
- DDT bio-concentrates significantly
in fish and other aquatic species, leading to long-term
exposure to high concentrations.
- At the chronic
level, individuals who consumed contaminated fish increased
- The EPA, in 1987 , classified
DDT as a probable human carcinogen.
- In 2007 a
Canadian study found a positive association between DDE
and non-Hodgkins Lymphoma.
- Tests conducted by
the CDC in 2002 showed that more than half of subjects
tested had detectable levels of DDT or metabolites in
- The USDA tested cows milk samples
in 2005 and found that 85% had detectable levels of DDE.
Dieldrin – an insecticide;
- Closely related
to aldrin which itself breaks down to form dieldrin
accumulates as it is passed along the food chain.
exposure is toxic to many animals (humans included) far
greater than to the original insect targets;
banned in most of the world;
- Linked to Parkinson’s
disease, breast cancer and immune, reproductive, and
nervous system damage.
Endrin – an insecticide/rodenticide;
in many countries;
- It is likely to adsorb onto
the sediments in surface water.
- An insecticide
used on cotton, maize, and rice; a rodenticide used to
control mice and voles
- It can bio-concentrate
in the fatty tissues, of organisms living in water. It
is very toxic to aquatic organisms, namely fish, aquatic
invertebrates, and phytoplankton.;
in soil estimated at over a decade;
- Endrin poisoning
in humans primarily affects the nervous system. Food
contaminated with endrin has caused several clusters
of poisonings worldwide, especially affecting children.
Heptachlor – an insecticide;
- Similar to
the insecticide chlordane
- The U.S. has banned
the sale of heptachlor products in the United States
and virtually eliminated its use for any purpose
a very stable structure, thus it can remain in environment
- Possible human carcinogen.
(HCB) – a fungicide;
- A fungicide formerly
used as a seed treatment, especially on wheat.
animal carcinogen (liver, kidney, thyroid);
- After its introduction as
a fungicide in 1945, for crop seeds, this toxic chemical
was found in all food types.
- Banned in the U.S
- In humans it can cause liver disease,
skin lesions, ulceration, hair loss, thyroid damage;
and animal studies have demonstrated that HCB crosses
the placenta to accumulate in fetal tissues and is transferred
in breast milk.
- Extremely toxic to aquatic creatures.
Risk of bioaccumulation in an aquatic species is high
Mirex – an insecticide, flame retardant;
as a persistent, accumulative, and toxic pollutant by
EPA in the U.S.
- It was used to control fire ants
and as a flame retardant in plastic, rubber, paint, paper
- Mirex is transported across the
placenta and can be passed from mother to child through
- Most effected in animals is the liver;
to cause cancer in mice and rats and is a carcinogenic
risk to humans;
- Toxic for a range of aquatic
organisms, with crustacea being particularly sensitive.
induces pervasive long-term physiological and biological
disorders in vertebrates.
- There is evidence
of accumulation of mirex in aquatic and terrestrial food
chains to harmful levels
- Mirex is one of the most
stable of the organochlorine insecticides and is it is
widespread in the environment.
- All uses of mirex
as a pesticide were banned in the U.S. in 1978.
is still used in the USA mainly as a flame-retardant
in plastics, rubber, paint, paper and electronics.
on organisms combined with its persistence suggest that
mirex presents a long-term hazard for the environment
PCBs (polychlorinated biphenyls)
- Used as coolants/insulating
fluids, also used in flexible PVC coatings of electrical
wiring and electronic components, pesticide extenders,
cutting oils, flame retardants, hydraulic fluids, sealants
(used in caulking, etc), adhesives, wood floor finishes,
paints, and in carbonless copy paper.
are very stable compounds and do not degrade readily.
being banned in the 1970s due to their high toxicity,
PCBs still persist in the environment
to the ban estimates have put the total global production
of PCBs on the order of 1.5 million tons
have been detected globally in the atmosphere, from the
most urbanized areas that are the centers for PCB pollution,
to regions north of the Arctic Circle, carried by wind
- Bio-concentrates in animals;
can be transmitted to children via breast milk as well
as through the placenta.
- In humans, PCBs can
cause liver disease, ocular lesions, lessened immune
- Babies born to women exposed
to PCBs have been shown to weigh less, have problems
with motor skills, a decrease in short-term memory, and
compromised immune systems.
