Cancer Case Control Studies And Asbestos Exposure Of General Population

People that have worked within the asbestos industry or where the mineral was used in that products they handled are generally at higher risk for developing cancer and mesothelioma. One interesting study that examines the advantage of bleach digestions is called,  A procedure for the isolation of amosite asbestos and ferruginous bodies from lung tissue and sputum  by Marion G. Williams Jr. a; Ronald F. Dodson b; Carolyn Corn a;George A. Hurst .

Here is an excerpt:  A comprehensive scheme is described for isolating amosite asbestos and ferruginous bodies from fixed and unfixed human lung tissue and sputum. This qualitative procedure avoids many of the problems associated with previous isolation techniques and illustrates the advantages of brief bleach digestions. The samples are digested in prefiltered Wright laundry bleach (9.2% sodium hypochlorite), collected on 0.2-m Nuclepore filters by vacuum filtration, rinsed with distilled water and absolute ethanol, and examined visually for excessive residue. If organic residues are suspected or are known to occur, the sample is treated sequentially with 2% potassium permanganate, 8% oxalic acid, and 9.2% sodium hypochlorite, and rinsed with distilled water and absolute ethanol.

The ethanol, potassium permanganate, and oxalic acid steps can be repeated as often as needed until the desired sample volume has been filtered. The entire procedure allows large volumes to be filtered and yields filters that have extremely clean backgrounds. Filtration can be completed in as little as 15 min, as opposed to the hours or days recommended for other procedures. The technique is applicable to specimens fixed in Saccomanno’s fixative or giutaraldehyde, and to those in an unfixed state. The procedure does not appear to damage the gross morphology of the amosite fibers, and it does not produce a detectable change in their elemental composition when determined by energy-dispersive X-ray analysis.+

The second interesting study is called, Incidence of cancer and mortality among employees in the asbestos cement industry in Denmark.  By E Raffn, E Lynge, K Juel, B Korsgaard – Br J Ind Med 1989;46:90-96   Here is an excerpt:  Abstract – In a cohort study of the incidence of cancer and mortality among 7996 men and 584 women employed in the Danish asbestos cement industry between 1928 and 1984 over 99% were traced.

The only fiber type that was used until 1946 is chrysotile asbestos. While amosite and crocidolite were also introduced during that time. Asbestos is used 89% crysotile constituted, 10% amosite and 1% crociodite. The exposure levels were high during the first 25 years of manufacture, especially in areas where asbestos was used in dry condition. Measurements from 1948 indicate that the fibre levels may have ranged from 100 to 1600 times over the present Danish threshold limit value of 0.5 fibre/ml.

More than 41% personal sample were higher than 2 f/ml in 1973. Within 5 years of starting employment, about 76% of the workforce left the factory. Between 1943 and 1984 there are 612 cases and 1346 death because of cancer were observed in cohort.

Among employed men the overall mortality (O/E 1.18; 95% CI 1.12-1.25), cancer mortality (O/E 1.32; 95% CI 1.19-1.46), and overall incidence of cancer (O/E 1.22; 95% CI 1.12-1.32) were significantly increased compared with all Danish men.This was not so among employed women. For men, significant excess risks were found for cancer of the lung (O/E 1.80; 95% CI 1.54-2.10), pleura (O/E 5.46; 95% CI 2.62-10.05), mediastinum (O/E 5.00; 95% CI 1.01-14.61), stomach (O/E 1.43; 95% CI 1.03-1.93), and other male genital organs (O/E 3.03; 95% CI 1.11-6.60). The mortality was significantly increased for men for non-malignant pulmonary diseases (O/E 1.63; 95% CI 1.33-1.98). Among the group of asbestos cement workers with first employment 1928-40 an excess risk of laryngeal cancer was found (O/E 5.50;95% CI 1.77-12.82). A total of 12 cases of pleural and one of peritoneal mesotheliomas was observed when the original notification forms were reviewed for all patients with cancer in the cohort.

A third study entitled,  Asbestos-related pleural plaques and lung cancer by Weiss W. – Department of Medicine, Hahnemann University, Philadelphia. – Chest. 1994 Aug;106(2):648-9. Here is an excerpt: – The English-language literature was reviewed to evaluate a possible relationship between asbestos-related pleural plaques and lung cancer in the absence of parenchymal asbestosis. There were six cohort studies in which the comparison group was limited to unexposed persons or the general population, four lung cancer case-control studies, and three autopsy studies. Of the 13 investigations, only 3 supported the hypothesis that lung cancer risk is elevated among persons with pleural plaques over the risk in unexposed people: 2 cohort studies from the same city in England with much the same data and 1 case-control study. These three studies had the most defects in design. The other ten studies failed to confirm the hypothesis. Thus, the weight of the evidence favors the conclusion that persons with asbestos-related pleural plaques do not have an increased risk of lung cancer in the absence of parenchymal asbestosis.

Read the entire study if you found this study interesting and helpful.

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