Naturally Occurring Asbestos

Naturally occurring asbestos has been identified in many states, often in rocks called serpentinite and in certain other mineral formations. Parts of California are well known for serpentine rock, which is the state rock and can contain chrysotile. Areas of Nevada near Las Vegas have also been studied for naturally occurring asbestos. Deposits exist in parts of the East Coast and other regions as well. Geological surveys and state agencies publish maps showing where these formations are likely. Not every rock in these areas contains asbestos, and testing is needed to confirm it.

Exposure usually happens when the ground is disturbed. Construction grading, quarrying, road building and landscaping can release fibers. Gravel from serpentine rock has sometimes been used on unpaved roads and playgrounds, where traffic and wind raise dust. Hikers, off-road riders and residents of affected areas may encounter some exposure. Generally, the levels involved are lower than those seen in heavy occupational settings, but risk increases with frequent, dusty activities. Workers who dig or grade in affected areas can have higher exposure than residents. Dust control measures can reduce these exposures considerably.

California's air quality rules require dust control measures for construction, grading and quarrying in areas likely to contain naturally occurring asbestos. Measures can include watering, covering materials, limiting vehicle speeds and monitoring air. Other states and local agencies have their own guidance. If you work in construction or quarrying in these areas, your employer should follow these rules and provide training. Residents can reduce dust at home by avoiding disturbing bare soil in affected areas and by using wet cleaning methods rather than dry sweeping. Following local guidance helps keep household dust levels low.

1. 1

   Check your state geological survey maps if you live or work in a known serpentine area.

2. 2

   Ask employers about dust control plans on grading or quarry jobs in affected regions.

3. 3

   Use wet methods rather than dry sweeping to clean dust in affected areas.

4. 4

   Record any long-term residence or work in regions known for naturally occurring asbestos.