Smoking can Increase the Number of Asbestos Fibers in Airways

Asbestos workers that were smokers have an increased incidence of disease.  Another interesting study on point is called, "Cigarette smoke increases the penetration of asbestos fibers into airway walls." By D. McFadden, J. Wright, B. Wiggs, and A. Churg - Am J Pathol. 1986 April; 123(1): 95–99.   Here is an excerpt: "Abstract - For study of the penetration of asbestos fibers into airway walls, guinea pigs were given amosite asbestos by intratracheal instillation. Half of the animals were also exposed to cigarette smoke. Animals were sacrificed at 1 week and 1 month, and numbers of fibers in airway walls were counted in histologic sections. In both smoke-exposed and nonexposed groups, numbers of fibers per square millimeter of airway wall increased from 1 week to 1 month in the respiratory bronchioles. At each time period, smoke-exposed animals had significantly higher numbers of fibers in the airway walls, compared with nonexposed animals. It is concluded that 1) continued transport of fibers into interstitial tissues may be the reason that asbestosis can progress after cessation of exposure; 2) cigarette smoke increases the penetration of fibers into airway walls. This effect may play a role in the increased incidence of disease seen in smoking, compared with nonsmoking, asbestos workers."

Another interesting study is called, "Gastrointestinal cancer mortality of workers in occupations with high asbestos exposures" by Seong-Kyu Kang, MD, PhD, Carol A. Burnett, MS, Eugene Freund, MD, James Walker, PhD, Nina Lalich, MSPH, John Sestito, JD, MS - American Journal of Industrial Medicine - Volume 31 Issue 6, Pages 713 – 718.  Here is an excerpt: "Abstract - Asbestos, which is a well-known risk factor for lung cancer and malignant mesothelioma, has also been suggested as a gastrointestinal (GI) carcinogen. This study was conducted to assess the relationship between high asbestos exposure occupations and the occurrence of GI cancer. Death certificate data were analyzed from 4,943,566 decedents with information on occupation and industry from 28 states from 1979 through 1990. Elevated proportionate mortality ratios (PMRs) for mesothelioma were used to identify occupations potentially having many workers exposed to asbestos. All PMRs were age-adjusted and sex- and race-specific. The PMRs for GI cancers in white males were then calculated for these occupations after excluding mesothelioma, lung cancer, and non-malignant respiratory disease from all deaths. We identified 15,524 cases of GI cancer in the 12 occupations with elevated PMRs for mesothelioma.

When these occupations were combined, the PMRs for esophageal, gastric, and colorectal cancer were significantly elevated at 108 (95% confidence interval = 107-110), 110 (106-113), and 109 (107-110), respectively. Esophageal cancer was elevated in sheet metal workers and mechanical workers. Gastric cancer was elevated in supervisors in production and managers. Colorectal cancer was elevated in mechanical and electrical and electronic engineers. However, high exposure occupations like insulation, construction painter supervisors, plumbers, furnace operators, and construction electricians showed no elevations of GI cancers. In conclusion, this death certificate study supports an association between asbestos exposure and some GI cancer, however the magnitude of this effect is very small. Am. J. Ind. Med. 31:713-718, 1997.

A third study is called, "Pleural carcinogenic potency of mineral fibers (asbestos, attapulgite) and their cytotoxicity on cultured cells." By Jaurand MC, Fleury J, Monchaux G, Nebut M, Bignon J. - J Natl Cancer Inst. 1987 Oct;79(4):797-804.  Here is an excerpt: "Abstract - The carcinogenicity of several samples of mineral fibers was tested following injection of 20 mg in the pleural cavity of noninbred Sprague-Dawley rats. Three samples of chrysotile asbestos (mean length: 3.2, 2.1, and 1.2 micron) induced mesotheliomas at a rate of 48, 52, and 19%, respectively. The first sample was acid leached prior to intrapleural injection; in that group, the percentage of mesotheliomas was reduced to 25%. Treatment with amosite and crocidolite resulted in the occurrence of 57 and 56% of mesotheliomas. Acid-treatment of amphiboles did not significantly modify the percentage of mesotheliomas. When the Stanton's fiber dimensions were taken into consideration to correlate with mesothelioma incidence, the observed number of mesotheliomas in the chrysotile-treated animals was much lower than that expected, suggesting that other fiber parameters (chemistry, physicochemistry) play a role in the carcinogenicity. Attapulgite fibers (mean length: 0.77 micron) did not induce tumor, and the mean survival time was of the same order as that observed in the control groups. The injection of quartz resulted in no mesothelioma but did result in 6 malignant histiocytic lymphomas (17%) and 2 malignant schwannomas (6%). In vitro experiments did not show strong correlation between cytotoxicity and the carcinogenic potency of these minerals, but the qualitative cellular responses might give some indications on the fiber's potency. In addition, the in vitro effects of the fibers seem to be modulated by their size."

If you found any of these excerpts, please read them in their entirety.  We all owe a debt of gratitude to these researchers.