Asbestos-Related Research : First Objectivity then Conclusions

Asbestos-related risks have been extrapolated from the past, when high-dose occupational exposures were frequent. The linear no-threshold dose-response pattern has been assumed, but its applicability to low-dose asbestos exposures has never been proven. Morphologically, malignant mesothelioma can resemble various cancers. There are diagnostic algorithms; however, a tumor diagnosed by standard methods as mesothelioma is not a welldefined entity, in all cases substantially different from other cancers. Well-aimed search and screening effect have probably contributed to the enhanced incidence of mesothelioma and other asbestosrelated diseases in exposed populations. Asbestos-related diseases have been extensively studied in Russia. The prevailing view is that, if all precautions are observed, modern technologies of asbestos production and processing are acceptably safe, whereas bans and prohibitions applied by some countries are excessive. At the same time, there are economic interests to promote chrysotile. Biases due to industrial interests have compromised the objectivity of some asbestosrelated reports. In the author’s opinion, the “all fibers equal” basis of official regulations can be accepted provisionally pending objective and reliable evidence on toxicity of different asbestos types and manmade substitutes. On the basis of independent scientific data, the bans and restrictions on asbestos in some countries should be re-examined and potentially revised. Any permit of continued production or use of asbestos materials must be coupled with regulations and efficient measures to prevent environmental contamination associated even with minimal additional risks. Asbestos-related risks have been estimated on the basis of extrapolations from the past, when high-dose occupational and non-occupational exposures were frequent. Evolution of the concept of lowvs. high-dose asbestos exposures can be illustrated by the gradual decline of the Permissible Exposure Limit (PEL) adopted by the Occupational Safety and Health Administration (OSHA): 197112 f/cc of air as a 8 h time weighed average; 19725; 1976-2; in 1986, the current PEL for asbestos in the workplace was established: 0.1 f/ cc [1,2]. A well-known asbestos contamination was the “Mr Fluffy” incident in Australia (1960-70s), where loose asbestos was used for insulation of houses [3]. In Russia, corrugated asbestos board has been broadly used for roofing being often sawed by hand; asbestoscement pipes are routinely used for drinking water distribution (Figure 1) [4]. Other asbestos-containing materials (flat sheets, asbestos paper, cloth, gaskets, etc.) are broadly used now as before. The linear no-threshold dose-response pattern has generally been assumed for the low exposure levels, but its applicability to low-dose asbestos exposures has never been proven. In some places, asbestos fibers are present in the natural environment due to erosion of surface deposits. For example, the fibers were detected in the lungs of 63.6% deceased individuals from the general population [5]. Inhalation and discharge of the fibers occur normally [6], probably within a dynamic equilibrium. Existence of a threshold for the exposure to mineral fibers has not been reported, but may be assumed by analogy with other environmental factors that have induced evolutionary adaptation [7,8]. Further research into non-linear, threshold cancer risk models is warranted both for asbestos [9], and for its substitutes. Apparently, the screening effect has contributed to the enhanced registered incidence of asbestos-related diseases in exposed populations and an over estimation of the dose-response relationship. In particular, mesothelioma (Mt) was sought among exposed people and correspondingly more often found. Malignant Mt is an uncommon neoplasm developed by a small percentage of people exposed to asbestos. It can be spontaneous, or occur when asbestos fibers are present in the pulmonary or pleural tissues. Apart from asbestos, other potential etiologic factors of malignant Mt are mineral (erionite) and artificial (ceramic, carbone nanotubes) fibers [10-13], virus SV40, radiation, and genetic predisposition [14-17] (Figure 2). Misclassification of disease is a problem for several of the cancer Sergei V. Jargin* Department of Pathology, People’s Friendship University of Russia, Russia *Address for Correspondence Sergei V. Jargin, Department of Pathology, People’s Friendship University of Russia, Clementovski per 6-82, 115184 Moscow, Russia, Tel: +7 495 9516788; E-mail: sjargin@mail.ru Submission: 12 October, 2015 Accepted: 01 December, 2015 Published: 07 December, 2015 Copyright: © 2015 Jargin SV. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Review Article Open Access