Kids 'n' the
Environmental Health Sciences:
FINDING WAYS
TO HELP A 'VULNERABLE POPULATION'
 The cliche is true: Children are our future.
And, besides, we love 'em. Both statements are good reasons to
focus considerable medical research on kids.
But there is an important
additional reason for such a focus in health research related
to the environment: The growth, development and rapidly reproducing
cells of fetuses, infants, toddlers, older children and teens
make them particularly susceptible to environmental insults.
Thus, the effects on children of lead, chemical dump sites,
pesticides, PCBs, benzene, environmental estrogens and both
outdoor and indoor air contaminants are a particular focus of
environmental health research. We want to know what substances
can cause problems, how to spot susceptible kids -- and how
to intervene to prevent illness.
Here are some samples:
LEAD POISONING
-- At high doses, lead (commonly found in old paint, household
dust, soil, pipe solder and some ceramics) has long been known
to cause severe health problems -- muscle and abdominal pain,
mental symptoms, paralysis and even death. Until recently, however,
we have not appreciated the devastating effect of low exposures
early in life.
Basic research has
shown the adverse effects of lead on children's IQ and physical
development at levels previously considered safe. Based on these
and other findings, public health officials declared lead the
#1 environmental hazard to American children and the federal
Centers for Disease Control and Prevention lowered what is considered
to be "acceptable" blood lead levels.
Research has helped
to show the sources of lead in the environment and to design
public health prevention efforts, as well as treatments to remove
lead from affected children, a process called chelation.
To help improve this
treatment, NIEHS supported the study of dimercaptosuccinic acid
(DMSA). Known generically as Succimer and trade-named Chemet,
it has the advantage over previously used intravenous therapies
that it can be given by mouth, without hospitalization.
Succimer is approved
by the Food and Drug Administration for use at lead levels above
45 micrograms per deciliter of blood. However, a treatment may
be needed for even lower lead concentrations, because there
are measurable effects between 10 and 25 micrograms per deciliter.
- To meet this need,
NIEHS is conducting a clinical trial to test Succimer in children
whose blood lead concentrations are within this lower range.
Inner-city hospitals are participating in this trial in Cincinnati,
Ohio; Newark, N.J., Philadelphia, Pa., and Baltimore, Md.
The National Institutes of Health's Office of Research on
Minority Health also is helping to support this trial. The
aim is to see if oral chelation reduces or prevents lead induced
developmental delay. Eight hundred kids are now being followed.
Additionally:
- Recent studies
supported by NIEHS suggest that a young person's lead burden
is not only linked to lower IQS and lower high school graduation
rates but to increased delinquency.
- Preliminary data
from two other grantees' studies indicate that girls exposed
to lead store the metal in their bones. This lead can be released
when they become pregnant years later, exposing their fetuses.
NIEHS continues to perform
and support research on lead's effects. The research is important
in its own right and because lead may represent a model
of how other environmental hazards can hurt the fetus or developing
child and adolescent, even at relatively low levels of exposure.
For example:
PCBs AND INTELLIGENCE
-- Reduced intelligence also results from another common contaminant,
polychlorinated biphenyls, or PCBs. Partly as the result of
NIEHS studies, PCBs have been barred from their past uses in
electric transformers, paper recycling and other commercial
processes. But they are stable, persistent compounds that remain
wide-spread in the environment and, being fat soluble, concentrate
in animal foods and in the people eating these foods.
NIEHS studies have
shown that nursing mothers can transfer their own internal supply
of PCBs to their infants through breast milk or, earlier, to
the developing fetus. Fetal exposure translates into lower
IQ, poor reading comprehension, memory problems and difficulty
in concentration -- good reasons for the FDA and state advisories
warning against women of child-bearing age and children under
15 to avoid fish taken from contaminated waters.
In one follow-up,
the University of Albany is studying the exposure PCBs and subsequent
physical, mental and behavioral growth of 400 Mohawk children,
10 to 16.
NIEHS' scientists
have also studied 117 offspring of women poisoned by PCBs in
a 1979 food contamination in Taiwan. The PCBs were heat-degraded
and thus partly converted to polychlorinated dibenzofurans (PCDFs).
The children show such defects as carious teeth, poor nail formation
and short stature. They average worse for conduct and hyperactive
behavior and have persistent developmental delay averaging 5
to 8 points on standard IQ scales. The delay is as severe in
children born up to six years after exposure as it was for those
born in 1979.
