- WASHINGTON - Blood changes,
including a steep decline in disease-fighting white cells, have been found
in workers persistently exposed to low levels of benzene, a common industrial
chemical known to pose a leukemia risk at high concentrations.
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- Researchers reported Thursday in the journal Science
that workers in a Chinese shoe factory exposed to less than one part per
million of benzene experienced a significant decline of white cells and
found their blood-forming cells were less vigorous than normal.
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- U.S. occupational guidelines limit benzene exposure to
one part per million, but the study found changes in the blood from lower
exposure.
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- "We can't say that this is associated with the future
risk of disease," said Dr. Nathaniel Rothman, one of two senior authors
of the study. "But it does raise the question of what else is going
on in the bone marrow" as a result of low-level exposure to benzene.
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- Benzene also appears to have a toxic effect on the progenitor
cells that form blood cells and that the effect of benzene can be underestimated
if only mature blood cells are studied, said Rothman, a researcher at the
National Cancer Institute, one of the National Institutes of Health.
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- Benzene is one of the most frequently used chemicals
in American industry. It is used as a solvent and to make plastics, resins,
adhesives and synthetic fibers. Workers in shipping, automobile repair,
shoe manufacture and the refining and transportation of oil and gasoline
are routinely exposed to fumes from the sweet-smelling, highly combustible
chemical.
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- In 1987, the Occupational Safety and Health Administration
set the maximum allowable industrial exposure to inhaled benzene at 1 ppm
in eight hours.
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- Rothman said it is too soon to say if that standard should
be changed, but he added that the new study raises concerns about the risks
of low levels of benzene and suggests that more studies are needed to ensure
that American workers are protected.
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- "Biological events are occurring (as a result of
the exposure)," said Rothman. "The question is: What are the
health consequences to the workers?"
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- In the Science study, researchers analyzed blood samples
from 240 workers who were routinely exposed to benzene-laced glue in a
Chinese shoe factory. They compared the results with blood drawn from 140
unexposed workers in a Chinese clothing plant.
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- The researchers also tested the air in the factories
and took urine samples to determine precisely the intensity of benzene
exposure in the two workplaces.
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- They found 109 shoe factory workers who were exposed
to less than 1 ppm of benzene had an average of 15 percent to 18 percent
fewer white blood cells than did workers in the other plant.
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- Researchers also discovered that the blood progenitor
cells in the shoe factory workers were less able to grow and reproduce
than were such cells taken from the clothing workers.
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- Dr. Gilbert Omenn of the University of Michigan Medical
School said in Science that the study "should cause a stir in the
occupational and environmental health circles."
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- Bill Perry, director of the Office of Chemical Hazards
at the Occupational Safety and Health Administration, said the current
benzene standard was developed "after more than a decade of extensive
research and a comprehensive regulatory process."
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- He said the study in Science has not yet been reviewed
and "evaluation will take some time."
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- Officials from the Environmental Protection Agency did
not respond to requests for comment.
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- The study is a subset of a larger benzene study, now
under way in China, that was prompted by concerns among scientists there
that the chemical might increase leukemia among workers.
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- Dr. Martyn T. Smith of the University of California,
Berkeley, was the second senior author. Other co-authors included those
from the Chinese Center for Disease Control and Prevention; the University
of North Carolina, Chapel Hill; the New York Blood Center, White Plains,
and the Peking Union Medical College in Beijing.
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- Copyright © 2004 The Associated Press. All rights
reserved. The information contained in the AP News report may not be published,
broadcast, rewritten or redistributed without the prior written authority
of The Associated Press.
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- http://news.yahoo.com/news?tmpl=story&u=/ap/2004
1203/ap_on_he_me/benzene_exposure
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