- PCBs alter estrogen levels
in the body and contribute to reproduction problems.
Disrupting Chemicals (EDC's) such as PCBs pose a serious
threat to reproduction in top-level predators.
magnification of PCBs has led to polar bears and whales
that have both male and female sex organs and males that
- Effects on animals are liver,
stomach, thyroid damage, plus immune system changes,
changes in behavior, impaired reproduction
studies indicate that PCBs are associated with cancer
in humans, such as cancer of the liver and biliary tract.
Recent research by the National Toxicology Program has
confirmed that PCB126 is a carcinogen.
are known to induce Vitamin A deficiency in mammals,
an affect that may be associated with impairment of the
immune system, reproduction and growth.
dibenzodioxins) – commonly referred to as DIOXINS
are teratogens (cause birth defects), mutagens, potential
- Known to accumulate in humans
and wildlife due to dioxins’ ability to dissolve
in fats and oils and their tendency to be water insoluble.
This means that even small amounts in contaminated water
can bio-concentrate up the food chain to dangerous levels.
- In humans, they can cause effects in reproductive/sexual
development, plus immune system damage, thyroid disorders,
nervous system disorders, endometriosis and diabetes.
animals and fish, studies have shown dioxin exposure
to cause cancer birth defects, liver damage, endocrine
damage, and immune system suppression.
have shown that exposure to dioxin increases the ratio
of female births to male births among a population.
of dioxins are found in all humans today, with higher
levels found in persons living in more industrialized
- The estimated elimination half-life
for dioxins in humans ranges from 7.8 to 132 years.
enters the general population almost exclusively from
ingestion of food, specifically through the consumption
of fish, meat, and dairy products since dioxins are fat-soluble
and readily climb the food chain
- Because Dioxins
are lipophilic, breast fed children usually have substantially
higher dioxin body burdens than non-breast fed children
until they are about 8 to 10 years old.
to the EPA, 80% of Dioxin emissions are caused by coal
burning plants, municipal waste incinerators, metal smelting,
diesel trucks, land application of sewage sludge, burning
treated wood and trash burn barrels. Dioxins are also
generated in bleaching fibers for paper and textiles.
- Highly toxic;
and chemical structure similar to dioxins;
Toxaphene – an
- Highly toxic
- Banned in US
in 1990, outlawed in 1991 by the Stockholm Convention
can cause damage to lungs, nervous system, kidneys and
can be fatal
Additional Persistent Organic Pollutants (POPs)
PBDEs – (Polybrominated
diphenyl ethers) flame retardants
- PBDEs are
used in plastic, foam and textiles in clothing, computers,
televisions, furniture and cars.
- PBDEs have
been found at high levels in indoor dust
has linked some chemicals in the flame retardants to
effects on thyroid function on brain function, reduced
male fertility and damaged ovarian development and the
development of the embryonic nervous system, impacting
motor skills and behavior.
- These chemicals were
banned in Europe in 2004/2005. In August 2003, California
became the first state to ban two forms of the fire retardants
chemicals known to accumulate in the blood of mothers
and nursing babies. In April 2007 Washington banned the
use of PBDEs and in May 2007, the state of Maine passed
a bill phasing out the use of DecaBDE.
of concentration in humans and marine mammals continue
to increase, particularly in the United States.
have found that PBDEs accumulate in human blood, fat
tissue and breast milk. It has been found that a woman
can pass these chemicals to her unborn child through
- In the United States levels in
human breast milk are 40 times higher than in Europe
and are steadily rising.
- Marine mammals like bottlenose
dolphins, harbor porpoises, pilot and beluga whales have
been found to be contaminated with PBDEs. Birds including
cormorants and glaucous gulls, and popular food fish
including salmon and tuna have also been found to carry
high concentrations of PBDEs
PFCs – perflorinated
- PFCs are used as industrial and commercial
surfactants - wetting agents that lower the surface tension
- In contrast to the majority of organic
pollutants that are deposited in fatty tissue, perflorinated
contaminants circulate in the blood and accumulate primarily
in the liver.
- PFCs are synthetic molecules
that are thought to bioaccumulate and are believed to
be extremely resistant to physical degradation, biodegradation,
- Science has begun to
demonstrate clear links between chemicals such as phthalates,
bisphenol A, and perflorinated compounds found in consumer
products including baby bottles, toys, and cosmetics
to reproductive disorders.