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Re: The Occupational Hygiene Hypothesis

Dear Editor

The hygiene hypothesis has grown into a popular idea for explaining the increase in asthma and atopy in children,[1,2] although it remains controversial.[3]

This hypothesis can be extended to adults, especially those in certain occupations. It is suggested that there is another form of the hygiene hypothesis – called the occupational hygiene hypothesis.[4] In 1965, it was observed that those exposed to textile (cotton) dust exhibited a lower than expected rate of lung cancer.[5] This concept was elucidated in a sentinel paper [6] published in 1985; the authors’ suggested that the agent responsible for reduced lung cancer rates was endotoxin (lipopolysaccharide), a cell wall component of gram negative bacteria. Since that time, these initial findings were confirmed by several epidemiological studies in cotton textile workers, reviewed in a recent meta-analysis,[7] and by observation in other occupations[8,9] that are exposed to endotoxin. Finally, an experimental study supported these epidemiological findings.[10] It is also suggested that such occurrences exist for other exposures and occupations, but have yet to be described.[11] This suggests that this is a new area of science that has not been explored, except by a few.

With the discovery of Toll-like receptors,[12] mechanisms of endotoxin have been better clarified and explaining how immune stimulation can result in reduced rates of lung cancer.

Sadly, this letter is dedicated to my mentor (JHL), Professor Jan L. Sykora, who died on June 25, 2003. He provided me with the wisdom to explore a murine model [13] for establishing evidence of the “occupational hygiene hypothesis”.

References

(1) Weiss ST. Eat dirt-the hygiene hypothesis and allergic diseases. N Engl J Med 2002;347:930-1.

(2) Braback L. Does farming provide protection from asthma and allergies? Acta Paediatr 2002; 91: 1147-54.

(3) Liu AH, Murphy JR. Hygiene hypothesis: fact or fiction? J Allergy Clin Immunol 2003; 111: 471-8.

(4) Lange JH, Rylander R, Fedeli U, Mastrangelo G. Extension of the "hygiene hypothesis" to the association of occupational endotoxin exposure with lower lung cancer risk. J Allergy Clin Immunol 2003; 112: 219-220

(5) Enterline PE. Mortality among asbestos products workers’ in the United States. NY Acad Sci 1965; 132: 156-65.

(6) Enterline PE, Sykora JL, Keleti G, Lange JH. Endotoxin, cotton dust and cancer. Lancet 1985; 2:934-5.

(7) Mastrangelo G, Fedeli U, Fadda E, Milan G, Lange JH. Epidemiologic evidence of cancer risk in textile industry workers: a review and update. Tox Ind Health; in press.

(8) Mastrangelo G, Marzia V, Marcer G. 1996. Reduced lung cancer mortality in diary farmers: is endotoxin exposure the key factor? Am J Ind Med 30:601-609.

(9) Mastrangelo G, Marzia V, Milan G, Fadda E, Fedeli U, Lange JH. 2003a. An exposure-dependent reduction of lung cancer in dairy farmers. Indoor and Built Environment;in press.

(10) Lange JH. Anti-cancer properties if inhaled cotton dust: a pilot experimental investigation. J Environ Sci Health 1992;27A:505-514

(11) Lange JH. Reduced cancer rates in agricultural workers: a benefit of environmental and occupational endotoxin exposure. Med Hypotheses 2000; 55: 383-5.

(12) Dabbagh K, Lewis DB. Toll-like receptors and T-helper-1/T-helper- 2 responses. Curr Opin Infect Dis 2003;16:199-204

(13) Lange JH, Sykora JL. Evaluation of the anti-cancer properties of aerosolized endotoxin from Enterobacter agglomerans. In The Proceedings 12th Cotton Dust Research Conference Beltwide Cotton Research Conferencs, New Orleans, LA January 6-7, 1988, Jacobs RR and Wakelyn PJ, Eds. Memphis: National Cotton Council, 139-140.