Mesothelioma from Natural Sources?

With all the news about ongoing asbestos litigation and corporate malfeasance, it’s easy to forget that asbestos is not a man-made substance. It is a naturally-occurring mineral found in many parts of the world–and exposure to such asbestos can be just as deadly as exposure in the workplace. Before panicking and running down to the local hardware store for a respirator, however, let us put the risk in perspective: as of 2005, statistics showed that the annual death rate in the U.S. from mesothelioma was 2,500. Deaths attributable to secondhand tobacco smoke run about 3,000 per year. In either case, that is far lower than the death rate from heart disease and vehicle accidents, the two leading causes of death in the U.S. The fact is that asbestos has always been present in the environment, and virtually everyone on the planet has suffered exposure to some extent. Asbestiform minerals are found in ultramafic rock formations, which are generally the result of ancient volcanic activity. Asbestos rock is commonly found in the mountains of central and northern California–the Sierra Nevada, the Coast Range and the Klamath Mountains. Human habitation in these areas may go back 5,000 to 10,000 years. Why then the sudden concern? In a word: population.

The hunting-gathering lifestyle of early Indians was very unlikely to disturb the rock. Even mining operations from 1850 onward did not create problems, as gold and silver veins are not usually found in ultramafic deposits. Today however, housing developments are starting to spread up into the foothills where asbestiform minerals lie just beneath the ground. The El Dorado Hills community east of Sacramento is one example. A study of nearly 3,000 California mesothelioma victims diagnosed between 1988 and 1997 showed a strong correlation between the odds of contracting the disease and how far the victim lived from the asbestos source. Not surprisingly, there was little difference between the numbers whether the exposure was the result of a natural outcropping of asbestos or the result of occupational exposure. While the overall mesothelioma rate was 1 in 100,000 in this particular study, the gender difference was striking: men were two and a half times as likely to contract mesothelioma as women. This has since been confirmed by an Australian study. Similar exposure is common in the northeastern Mediterranean countries, specifically parts of Greece and Turkey.