Occupational Heat Exposure and Breast Cancer Risk in the MCC-Spain Study.

Background: Mechanisms linking occupational heat exposure with chronic diseases have been proposed. However, evidence on occupational heat exposure and cancer risk is limited. Methods: We evaluated occupational heat exposure and female breast cancer risk in a large Spanish case-control study. We enrolled 1,738 breast cancer cases and 1,910 frequency-matched population controls. A Spanish job exposure matrix, MatEmEsp, was used to assign estimates of the proportion of workers exposed (P greater than or equal to 25% for at least one year) and work time with heat stress (wet bulb globe temperature ISO 7243) for each occupation. We used three exposure indices: ever vs. never exposed, lifetime c…