Naturally Occurring Chrysotile (NOC)
Clear Creek contains the largest deposits of naturally occurring chrysotile in North America. NOC is also found in a majority of California counties and all across the United States. This form of asbestos was been mined in Clear Creek for about forty years. The mining companies liked this area because the chrysotile was considered 'pure' or without amphibole contaminates that are found in other NOC deposits. This lack of naturally occurring amphibole asbestos was recently confirmed by Dr. Mark Van Baalen of Harvard University.
While the "asbestos" issue did not surface in a major way until the establishment of the Atlas Superfund site, the Salinas Ramblers were well aware of the issue. The club received a briefing about asbestos risk from Berkeley scientists in the late 1970's and some members participated in the air sampling that was used in the Cooper and Poppendorf study released in 1979. It should be noted that none of the members who participated in this study and who have ridden Clear Creek much of their lives have experienced any asbestos related illness.
Early Quicksilver events in the 1970's and 1980's used roads and trails in what was eventually declared the Atlas Superfund site by the EPA. This was allowed because the entire area was "open" with no restrictions and at the time there was very little BLM oversight of the event or the course. When the superfund site was declared in the late 1980's, we stopped using this area as well as other mine sites.
Contestants were warned about the NOC on the entry form, in the rider information sheet and with a release form that each contestant was required to sign. A dust mask was recommended but very few riders were ever seen wearing a mask. This is confirmed in the 1984 Australian news article about Geoff Ballard.
Starting in the early 1990's the Salinas Ramblers were required as a condition of our use permit to take air samples both during the preparation phase and during the event. Salinas Rambler members wore air samplers while working on the course weeks before the event and contestants were solicited to wear the air sampler during events. To the best of our knowledge, none of the air samples taken during these activities ever exceeded the OSHA threshold for exposure. No event was ever cancelled or postponed by the BLM due to high fiber counts.
Here is documentation from the BLM regarding air sampling from 2004 to 2008.