TOXIN DEBATE: Accumulate in body ... or Not????

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TOXIN DEBATE: Accumulate in body ... or Not????

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 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 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 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. "