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Science Forum Index » Environment Forum » Evidence of chemical effects on children mounts
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| Ilena |
 Posted: Sat Dec 20, 2003 10:11 am |
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~~~ thanks to Ashley for forwarding this important article ~~~
http://www.shns.com/shns/g_index2.cfm?action=detail&pk=CHILDBRAIN-12-16-03
Evidence of chemical effects on children mounts
By JOAN LOWY
Scripps Howard News Service
16-DEC-03
At Massachusetts General Hospital in Boston, Dr. Martha Herbert is
seeing younger and younger children who have been prescribed powerful
drugs because their behavior is "so extreme."
One 4-year-old was treated with Risperdol, an antipsychotic drug
usually prescribed to adult schizophrenics, because she tried to kill
a sibling. "I've had several cases like that," said Herbert, a
pediatric neurologist. "It's scary because this kind of thing hardly
ever used to happen."
Across the nation, evidence of a growing number of children diagnosed
with attention, learning, behavioral and emotional disorders have
perplexed doctors and researchers and worried teachers and parents.
The disturbing conclusion some experts are reaching is that a
significant share of these conditions may be caused by environmental
toxins that interfere with brain development in children beginning in
the womb and which may be lowering the intelligence of the population
at large.
There is no shortage of toxic suspects including lead, PCBs, mercury,
pesticides, dioxins, flame-retardants and alcohol. Most children are
exposed to some level of all these chemicals, raising the possibility
of combined effects _ a question that scientists are only now
beginning to research.
"You can almost think of the children who have been diagnosed with
these clinical syndromes as the tip of the iceberg," said Deborah
Rice, a toxicologist with the Maine Department of Environmental
Protection.
"These are the kids that stand out, the ones that can actually go into
a doctor's office and the doctor can say, 'Yes, this child has
autism,' " Rice said. "But for every one of those children there may
be many more children that don't reach the clinical criteria, but
nonetheless may have been affected by the chemicals and other
environmental milieu of a child's life."
Autism researcher George Lambert describes children as society's
"canaries in the coal mine" because they are so much more sensitive
than adults to poisons in the environment. They eat more food, breathe
more air and drink more fluid per pound of body weight than adults _
and their brains and nervous systems are still developing. The most
sensitive of all is the developing fetus.
In California, state health authorities have documented a 273 percent
increase between 1987 and 1998 in diagnosed cases of autism, a
neurodevelopmental disorder that usually appears before age 3 and can
affect a child's ability to communicate, form relationships and
respond to the world around them.
Reported autism cases in California doubled again over the last four
years and the rate of increase appears to be accelerating, according
to a follow-up study released earlier this year. In November, the U.S.
Department of Health and Human Services held a two-day "autism summit"
in Washington in response to demands from parents of autistic children
for greater federal action to counter what they call a national
"epidemic" of autism.
In North Port, Fla., kindergarten teacher Susan Owens said she has
seen a dramatic increase in attention and learning disorders in
children of all levels of intelligence and family income over the last
30 years.
Retarded students she taught in the late 1960s were better able to
retain basic knowledge and skills such as the days of the week or
simple addition and subtraction than many of today's kindergarteners
of average intelligence, said Owens, 60.
"I can go over the days of the week with my children now the entire
year, but if I say to them, 'Today is Friday. What will tomorrow be?'
50 percent of them will still not be able to tell me that tomorrow is
Saturday," Owens said.
Epidemiologists caution that personal observations or even documented
trends in diagnosis are not proof that any of these disorders is
increasing in children. Only a national study that investigates and
tracks tens of thousands of children _ something that has never been
done in the United States _ would be able to determine the true
prevalence of these problems and whether they are actually increasing.
"One can say there has been an increase in conduct disorders _ in
violent and aggressive behaviors _ over the last 50 years in children,
but the problem with saying the same thing about ADHD (attention
deficit/hyperactivity disorder) or autism is that we simply don't have
good enough data to draw conclusions," said Jane Costello, a
psychiatric epidemiologist at Duke University Medical Center.
What is clear is that scientific understanding of the potential
effects that toxins can have on the human brain has expanded markedly.
Scientists now know that the timing of the exposure is just as
critical as the amount _ or dose _ of the toxin. Very small amounts of
chemicals at critical windows in fetal development or early childhood
can have far more devastating effects than greater exposure later in
life.
