In 2011 this journal published a special issue with an emphasis on the “State of the Science and Mode of Action” as applicable to “Asbestos and Related Mineral Fibers.” Some issues discussed in the papers in that journal issue remain constant regarding asbestos and risks to health. However, for some issues, new data have generated concerns regarding nonasbestos elongated particulates in classical occupational as well as environmental/secondary exposures.
There are several misconceptions that became evident when developing this new special issue. Of note is a misguided assumption that the use of asbestos and asbestos-containing products has been banned in the United States. The U.S. Environmental Protection Agency (EPA) attempted in July 1989 to offer a rule that would have banned asbestos, but the “Asbestos Ban and Phaseout Rule” (40 CFR 763 Subpart 1, Sec. 763.179) was, in large part, vacated and remanded by the U.S. Fifth Circuit Court of Appeals in 1991. There were six asbestos-containing products banned, but these were limited to (1) corrugated paper, (2) rollboard, (3) commercial paper, (4) specialty paper, (5) flooring felt, and (6) new uses of asbestos. The actual utilization of nonbanned asbestos-containing products has been restricted as much by threats of litigation as by federal regulations. The reader is encouraged to review the Federal Register (FR) notices on the EPA Office of Pollution Prevention and Toxics (OPPT) asbestos page under “Laws and Regulations” for more specific comments regarding BANS under the Clean Air Act and The Toxic Substances Control Act.
A major point of confusion remains the use of the term “asbestos.” This term is used in Occupational Safety and Health Administration (OSHA) regulations for the fibrous forms of chrysotile, amosite, crocidolite, actinolite, tremolite, and anthophyllite. On occasion the use of the term “asbestos” is applied more liberally to other fibrous forms of minerals not listed as one of the six regulated entities. Thus, the definition of “asbestos” in the National Emissions Standard for Asbestos (40 CFR 61 Subpart M-61.141 Definitions) is further defined as the “asbestiform varieties of serpentinite (chrysotile), riebeckite (crocidolite), cummingtonite-grunerite, anthophyllite, and actinolite-tremolite.” Asbestiform denotes the “fibrous” growth pattern of the crystals and is a more specific minerology term. However, even papers published recently refer to a mineral fiber as “asbestos” rather than asbestiform when the point of discussion is clearly not one of the six regulated entities.
Another point of concern addressed in the present special issue focuses on the “asbestos” marker disease—mesothelioma. The regulations have revised the permissible exposure limit (PEL) for governed worker populations in an effort to reduce the “heavy-dose” diseases that were common in the past, including asbestosis and other noncarcinogenic pulmonary effects. In fact, the work rules presently in place in the United States are considered by OSHA to still carry a “significant risk for development of cancer.” The counterpoint is that required training, work practices, and the use of personal protection devices reduce exposures below the perceived risk at that PEL.
Nonetheless, mesothelioma is a very rare and unique tumor that has been considered an “asbestos marker disease.” It is also a tumor that can occur in people with lower exposures such as “take-home” bystander or secondary exposures. Compounding the issue further is the fact that the latency for development of mesothelioma is often 30 years or longer from first exposure. There are also occupational or environmental exposures to “nonasbestos” elongated particles that have been linked to mesothelioma. Thus, some of the review papers in this issue present the status of mesothelioma in several countries. Some of these used appreciable asbestos-containing products, while others not only used such products but were a major source of production utilizing one of the unique forms of asbestos. Information is also presented regarding the risk of mesothelioma from exposure to nonasbestos elongated particulates and environmental exposures to these structures.
Finally, it is important to review issues including individual susceptibility and risks from exposure to “asbestos” as well as from nonasbestos elongated mineral particles. Some of the articles include epidemiology observations as well as mechanisms that are involved in induction of elongated mineral particle-related diseases.
In summary, we recognize that not all asbestos-containing products and materials have been banned. Even in the scientific literature there remains confusion surrounding application of the term “asbestos.” Moreover, despite significant reduction of permissible exposure limits of asbestos in regulated work settings and recognition of links between “nonasbestos” elongated mineral fibers and malignancy, mesothelioma remains a marker disease. What are we to conclude from these new data and observations? There is still much to learn about respirable elongated mineral particles and the induction of disease, including risks of exposures to an increasing array of nonasbestos/elongated entities.