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Scientific News  Ecology LOW LEVELS OF BENZENE DAMAGE HEALTH
LOW LEVELS OF BENZENE DAMAGE HEALTH
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Even low levels
of benzene may place factory workers at risk.
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Punchstock |
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A study of Chinese
factory workers has shown that exposure to the chemical benzene destroys several
types of blood cell. The effects are seen even at levels below the current US
legal exposure limit of 1 part per million.
Benzene, which is used as an industrial solvent
but also found in cigarette smoke and vehicle exhausts, has long been linked to
the blood disease leukaemia. This study shows that even low levels of the
chemical can damage the blood system.
The study was carried out by Martin Smith of the
University of California, Berkeley, along with colleagues based in the United
States and at the Chinese Center for Disease Control and Prevention in Beijing.
They spent 16 months tracking 250 workers in a shoe factory near Tianjin who had
varying exposures to benzene. They compared their blood-cell counts with those
of workers from a nearby clothes factory, where no benzene was used.
Workers exposed to benzene showed reduced counts
of white blood cells and platelets, the researchers report in this week's Science1.
"It will be important to examine the long-term health effects in workers
exposed to low levels of benzene, such as increased occurrences of serious
diseases of the blood system including leukaemia," add the researchers.
Early damage
Workers exposed to the highest levels of benzene,
over 10 parts per million (ppm), had around 24% fewer white blood cells than
their counterparts in the clothes factory, the researchers report. And even
those exposed to less than 1 ppm showed a drop of around 15%.
Cell counts were reduced in a wide range of
white blood-cell types, including cells called granulocytes, lymphocytes and B
cells. Because of this, the researchers suspect that benzene may be damaging the
precursor cells that divide to give rise to these different cell types.
In blood samples from 29 benzene-exposed workers,
those with the greatest exposure showed the biggest reduction in precursor-cell
counts, suggesting that benzene does indeed affect these growing cells. Workers
in the study were not found to be exposed to any other solvents, and benzene
exposure outside the workplace was negligible.
The researchers also identified two genetic
variants that may accelerate the damage caused by benzene. Those with certain
versions of two particular metabolic enzymes, which are thought to convert
benzene into more harmful compounds, suffer lower cell counts.
Active harm
People with more active versions of these
enzymes are more susceptible to harm, suggests Nathaniel Rothman, a member of
the study team based at the US National Cancer Institute in Bethesda, Maryland.
"More than 50% of the general population seem to have a variant associated
with high activity," he adds.
Despite the fact that benzene is spewed out from
car exhausts, we shouldn't necessarily be worried about walking the urban
streets, Rothman says. Typical benzene levels in polluted cities are a few parts
per billion, far below the levels found in the Chinese shoe factory.
Nonetheless, Rothman would like other
researchers to try and replicate his team's results, to confirm the health
dangers and, if necessary, revisit the legal safety limits. "One study
doesn't change regulations," he says. "But as more data are generated,
people who deal with risk and policy will be able to use them."
References
- Lan Q., et al. Science, 306. 1774 - 1776 (2004). | Article |
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©
Nature News Service
Publishing date: December 24, 2004
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