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Environment
and Disease
Questions and
Answers
Q.
What percent of the 1,700 pounds of chemicals that are manufactured
annually for each of us is composed of carcinogens?
A. We simply
do not know. There are 50,000 chemicals in commercial production.
It is estimated that about 10,000 are in significant commercial
production and perhaps 2,000 present significant exposure levels.
We do not know what fraction of those have been adequately tested,
but certainly it is not much more than 10 to 30 percent.
We are starting a
literature study in an attempt to estimate how well these widely
used compounds have been tested. This study probably will require
two or three years to complete, but when completed, it should
provide the answer to your question.
Q.
About five years ago there was great concern that DES-exposed
daughters would develop cancer. What are the chances that this
disease will develop in 10 or 20 years in a DES-exposed daughter
who does not have cancer now?
A. An extraordinarily
large number of women were exposed to DES. Although a fair number
of their daughers did develop cancer, the actual risk to any
one person does not seem very great at all, perhaps one in thousands.
Q.
Would you mention some of the other chronic diseases that may
be caused by chemicals?
A. There is
some evidence that certain chronic kidney diseases have a chemical
origin. Chronic glomerulonephritis, a major social problem in
the United States today, may occur more frequently if there
has been exposure to a volatile solvent just before the initiating
infection. Many liver diseases are associated with chemicals.
For example, vinyl chloride causes a very severe chronic liver
disease.
Chloracne is one
of a number of chronic skin diseases related to chemical exposure.
In addition to pulmonary problems caused by cigarette smoking,
many of the pulmonary fibroses are caused by inhalation of toxic
chemicals. A final example is the association of a type of diabetes
with exposure to a pesticide.
Q.
Have mental or emotional disorders been linked to chemical exposure?
A. Not that
I know of.
Q.
Do you think that screening techniques like the Ames Test will
be effective in the future?
A. I think
they will be terribly important in the future. Many investigators
believe that most cancers originate in a mutation or change
in a cell's basic genetic material. The mutation causes the
genetic material, also known as DNA, to give a wrong signal
to the next generation cell. Most chemical carcinogens cause
such mutations or changes in DNA. During the last 5 to 10 years,
scientists have developed a number of very simple tests using
mammalian cells grown in tissue culture which can very rapidly
and cheaply identify these mutations. "Informal" studies have
shown that there is quite a good correlation rate between the
ability to produce mutations in these tests and the ability
to cause cancer in animals. At the moment, however, these tests
are very new. They have not been validated. We do not know if
they are reproducible and predictable. Under the National Toxicology
Program, hundreds of chemicals will be tested for mutational
activity to determine if the Ames Test is reproducible and if
it predicts for carcinogenicity in laboratory animals or in
man. Screening techniques like the Ames Test will make an enormous
difference in the future; but it is a little premature to use
them now.
Q.
After asbestos was identified as a carcinogen in people, asbestos
ceiling tiles were removed from many school buildings. Should
I replace the asbestos roof on my house?
A. Although
asbestos is a nasty fiber, sheets of flooring or roofing material
containing asbestos are considered safe since the fibers are
embedded in cement or plastic.
Asbestos is considered
very dangerous when the material hangs loose and dust can be
produced when the asbestos is hit or manipulated.
Q.
Have asbestos mines been closed?
A. No, asbestos
continues to be mined and sold.
Q.
Who is alerting the public to the dangers of these chemicals
that are discovered to be carcinogenic?
A. The National
Institute of Environmental Health Sciences and the National
Cancer Institute have some public awareness programs.
In addition, the Environmental Defense Fund and the National
Resources Defense Council have very aggressive programs
Q.
Do you think it is inadvisable to eat tuna fish since it could
contain a concentration of whatever chemicals are found in the
water?
A. It does
not seem like that is a problem. There was the methyl mercury
scare in the early 1970's; however, based on current knowledge,
the levels in tuna fish essentially safe. l think tuna fish
probably is about as good a food as any.
Q.
Do you have any opinion about calcium propionate or any of the
other preservatives found?
A. Not specifically.
Most preservatives have been tested and those that were inadequately
tested are being retested.
Q.
Is cyclophosphamide used in the treatment of some forms of breast
cancer?
A. Yes. And
it is a very effective anti-cancer drug. However, it is also
a carcinogen.
Q.
Are asbestos plates used under pots to prevent food from bubbling
over or burning dangerous?
A. I think
that most scientists used exactly the same as pads on their
Bunsen burners. There is relatively little fiber release from
those pads. Probably it is prudent not to use them, but they
are not the type of major hazard I would worry about. In addition,
the Environmental Defense Fund and the National Resources Defense
Council have very aggressive programs.
Q.
Do you think it is inadvisable to eat tuna fish since it could
contain a concentration of whatever chemicals are found in the
water?