CHILDHOOD ASTHMA
AND OTHER LUNG PROBLEMS -- Asthma affects up to 20 million
Americans. Its prevalence and severity appear to be increasing
among children, particularly Hispanics of Puerto Rican origin
and African Americans.
The benefits from
emission controls on motor vehicles have been very nearly negated
by increases in the numbers of our cars and trucks. And the
use of tall stacks to disperse sulfur dioxide from large coal
burning plants, while reducing sulfur dioxide at ground level,
has increased the proportion of sulfur dioxide that is converted
into sulfuric acid within the air, so acid aerosol concentrations
have not declined much in recent years.
Chronic exposure
to these current levels of acidic aerosol has been associated
with respiratory symptoms in children. Environmental health
scientists are concerned that acidic aerosol can trigger acute
asthmatic reactions and, often, result in hospitalization.
- For many years,
the NIEHS has funded the Six Cities and 24 Cities studies
at the Harvard University's Kresge Center for Environmental
Health. The studies have shown a strong and consistent relationship
between elevated indoor concentrations of oxides of nitrogen
and lower respiratory tract symptoms.
- Recent findings
also suggest that exposure to sulfur dioxide, particulate
matter and acid aerosols (in urban (outdoor) air) is associated
with bronchitis in children.
- A related study
is assessing the degree of risk of minority and/or disadvantaged
children from such things as air contaminants from kerosene
heaters.
ESTROGENS IN MEDICINE
AND PESTICIDES -- NIEHS studies helped show the effects
on the children of women who took the potent synthetic estrogen
DES in pregnancy to prevent miscarriage. NIEHS and other research
organizations have done many studies of pesticides -- including
those containing chemicals that may mimic estrogens or disrupt
the "chemical message system" of the body's hormones during a
child's development.
DDT was banned when
estrogenic effects were observed -- such as the thinning of
the eggshells which threatened the survival of the Bald Eagle.
But what of DDE, the form of DDT that persists in the environment?
The Institute's scientists followed more than 700 North Carolina
children exposed to DDE in breast milk and found no related
illness or lasting developmental abnormality. However, the women
with the highest levels of DDE in their milk breast-fed their
children less than 40 percent as long as women with lower levels.
A study in Mexico, where DDE in milk was often higher, showed
a similar decrease in length of lactations, at least among second
and later children. This may be related to the estrogenicity
of DDE, since even very low doses of contraceptive estrogens
can interfere with milk production.
Despite the research
that has been done by NIEHS and others, the prestigious National
Academy of Sciences says in the recent report "Pesticides in
the Diets of Infants and Children" that there remains a knowledge
gap as to the possible effects of pesticides on the development
of the immune, nervous and reproductive systems from fetal,
newborn and childhood exposures.
The academy recommended
a significant research effort regarding these and other possible
effects.
In one response,
NIEHS is conducting a complex series of experiments with experts
from the Environmental Protection Agency's Health Effects Research
Laboratory. The experiments, which will require three years,
will evaluate the effects in generations of rodents of common
pesticides about which the academy expressed particular concern:
carbaryl, parathion, chlorpyrifos, atrazine and trichlorfon.
CHILDHOOD LEUKEMIA
-- Clusters of childhood leukemia appear to occur around hazardous
waste facilities, including Superfund sites. Studies supported
by NIEHS at the University of California-Berkeley are attempting
to determine what environmental exposures, including tobacco
smoke and poor diet, may lead to leukemia and how to identify
those at risk.
A relatively new
technique called fluorescence in situ hybridization,
or FISH, has shown for the first time that people working with
benzene, a chemical in gasoline, develop chromosome aberrations
specifically related to leukemia. This work was conducted in
China, but the same UC-Berkeley team has recently demonstrated
that FISH can detect these markers of leukemia risk in children
in a low socioeconomic area of the San Francisco Bay area.
This work is being
supported by the Superfund Research Program, which NIEHS administers.
'MOST VULNERABLE
POPULATION' REQUIREMENTS -- The above research on PCBs
and lead and other substances led Congress to require in the
new Food Quality Protection Act and in reauthorizing other regulatory
law such as the Clean Water Act that the population "most vulnerable"
to a substance must be identified and that risk assessment and
regulations must be based on that population.
Building on the results
of this conference, and on a base of intramural and grantee
accomplishments recognized by two recent Nobel Prizes, NIEHS
will continue to use its available resources in the pursuit
of research to help more children develop their full potential
as healthy and intelligent adults.
National
Institute of Environmental Health Sciences
National
Institutes of Health
Fact Sheet #5 - KIDS
-- 2/97 |
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