Several studies report a lower than expected mortality in lung cancer among workers exposed to organic dust. Here are two recent ones with the same remarkable outcome:

Lung and other cancer site mortality in a cohort of Italian cotton mill workers
G Mastrangelo, E Fadda, R Rylander, G Milan, U Fedeli, M Rossi di Schio, J H Lange
Occupational and Environmental Medicine 2008;65:697-700 (free abstract)

Evaluation of the mortality from lung and other cancer sites in a cohort of 3961 Italian cotton mill workers, divided into those working with carding (exposed to high levels of endotoxin-containing cotton dust) and other tasks, which generally have lower exposure. Standardised mortality ratios (SMRs), with 95% confidence intervals (CI), were calculated using death rates of the regional general population as a reference. Cancer mortality was analysed in relation to the length of employment in the two task groups.

Among workers in carding departments, lung cancer SMRs were 1.88 (CI: 0.69 to 4.08) for <6 yrs of employment, 1.01 (CI: 0.20 to 2.94) for  6-12 yrs of employment and 0.22 (CI: 0.00 to 1.24) for >12 years of employment. A significant (p = 0.04) trend was confirmed by Poisson regression. No reduced risks were found for other forms of cancer, nor for those working with other tasks. The results support the conclusion that a high and prolonged exposure to cotton dust and other endotoxin-containing organic dusts is related to a lower risk of lung cancer. There was no indication of a reduced risk for other forms of cancer.

Lung cancer risk among textile workers in Lithuania
Irena Kuzmickiene and Mecys Stukonis, Institute of Oncology, Vilnius University, Lithuania
Journal of Occupational Medicine and Toxicology 2007 (open access)

The purpose of this study was to investigate risk of lung cancer incidence in textile industry workers by the type of job and evaluate the relation between occupational textile dusts exposure and lung cancer risk in a cohort. Altogether 14650 textile workers were included in this retrospective study and were followed from 1978 to 2002. Lung cancer risk was analyzed using the standardized incidence ratios (SIR) calculated by the person-years method. 

The lung cancer risk for male in the cotton textile production unit was significantly lower after 10 years of employment (SIR = 0.34; 95% CI 0.12-0.73). The lung cancer risk decreased with level of exposure to textile dust (p for trends was <0.05): the SIR for the low, medium, high and very high level of cumulative exposure were 1.91 (95% CI 0.92-3.51), 1.30 (95% CI 0.52-2.69), 0.77 (95% CI 0.21-1.96), and 0.24 (95% CI 0.03-0.86) respectively. High level of exposure to cotton dusts appears to be associated with a reduced risk of lung cancer in cotton textile workers.

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