This investigation reviews the epidemiological evidence of reduced cancer rates in workers exposed to dusty environments. The reported reduced rates are most prevalent for lung cancer. The suggested mechanism for reduced rates is stimulation of the immune system by endotoxin, which is the major contaminant of many dusts, including cotton. Epidemiological investigations in cotton, wood and agricultural industries have shown lower than expected death rates from cancer. The cellulose manufacturing industry have shown equal to expected lung cancer death rates. A review of smoking patterns of these groups do not explain reduced cancer rates. This evidence suggests some dusty occupations including cotton and wood may have beneficial anti-cancer effects.