A. It does
not seem like that is a problem. There was the methyl mercury
scare in the early 1970s; however, based on current knowledge,
the levels in tuna fish essentially are safe. l think tuna fish
probably is about as good a food as any.
Q.
Do you have any opinion about calcium propionate or any of the
other preservatives found in foods?
A. Not specifically.
Most preservatives have been tested and those that were inadequately
tested are being retested.
Q.
Is cyclophosphamide used in the treatment of some forms of breast
cancer?
A. Yes. And
it is a very effective anti-cancer drug. However, it also is
a carcinogen.
Q.
Are asbestos plates used under pots to prevent food from bubbling
over or burning dangerous?
A. I think
that most scientists have used exactly the same asbestos pads
on their Bunsen burners. There is relatively little fiber release
from those pads. Probably it is prudent not to use them, but
they are not the type of major hazard I would worry about.
Q.
What is happening to towns like Hopewell, Virginia? Do they
continue to develop their chemical industry? How can we be protected
from incidences like those that happened in Hopewell and Love
Canal?
A. Hopewell
is a chemical industry town and apparently is growing. The plant
that caused the kepone problem has been closed and dismantled
as a result of effective legal action.
We simply do not
know enough about toxic chemical waste dumps as epitomized by
Love Canal. Perhaps 200 chemicals can be found in Love Canal.
There is intense Congressional activity to develop legislation
to deal with this major problem and clean up these old dumps.
Since new regulations
on dumping are much more restrictive, most problems do not develop
in the dumps being used today, but primarily involve those older
dumps that were used and then forgotten. l believe that toxic
chemical waste disposal will remain as one of our major problems
for the next three or four years.
Q.
There is considerable concern today about the chronic health
hazards of radiation. Would you consider chemicals to be an
equal health hazard?
A. I do not
pretend to be an expert on radiation and I think it is difficult
to make that sort of comparison.
Radiation and chemicals
are both very serious problems. Radiation is much better controlled
in the United States than carcinogenic chemicals.
Consequently, I think
that, currently, chemicals may be a much larger problem. But
that is a very unscientific estimate.
Q.
How large an increase in cancer incidence would be necessary
before a chemical could be identified as a problem?
A. Many studies
have pointed out the weaknesses of epidemiology. For example,
a New York University group conducted a study on breast cancer
and users of hair dyes.
In this fairly large
study, researchers found a doubling of the incidence of breast
cancer among those women using hair dyes who had low natural
susceptibility to breast cancer. This finding was barely statistically
significant, right at the borderline, yet this relationship
could cause literally tens of thousands of additional cases
of breast cancer.
In addition, this
study only went back 15 years. Based on our knowledge of other
carcinogens in the human population, after 15 years we just
begin to see the effects of chemical exposure. Unfortunately,
that is the best answer I can give to your question.
Q.
It is very clear to me that animal studies will have to be used
to determine the approximate levels of permissible exposure to
a chemical in our environment.
How
do we relate the doses used in animal studies and the length
of time required for a tumor to develop in animals to the same
situations in humans?
Do
we know how to translate 143 days in a mouse into years in a
human being?
A. You bring
up a very good question. Exprapolating from animal studies,
a heavy cigarette smoker has a 50/50 chance of developing lung
cancer in about 145 years.
The time required
to develop a tumor is a surprisingly insensitive way of analyzing
research results.
The disparity between
a mouse and a man makes us uncomfortable about comparisons,
but the empiric evidence suggests that we should not be as uncomfortable
as we might intuitively feel.
Q.
What suggestions do you have for workers who suspect that working
conditions may be impairing their health?
A. Under a
provision of the Occupational Safety and Health Act of 1971,
workers can ask for a health hazard evaluation from the National
Institute for Occupational Safety and Health (NIOSH).
Any worker with concerns
about his or her working conditions can contact NIOSH for more
detailed instructions for requesting such an evaluation.
Q.
Is cigarette smoking more dangerous at particular ages?
Do
older people have fewer defenses to protect them from the effects
of smoking than someone in their 20's or 30's?
A. Cigarette
smoking is basically bad. It is worse if you are pregnant. If
an individual starts smoking at age 60 or 70, he or she probably
is in good shape because of the time required for a tumor to
develop.
Since it might take
30 or 40 years for the tumor to develop, cancer may not be very
important to a person 100 years old.
Q.
Are there any toxic effects from the production of manmade
fibers or their use in clothing?
A. Although
it has been observed that we are seeing an increasing amount
of sunlight-induced skin cancer because of the light weight
and skimpy clothing our society wears, l do not think that the
ingredients of our clothing present dangers. The people at greater
risk from these artificial fibers are the workers who produce
the raw materials, the workers who initially manufacture the
fibers, the people who live downstream of the manufacturing
plant, and the people who may live near a dump receiving fiber
residue.
Once the fibers are
locked in place in cloth, they are relatively harmless.
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