Well
Water Arsenic:
Well
Water Arsenic Levels Linked to Lung Cancer
Residents
of Taiwan who consumed drinking water with high levels of arsenic
have a higher risk of lung cancer, with cigarette smokers from this
group having an even greater risk, according to a study in the December
22/29 issue of JAMA.
Arsenic
is a naturally occurring element in soil, and can contaminate drinking
water, according to background information in the article. Residents
of the southwestern and northeastern coasts of Taiwan had been drinking
well water contaminated with a high concentration of arsenic before
the establishment of the public tap water system.
Chi-Ling
Chen, Ph.D., of the College of Public Health, National Taiwan University,
Taipei, Taiwan, and colleagues conducted a study to determine the
dose-response relationship between ingested arsenic and lung cancer
risk and the added effect of cigarette smoking on this risk.
The
study included 2,503 residents in southwestern and 8,088 in northeastern
arsenic-endemic areas in Taiwan, who were followed up for an average
period of 8 years. Information on arsenic exposure, cigarette smoking,
and other risk factors was collected at enrollment through standardized
questionnaire interview.
During
the study followup period, there were 139 newly diagnosed cases
of lung cancer. Residents with the highest level of arsenic exposure
had a 3.29 times increased risk for lung cancer, after adjusting
for various factors including age, sex, and cigarette smoking status
at recruitment. Among nonsmokers, those who were exposed to the
highest arsenic level had about twice the risk for lung cancer when
compared with those with the lowest level of exposure. Among participants
with the lowest arsenic level, those who had the highest cumulative
cigarette smoking exposure had a 4-fold risk of lung cancer compared
with nonsmokers. When compared with nonsmokers with the lowest levels
of arsenic exposure, those who consumed well water with the highest
arsenic levels and smoked for more than 25 pack-years had a more
than 11-fold risk of lung cancer.
"Approximately
32 percent to 55 percent of lung cancer cases were estimated to
be attributable to the combined effect of cigarette smoking and
ingested arsenic, depending on the levels of both exposures,"
the authors write. "The synergy indices ranged from 1.62 to
2.52, indicating a synergistic effect of ingested arsenic and cigarette
smoking on lung cancer."
"The
reductions in cigarette smoking would likely reduce the lung cancer
risk accompanied by exposure to arsenic, and similarly, reductions
in arsenic exposure would reduce the lung cancer risk among cigarette
smokers. Appropriate public health interventions, such as cigarette
smoking cessation programs and reduction in arsenic concentration
of drinking water, are warranted. Furthermore, it is essential to
take cigarette smoking into consideration in the risk assessment
and the determination of the maximal contamination level of arsenic
in drinking water," the authors conclude.
(JAMA.
2004; 292: 2984-2990. Available post-embargo at www.jama.com)
###
Editor's
Note: This study was supported by grants from the National Science
Council and from the Department of Health, Executive Yuan, Taiwan.
Editorial:
Lung Cancer Etiology - Independent and Joint Effects of Genetics,
Tobacco, and Arsenic
Editor's
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