Asbestos Exposure Threshold
No scientist has been able to find a threshold under which asbestos exposure does not pose a risk for developing cancer. This means there is no safe level of asbestos exposure.
Historically, industrial hygienists established threshold limit values (TLVs) to limit the amount of asbestos to which workers were exposed. TLVs were intended to limit the risk of developing asbestosis. They were not intended to protect workers from cancer.
We now know that the TLVs were not even effective to prevent asbestosis. Experience has shown that even people who did not work with or around asbestos have developed asbestosis because they lived near a mine, for example. A recent study showed elevated incidence of asbestosis among people living within 10 miles of the Belvidere Mountain asbestos mine in northern Vermont. And hundreds of residents of Libby, Montana have developed the disease, whether or not they worked in W.R. Grace’s nearby asbestos-contaminated vermiculite mine.
In any event, the evidence from asbestos cases has repeatedly shown that workers were regularly exposed to asbestos at levels well above the TLV. Asbestos fibers are so small that an individual could be exposed to a significant level of asbestos without being able to see, feel, taste or smell any evidence of it. If dust levels in the work environment were high enough that dust from asbestos products was visible, the level of exposure was very high. According to asbestos experts, if dust from asbestos products was visible, the asbestos exposure was over the TLV.