Minimal Exposure
to Asbestos-like Fibers Affects Lungs
[Posted 03/21/2008]
A study found that men and women who worked in a
plant that processed vermiculite tainted with
asbestos-like fibers that originated from a mine in
Libby, Montana, show high prevalence of scarring and
thickening of the membrane that lines the chest wall
some 25 years after the plant stopped using the
material — even those who were exposed at or below
current legal levels.
In 1980,
researchers examined 513 individuals who worked at
a plant that processed Libby vermiculite and found
pleural changes or interstitial fibrosis in 2.2% of
the overall cohort. In a follow-up study, a
research team led by James Lockey, MD, the
principal investigator of the 1980 report, found
that the unadjusted prevalence in the still-living
members of the original cohort was 28.7% for
pleural changes and 2.9% for interstitial fibrosis.
Lockey had expected to see a higher rate of change
over time, but was surprised at the percentage.
The
findings indicate that
“a significant number of
workers exposed at the current limit would
experience pleural abnormalities,” wrote Gregory
Wagner, MD, of NIOSH, in an accompanying editorial.
Furthermore, regulations governing legal exposure
limits to hazardous materials apply only to
specific fibers, not to all types of fibers that
have similar and predictable biological effects.
Perhaps
most importantly, the research highlights the need
to anticipate the health implications of
occupational exposures.
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