Cancer mortality in Iowa farmers, 1971-78.

Age-adjusted cancer mortality rates from 1971 to 1978 for male farmers and nonfarmers were computed from Iowa death certificate information. Only data for white males were included in the study because of the limited number of nonwhite farmers in Iowa and because of incomplete occupational information available on females. Mortalities from major types of cancer for farmers and nonfarmers were compared by means of proportionate mortality ratios (PMR). The combined mortality rate for all types of cancer was significantly lower for farmers (PMR = 0.97), due primarily to the significantly lower rates for smoking-related cancers: lung, PMR = 0.78; esophagus, PMR = 0.74; mouth other than lip, PMR = 0.82; and other respiratory cancers, PMR = 0.65. However, the mortality rates for the following cancers were significantly higher for farmers: lip, PMR = 1.62; stomach, PMR = 1.14; leukemia, PMR = 1.10; lymphatic, PMR = 1.14; multiple myeloma, PMR = 1.27; and prostate, PMR = 1.10. Each of the six types of cancer with a significantly elevated mortality in Iowa farmers has also been reported as having an elevated mortality in farmers in other states.