Evidence of chemical effects on children mounts

[Guest guest]

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.

 

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16-03