Asbestos is a known human carcinogen with no known safe levels of exposure. Other, non-regulated minerals are also hazardous and behave similarly to asbestos when inhaled. In particular, Erionite is a carcinogenic mineral, but is non-regulated.
The risk for adverse health effects increases with increasing exposure over time because the amphibole fibers remain in the body. This is particularly worrisome for children, as early life exposures have more time to manifest in disease (latency period).
In Libby, Mont., and other sites in the U.S., and other nations, there is significantly increased risk for disease in areas where people are being exposed to sources of asbestos in the environment.
For example, researchers at the University of California, Davis, found increased risk of malignant mesothelioma with residential proximity to naturally occurring asbestos. That information was published in an American Journal of Respiratory and Critical Care Medicine article: Residential Proximity to Naturally Occurring Asbestos and Mesothelioma Risk in California
Recently, Dr. Francine Baumann from the University of Hawaii with co-authors from UNLV, Bloomsberg University, and the USDA/NRCS published the study, "The presence of asbestos in the natural environment is likely related to mesothelioma in young individuals and women from Southern Nevada." This study hypothesizes that mesothelioma caused by environmental exposure to asbestos might be initially distinguishable from that caused by occupational exposure by looking at male-to-female ratios in younger people (< 55 yrs old). The hypothesis is that environmental exposure should occur at earlier ages than occupational (even since birth), therefore mesothelioma will occur in younger individuals (< 55 yrs old). Environmental exposures should also occur equally to both men and women, therefore male to female ratios in those < 55 yrs old is important to examine. In contrast, occupational exposure occurs at older ages, therefore mesothelioma tends to occur later in life (> 55 yrs old), and occurs primarily in men (male to female ratios that vary from 4:1 to 6:1) because it is usually men that do jobs where asbestos exposure occurs. Of course actually determining causes of mesothelioma must be done in a case-by-case basis. This paper uses the above hypothesis to indicate where environmentally-exposed mesothelioma might be occurring so that researchers can focus additional research in those locations.
This paper was published in the Journal of Thoracic Oncology and was singled out as “Editor’s Choice”:
“Baumann and colleagues present interesting data with public health implications in terms of environmental asbestos exposure and the development of mesothelioma in young women in Nevada, USA. The manuscript — The presence of asbestos in the natural environment is likely related to mesothelioma in young individuals and women from Southern Nevada Baumann et al - will undoubtedly generate debate in the public health community and is worthy of significant attention.” — quote from Editor.
The USEPA recently released an inhalation reference concentration (RfC) value for chronic exposure for non-cancer health effect.
The RfC is defined as an estimate of exposure that is likely to be without an appreciable risk of adverse health effects over a lifetime (70 yrs). The RfC is expressed in terms of the lifetime exposure in units of fibers per cubic centimeter of air (fibers/cc) as measured by phase contrast microscopy (PCM). The chronic RfC value for non-cancer health effects is 0.00009 f/cc.
Results for ambient air are presented in the Final Phase I Site Characterization Report for the Boulder City Bypass Naturally occurring Asbestos (NOA) Project Phase I (Railroad Pass to Silverline Road).
Ambient air was measured in the area of Railroad Pass, for Phase I of the Boulder City Bypass (see final report). Reported values from May 8 to August 10, 2014 vary from non-detect to 0.0014 s/cc with an average of 0.00021 s/cc.
Hazard Quotient HQ = Ambient air concentration/Reference concentration. Using the limited data available (3 months summer 2014): HQ = 0.0002/0.00009 = 2.33. If the Hazard Quotient is calculated to be less than 1, then no adverse health effects are expected as a result of exposure.
Note that OSHA (Occupational Safety and Health Administration) has a Permissible Exposure Limit (PEL) for asbestos that is 0.1 f/cc as an 8 hr time-weighted average. As you can see this number is much higher than the 0.00009 f/cc listed above. OSHA admits that although these levels are permissible, they do involve significantly increased health risk. In addition, the OSHA PEL only counts the 6 regulated asbestos minerals, therefore the asbestos minerals that are similar to those in Libby Montana that are found in and around Wilson Ridge in Arizona, and erionite, do not count towards the permissible exposure limit.
Exposure to asbestos is known to cause the following diseases: