Chemicals replace microbes as
top health danger, scientist says
By JEFF FRANKS
HOUSTON Chemicals have
replaced bacteria and viruses as
the main threat to human health in
Western industrial nations, accord-
ing to a Texas A&M University
"Most of the major causes of
death in the Western world up
until the 1950s were mainly dis-
eases of microbial origin influ-
enza, pneumonia, tuberculosis.
Through public health practices,
immunization and nutrition, we've
just about controlled those," toxi-
cology professor Rick Irvin said.
"The diseases we're beginning
to see as the major causes of death
in the latter part of this century
and certainly into the 21st century
are diseases of chemical origin,"
Irvin said scientists now be-
lieve 70 to 90 percent of all can-
cers, for example, are caused by
exposure to chemicals.
Heart disease, too, is essential-
ly chemical in origin because it is
caused by fatty foods and cigarette
smoking, Irvin said.
"When you're talking about di-
et and cigarette smoke, you are
talking about chemicals," he said.
Heart disease and cancer are
responsible for more than 50 per-
cent of all deaths in Western na-
tions, Irvin said.
Toxic chemicals may work sin-
gly or in combination with other
chemicals to cause disease, he ex-
"We're finding that with a lot
of combinations, we get a toxic
effect not previously known," Irvin
For example, he said, it has
been found that diesel soot has as
many as 100 chemicals in it, many
of which combine to create the
same carcinogens found in ciga-
Irvin believes the threat posed
by toxic chemicals will grow be-
cause researchers are producing
more and more new substances for
industrial and scientific use.
"We're getting a lot more of
what I call high-tech chemicals -
such as those used in the manufac-
turing of microelectronics that
have very specialized uses. We re-
ally don't know much about this
group and its effect on humans,"
Irvin said people cannot avoid
all chemicals, but they should use
common sense to avoid excessive
exposure to harmful substances.
Personal habits can go a long way
toward assuring a full life, he said.
"For example, I don't smoke or
drink and I don't take illegal drugs.
I eat a high-protein, low-fat diet
and I expect to live my three score
and 10 years," he said.
A person's genetic makeup in-
fluences his or her susceptibility to
disease, but it appears that genes
"modulate as opposed to deter-
mine" the amount of risk, Irvin
"Some people, because of their
genes, are more likely to get dis-
ease from chemicals than others,
but their genes will not absolutely
determine their fate," he said.
"If life were a football field and
the opposite end zone were cancer,
some people would start on the
30-yard line, while others would be
back at the goal line with less
chance of getting the disease be-
cause of their genes," Irvin ex-
He also said that while chemi-
cals pose a threat to health, in
some ways they are less insidious
than bacteria and viruses.
It is difficult to completely wipe
out disease-carrying microbes be-
cause they can be transmitted to
other humans. Chemicals, on the
other hand, generally cannot be