a pbs.org report on
BILL MOYERS' POLLUTED BODY
_____________
As
part of a study of pollutant loads in the human body sponsored
by the Mount Sinai School of Medicine in New York, samples of
Bill Moyers' blood and urine were analyzed. Eighty four distinct
chemicals were found.
His
test results -- much like a chemical fingerprint – revealed
evidence of hazardous chemicals in common use -- as well as
compounds banned for more than a quarter century -- and others
so obscure that almost no public information is available to
identify what products might have resulted in Moyers' exposure.
The
results are not unusual. Each of us has some load of industrial
chemicals stored in or passing through our bodies. These chemical
residues -- termed the ‘chemical body burden’ --
can be detected in blood, urine and breast milk. Most people
are unaware that they carry chemical compounds in their bodies.
The
health effects of chronic exposure to low levels of chemicals
are only beginning to be studied. In addition, scientists have
never assessed the effects of exposures to the endless combinations
of chemicals found in people. The potential health effects discussed
are based on persuasive evidence from studies of laboratory
animals and wildlife, as well as some evidence from human studies.
Much
of our scientific knowledge about the health effects of chemicals
comes from laboratory studies of animals. While humans are not
necessarily susceptible to all of the diseases that chemicals
cause in test animals, there are many similarities between the
way humans and other species respond to toxic exposures. Former
U.S. Assistant Surgeon General David Rall noted that every chemical
known to cause cancer in humans also causes cancer in experimental
animals. While some species are more sensitive to toxic effects
than others, Rall wrote, laboratory studies have proved to be
good predictors of health effects in humans.
Fundamental
biological systems are remarkably similar in all mammals, and
-- at the cellular and biochemical level -- most species respond
to toxic substances in similar ways. Based on years of comparative
studies, biologists believe that many of the health problems
observed in animals could also occur in people at some exposure
level. However, conclusive proof is often elusive. Since researchers
cannot ethically dose humans with suspected toxicants, they
must rely on studies of people accidentally poisoned or exposed
in the workplace. The normal variables of human life make such
studies less than scientifically ideal. For instance, workers
may be exposed to multiple chemicals, or poisoning victims may
have smoked cigarettes, confounding efforts to assess the damage
done by a single chemical. But combined with animal studies,
this epidemiological research has provided enough evidence to
raise concerns about many chemicals in common use.
Sorting
out the health effects of low level exposures may be the most
difficult task of all. Because most toxicity studies look at
people exposed in the workplace, where exposure levels are much
higher than what most of the world's population would see, the
health effects of the average levels of chemicals found in people
are largely unknown. However, according to Dr. Michael McCally
of Mt. Sinai, the study's lead doctor, "Current 'normal'
body burdens of dioxin and several other organochlorines in
humans are at or near the range at which toxic effects occur
in laboratory animals."
Research
has made one thing clear -- there is tremendous variability
between individuals in their responses to toxic substances.
Even the highest level exposures will not make everyone sick.
Among workers with similar exposures to vinyl chloride, for
example, one might be stricken with a brain tumor, another with
liver cancer, and a third with bone disease -- but no cancer
at all. Still others may remain completely healthy. On the other
hand, people with far lower exposures may also suffer health
problems.
The
Environmental Protection Agency acknowledges that some groups
of people are far more susceptible to toxic effects than others.
Children are among the most vulnerable. It is known that women
pass some of their body burdens to their children during pregnancy.
Most scientists concur that exposures in uterus and in early
childhood pose far greater risks than exposures later in life.
