Lung damage in cotton workers partly reversible
NEW YORK (Reuters Health) - Workers in the cotton textile industry
often develop chronic coughs and other respiratory problems, but a
new study suggests that their lung function typically improves
after retirement.
Working with cotton exposes people to dust and endotoxin, a
substance produced by bacteria that can trigger inflammation in the
airways. It's known that workers in the industry have increased
rates of breathing problems, including chronic cough and chronic
bronchitis -- persistent inflammation in the lungs that causes
symptoms like breathlessness and wheezing. However, it has been
unclear whether those effects are at least partly reversible.
In the new study, reported
in the American Journal of Respiratory and Critical Care Medicine,
researchers followed 447 Chinese men and women working in the
cotton textile industry, along with 472 workers in the silk
industry -- where workers are not exposed to high levels of
endotoxin.
Over 25 years, the researchers periodically measured the workers'
lung function using a standard test that gauges the amount of air a
person can forcibly exhale in one second. They also questioned the
workers about any respiratory symptoms.
Overall, the study found, cotton workers' lung function improved
after retirement, particularly within the first 10 years.
What's more, their rates of certain respiratory problems declined
over time. At the start of the study in 1981, 21.5 percent of
cotton workers had chronic bronchitis, and a similar percentage had
chronic cough. Fifteen years later, those figures were 5 percent
and 2 percent, respectively.
In addition, the rate of byssinosis -- a lung disease specifically
linked to on-the-job exposure to cotton dust -- declined from 8
percent to less than 2 percent.
The proportion of cotton workers reporting bouts of breathlessness
increased over time -- from 15 percent to 20 percent. But that rate
also increased among silk workers, from 4 percent to 14 percent,
and such effects can be related to aging.
Overall, the findings suggest that the lung damage from working in
the cotton industry is partially reversible, according to the
researchers, led by Dr. Jing Shi of the University of Science and
Technology in Beijing. "Partially," they note, because, on average,
cotton workers' lung function did not reach that of silk workers
after retirement.
Shi's team also found that cotton workers who smoked suffered
greater effects on lung function than non-smokers during their
working years. But they also improved more rapidly than non-smokers
did after retirement.
As for the silk workers in the study, their lung function also
generally improved after retirement.
Similarly, their rates of chronic cough and chronic bronchitis,
while always lower than those of cotton workers, also dipped (from
just under 8 percent to 6 percent for bronchitis, and from 7
percent to 3 percent for chronic cough).
The reason for that, Shi's team writes, is not entirely clear, as
silk workers were not exposed to cotton dust or higher-than-normal
endotoxin levels. Some other, "unmeasured exposure," according to
the researchers, may have affected silk workers' lung health.