Global Challenges/Chemistry Solutions

Combating disease: Coal from mass extinction era linked to lung cancer mystery

April 26, 2010


Coal from China’s Xuan Wei County, widely used
for cooking and heating, may contribute to unusually
high rates of lung cancer among women in the region.
Credit: U.S. Department of Energy.
(High-resolution version)

  Summary

For years, women in China’s Xuan Wei County in Yunnan
Province — women who never smoked cigarettes — have
been plagued by lung cancer. The mortality rates among
female nonsmokers are the world’s highest — up to 20
times higher than average in China. A new study sheds
light on the cancer epidemic and points to an unlikely
source: volcanic eruptions occurring millions of years ago.

For years, women in China’s Xuan Wei County in Yunnan Province — women who never smoked cigarettes — have been plagued by lung cancer. The mortality rates among female nonsmokers are the world’s highest — up to 20 times higher than average in China. A new study sheds light on the cancer epidemic and points to an unlikely source: volcanic eruptions occurring millions of years ago.

These cataclysmic events 250 million years ago are believed to be responsible for Earth’s largest mass extinction as they killed more than 70 percent of plants and animals. Today the remnants of the volcanic activity are still taking lives, according to a new study in ACS’ Environmental Science & Technology.

The study shows that high-silica content of coal, which formed long ago from those massive volcanic eruptions, may now be interacting with other substances in Xuan Wei County’s coal to cause the elevated rates of lung cancer.

For more, here’s Dr. David Large, the study leader and professor of Chemical and Environmental Engineering at the University of Nottingham in the United Kingdom:

“Those same events that happened 250 million years ago that almost erased all life are still causing major problems today in south China. We believe the single property that makes this region’s coal unusual is its high concentration of very fine silica.”

Earlier studies link volatile substances in coal smoke called polycyclic aromatic hydrocarbons to lung cancer in Xuan Wei County, where women heat their homes and cook on open coal-burning stoves that are not vented to the outside. Scientists believe indoor emissions from burning coal cause cancer, but it was unclear before now why lung cancer rates in this region of China are so much higher than other areas.

Large and colleagues found that coal used in parts of Xuan Wei County had about 10 times more silica, a suspected carcinogen, than U.S. coal. The silica-enriched coal in the region was likely a result of the volcanic eruptions, Large says, which created acid rain that dissolved surface rocks to release the silica. Silica now may be working in conjunction with polycyclic aromatic hydrocarbons to make the coal more carcinogenic.

Here’s Dr. Large on the considerable dangers facing the region:

“A typical household in Xuan Wei County consumes about three to eight tons of coal each year. So in that period a family could handle a half-ton of fine-grained silica particles, which has recently been classified a carcinogen. The potential health effects of it can’t be ignored.”

Smart Scientists/Innovative Thinking

Smart chemists. Innovative thinking. That’s the key to solving global challenges of the 21st Century. Be sure to check our previous podcast episodes on combating disease. Today’s podcast was written by John Simpson.
For the American Chemical Society, I’m Adam Dylewski in Washington.