Occupational exposures and colorectal cancers: A quantitative overview of epidemiological evidence.

A traditional belief widespread across the biomedical
community was that dietary habits and genetic predisposition
were the basic factors causing colorectal
cancer. In more recent times, however, a growing evidence
has shown that other determinants can be very
important in increasing (or reducing) incidence of this
malignancy. The hypothesis that environmental and
occupational risk factors are associated with colorectal
cancer is gaining ground, and high risks of colorectal
cancer have been reported among workers in some
industrial branches. The aim of this study was to investigate
the epidemiologic relationship between colorectal
cancer and occupational exposures to several industrial
activities, by means of a scientific literature review and
meta-analysis. This work pointed out increased risks
of colorectal cancer for labourers occupied in industries
with a wide use of chemical compounds, such as
leather (RR = 1.70, 95%CI: 1.24-2.34), basic metals (RR
= 1.32, 95%CI: 1.07-1.65), plastic and rubber manufacturing
(RR = 1.30, 95%CI: 0.98-1.71 and RR = 1.27,
95%CI: 0.92-1.76, respectively), besides workers in the
sector of repair and installation of machinery exposed
to asbestos (RR = 1.40, 95%CI: 1.07-1.84). Based on
our results, the estimated crude excess risk fraction attributable
to occupational exposure ranged from about
11% to about 15%. However, homogeneous pattern
of association between colorectal cancer and industrial
branches did not emerge from this review.