Scientists also know more about the relationship between genes and
environment in the creation of disease. Even as researchers are
linking individual genes to specific diseases, they are also
discovering that particular substances in the environment can "turn
off" or "turn on" these genes. The description often used by
scientists is that "genetics loads the gun, but environment pulls the
trigger."
Studies of identical twins show that 68 percent of the time when one
twin has autism, the other twin will too, indicating that the disease
probably has a genetic link. But 32 percent of the time one twin will
not have autism. Since twins have identical genetic makeup, that means
some environmental influence is involved in autism as well, Lambert
said.
Scientists also are exploring the relationship between ADHD and toxins
known to interfere with brain development. Rice found that monkeys
exposed in early life to lead and PCBs in amounts similar to what
children often encounter develop learning and behavioral problems that
look remarkably like attention deficit disorder.
PCBs (polychlorinated biphenyls) were widely used to insulate
electrical equipment until it was discovered that they were
accumulating in the bodies of people and animals virtually everywhere
in the world. Although PCBs were banned in 1972, children born three
decades later still have small amounts of the chemical in their
bodies.
"This is not to suggest that ADHD is caused exclusively by neurotoxic
agents in the environment," Rice wrote in an article published in
Environmental Health Perspectives. "However, it seems reasonable to
postulate that environmental neurotoxicants contribute to the
prevalence of ADHD currently being identified in children."
An Environmental Protection Agency report earlier this year identified
ADHD as one of two "emerging issues" in children's environmental
health. Children with ADHD are characterized by having chronic
inattention, impulsive hyperactivity or both to an extent that daily
functioning is impeded.
The second emerging issue identified by the EPA is mercury, a metal
long known to be extremely toxic to the human nervous system. The term
"mad hatter" described the severe effects of mercury used by 19th
century hat makers in Danbury, Conn., to soften felt.
Most Americans have small amounts of mercury in their bodies,
primarily from eating fish. Fish consumption in the United States has
risen sharply since the 1980s, when doctors began urging patients to
reduce beef in their diet to help prevent heart disease.
Tests by the Centers for Disease Control and Prevention show 8 percent
of women of child bearing age have mercury levels in their blood that
exceed the government's safety standard. That means about 320,000
children are born each year at risk for neurological damage from
mercury.
Over the years, scientists have repeatedly lowered their estimates of
how much mercury people can tolerate. The same is true for lead, which
has been known for over a century to cause brain damage.
Two recent studies have concluded that there is no safe level for lead
exposure. Although lead levels in children have dropped dramatically,
government data show that about 90 percent of the nation's children
have between 1 and 10 micrograms of lead in their blood, which means
they are at risk for lowered intelligence.
While the dangers of lead, mercury and PCBs are established,
scientists are also discovering that chemicals with less well
understood effects are widespread in the environment and in people's
bodies.
In 1999, researchers reported finding traces of a widely used group of
flame-retardants known as PBDEs in the breast milk of Swedish women.
In California, state toxicologists saw the Swedish study and decided
to do their own studies. Not only did they find PBDEs in every woman
tested, but the levels were significantly higher than those found in
European women and they were increasing rapidly over time.
Laboratory studies show some PBDEs can alter brain development in mice
during the important brain growth spurt. In humans, the growth spurt
occurs from the last trimester of pregnancy to age 2. The concern is
that PBDEs could have the same effect in children exposed through
their mother's blood during pregnancy and through breast milk after
birth.
Alarmed, the California General Assembly passed a law earlier this
year phasing out the two PBDEs that showed the highest accumulation in
women. Last month, Great Lakes Chemical Corp. of West Lafayette, Ind.,
agreed to cease production of the two chemicals by the end of 2004.
Industry officials contend children are not at risk from the
flame-retardants because levels found in women are too low to pose
harm. They also note that PBDEs are very effective flame-retardants,
saving hundreds of lives every year.
Some scientists see PBDEs as a cautionary tale.
"We came across PBDEs really by chance because we looked for it, found
a strange blip on screen and then it snowballed," said Tom McDonal, a
toxicologist with the California Department of Environmental
Protection.
"There are thousands of chemicals used in commerce and hundreds of new
chemicals introduced each year, many of which we have very little
information on their human toxicity and even less information on
exposures."
(Contact Joan Lowy at LowyJ(at)SHNS.com. Distributed by Scripps Howard
News Service, http://www.shns.com) |
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