“These findings add to evidence of a causal association between firefighter and cancer,” said the researchers.

They gathered nearly six decades of data on firefighters from Chicago, Philadelphia and San Francisco, comprising almost 20,000 male firefighters with 1,300 cancer deaths and 2,600 cancer incidence cases.

The results are the second phase of the study. In the first phase, published in October 2013, researchers found that firefighters had higher rates of several types of cancer.

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