Yes, it's asbestos.

Federal mineralogists have now corroborated what toxicologists from another agency reported last year: Sierra-foothills communities around Sacramento, Calif., are built atop soils naturally laced with asbestos.

The confirmatory findings appear in a December 2006 report by Gregory P. Meeker and his team at the U.S. Geological Survey (USGS) in Denver.

Last spring, a San Francisco-based Environmental Protection Agency team demonstrated that everyday activities, such as bike riding, gardening, and baseball, could churn up high concentrations of asbestos-laden dust from soils in the foothills area (SN: 7/8/06, p. 26). In response, a construction-materials trade group brought in a consulting firm. The consultants concluded that the minerals EPA had measured didn't qualify as asbestos, weren't toxic, and shouldn't be subject to regulation. EPA responded by commissioning Meeker's team to address the consultants' assertions.

The USGS scientists employed various technologies to study the mineral fibers. They report that although the naturally occurring fibers that they collected in El Dorado Hills, Calif., "do not meet the [structural] definitions of commercial-grade asbestos" these fibers do qualify chemically and in other ways as asbestos--and are potentially toxic.