Coal, cancer, silica- and global mass extinction

Excellent Wired article, via Highly Allochthonous (which references the far-from excellent Fox News version of the story here).

In a nutshell: a new paper published in December’s Environmental Science and Technology suggests that the high incidence of lung cancer in the women of Xuan Wei county, China, is due to the high silica and volatile content of the coal used in indoor (and unventilated) stoves in the region. This coal is believed to derive its high silica content from the effects of the catclysmic Permian-Triassic extinction event 250 million years ago, when acid rain (a result of the flood basalt eruptions proposed as a cause of the extinction) accelerated the chemical weathering of surface rocks. The resistant silica residue from this weathering accumulated in peat deposits, which were later transmogrified into the region’s coalfields.

The basic hook of the story is “Earth’s greatest ever extinction event is still claiming lives 250 million years later”. It’s an unsettling and thought-provoking idea, but one that somewhat overshadows the big issue here, and the principal reason the research was commissioned in the first place: the debilitating and still under-appreciated effect of indoor air pollution on health in the developing world, and in rural China in particular. To be fair, both articles mention this- even the geologically-illiterate Fox story- although the wording is largely lifted from the original paper’s press release and relegated to the ‘skip-this-part-if-you-don’t-have-time’ latter sections.

Passing over the admittedly intriguing geo-stuff, the role of silica in all this is interesting from a medical point of view. There’s a well-established occupational disease called ‘silicosis’, suffered by stonemasons and other rock-cutters, in which inhaled silica particles induce pulmonary fibrosis and a potentially devastating loss of lung capacity. I’d never heard of silica causing cancer though, and it seems that the role of silica as an independent risk factor for lung cancer has yet to be definitively proven, although evidence for this does seem to be accumulating. The recent paper throws a new idea into the mix: that it’s the combined effect of the high silica content and the high levels of volatiles in this particular coal type that increases cancer risk, rather than either of these factors individually.


One Response to “Coal, cancer, silica- and global mass extinction”

  1. cho-cho Says:

    Great post. I got new perspective after read this article.


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