Short fiber tremolite free chrysotile mesothelioma cohort revealed

Diagnostic limitations of lung fiber counts in asbestos-related diseases

Background

Lung dust fibre analyses have been used by some pathologists to estimate past asbestos exposure in the workplace and its related health risks. Asbestos, however, especially the predominately applied chrysotile asbestos type, undergoes translocation, clearance and degradation in the lungs.

Objectives

We quantified the asbestos fibre and ferruginous (asbestos) body (FB) content in human tissue with respect to the German asbestos ban in 1993 and the interim period of more than 20 years in order to evaluate the diagnostic evidence of these analyses for asbestos-related diseases (ARD).

Methods

Lung dust analyses have been used in empirical assessments of ARD since 1982. Tissue samples of about 2 cm3 were used and processed in standardized manner. FB was analysed by light microscopy and asbestos fibres by scanning transmission electron microscopy (STEM).

Results

Chrysotile and amphibole fibre concentrations in the lung tissue depend roughly on the cumulative asbestos exposure levels in the workplace.

However, the concentration of lung asbestos fibre and FB depends on the year of examination and especially on the interim period. As the interim period increases, the asbestos fibre burden decreases. There is no relationship between FB and chrysotile asbestos fibre concentrations and only a weak correlation between FB and crocidolite fibre concentrations.

There was no significant difference in chrysotile and amphibole fibre concentrations as well as in FB counts between the different ARD.

Conclusions

Due to the length of interim periods, a past exposure to chrysotile or amphibole asbestos can no longer be detected with FB or asbestos fibre measurement in lung tissue. This means that negative results of such measurements cannot disprove a qualified occupational case history of asbestos exposures and the related health risks due to the fibrogenic and carcinogenic potential of asbestos.

Ongoing downplaying of the carcinogenicity of chrysotile asbestos by vested interests

Industries that mine, manufacture and sell asbestos or asbestos-containing products have a long tradition of promoting the use of asbestos, while placing the burden of economic and health costs on workers and society. This has been successfully done in recent years and decades in spite of the overwhelming evidence that all asbestos types are carcinogenic and cause asbestosis. In doing so, the asbestos industry has undermined the WHO campaign to reach a worldwide ban of asbestos and to eliminate asbestos-related diseases. Even worse, in recent years they succeeded in continuing asbestos mining and consuming in the range of about 1.3 million tons annually. Nowadays, production takes place predominantly in Russia, Kazakhstan and China. Chrysotile is the only asbestos type still sold and represents 95% of asbestos traded over the last century.The asbestos industry, especially its PR agency, the International Chrysotile Association, ICA, financed by asbestos mining companies in Russia, Kazakhstan and Zimbabwe and asbestos industrialists in India and Mexico, continues to be extremely active by using slogans such as chrysotile can be used safely.Another approach of the asbestos industry and of some of its insurance agencies is to broadly defeat liability claims of asbestos victims.In doing so they systematically use inappropriate science produced by their own and/or by industry-affiliated researchers. Some of the latter were also engaged in producing defense material for other industries including the tobacco industry. Frequent examples of distributing such disinformation include questioning or denying established scientific knowledge about adverse health effects of asbestos. False evidence continues to be published in scientific journals and books.The persisting strong influence of vested asbestos-related interests in workers and public health issues including regulations and compensation necessitate ongoing alertness, corrections and appropriate reactions in scientific as well as public media and policy advisory bodies.

Lung injury and expression of p53 and p16 in Wistar rats induced by respirable chrysotile fiber dust from four primary areas of China

Chrysotile products were widely used in daily life, and a large amount of respirable dust was produced in the process of production and application. At present, there was seldom research on the safety of chrysotile fiber dust, and whether its long-term inhalation can lead to lung cancer was unknown. In order to determine whether respirable chrysotile fiber dust of China caused lung cancer, four major chrysotile-producing mine areas in China were selected for this study. Chrysotile fibers were prepared into respirable dust. Particle size was measured by laser particle analysis, morphology was observed by scanning electron microscope, chrysotile fiber phase was analyzed by X-ray diffraction, trace chemical elements were identified by X-ray fluorescence, and the structure and the active groups of the dust were determined after grinding by Fourier transform infrared spectroscopy. Male Wistar rats were exposed to non-exposed intratracheal instillation with different concentrations of chrysotile fiber dust. The rats were weighed after 1, 3, and 6 months, then the lung tissues were separated, the lung morphology was observed, and the pulmonary index was calculated. Pathological changes in lung tissues were observed by optical microscope after the HE staining of tissues, and the gene expression of p53 and p16 was determined by reverse transcription polymerase chain reaction. First, the results showed that the particle sizes of the four fibers were less than 10 μm. Four primary areas of chrysotile had similar fibrous structure, arranged in fascicles, or mixed with thin chunks of material. Second, the elementary composition of the four fibers was mainly chrysotile, and the structure and the active groups of the grinding dust were not damaged. Third, the weights of the treated rats were obviously lower, and the lung weights and the pulmonary index increased significantly (P < 0.05). Fourth, the treated Wistar rat lung tissues revealed different degrees of congestion, edema, inflammatory cell infiltration, and mild fibrosis. Fifth, the p53 and p16 genes decreased in the Mangnai group after 1 month of exposure, and the other groups increased. The expression of p53 and p16 in each group decreased significantly after 6 months (P < 0.05). In conclusion, the respirable chrysotile fiber dust from the four primary areas of China had the risk of causing lung injury, and these changes may be related to the physical and chemical characteristics of chrysotile from different production areas.