By David Michaels

NIOSH scientist Patricia Sullivan has just published a very important study that reminds us (as if any reminder were needed) that there really is no safe level of asbestos exposure.

The study looked at the causes of death among workers involved in mining, milling and processing asbestos-containing vermiculite in WR Grace’s plant in Libby, Montana. Dr. Sullivan found increased risk of lung cancer among workers whose lifetime asbestos exposure was only slightly higher than they would receive working a lifetime at the current OSHA standard.

A little background: Vermiculite is widely used in construction products, including loose-fill attic insulation, acoustic finishes and spray-on fireproofing. Although W.R. Grace marketed their vermiculite insulation products as asbestos-free, the raw ore at the Libby mine contains asbestos – an estimated 21%-26% by weight.

As far back as the 1970s, Grace and its executives knew the ore contained asbestos and hid this vital information from workers and consumers. The result – a town overwhelmed with asbestos disease. (See Pulitzer Prize-winning journalist Andrew Schneider’s latest article on the Libby tragedy here.)

The NIOSH study, in press at Environmental Health Perspectives, has many interesting and important findings, but one that jumped out at me was the 50% increased risk of lung cancer death among workers whose cumulative exposure was less than 4.5 fibers/cc. This finding was just at the edge of statistical significance, and the elevated lung cancer death risk among workers whose cumulative exposure was between 4.5 and 22.9 fibers/cc (still a very low level), was statistically significant.

Since the current OSHA standard is .1 fiber/cc, a lifetime (40 years) of work at the OSHA standard would result in a cumulative exposure history of only 4 fibers/cc. From this study, it looks like 4 fibers/cc is a pretty dangerous exposure. It is one more piece of evidence that there is no safe exposure level, and that asbestos should be banned.

David Michaels heads the Project on Scientific Knowledge and Public Policy (SKAPP) and is Professor and Associate Chairman in the Department of Environmental and Occupational Health, the George Washington University School of Public Health and Health Services.