Polypropylene production and colorectal cancer: a review of the epidemiological evidence.

Polypropylene has been produced for over 35 years and has a wide variety of applications including industrial uses, food packaging and many domestic uses. As a high-molecular-weight polymer, polypropylene is considered chemically inert with little or no physiological or toxicological effects. Nevertheless, early epidemiological studies of polypropylene production workers and carpet manufacturing employees who use polypropylene reported a significant excess of colorectal cancer. In one study, five of the seven cases were diagnosed within a five-month period, and in the other study, five cases were diagnosed within an 18-month period. Recent updates of these two study populations have found no continuation of the excess of colorectal cancer, thereby indicating that the earlier observations on these two groups reflected the chance nature of a time-space cluster. Moreover, investigations of polypropylene production workers in the United States, Germany, Australia and the United Kingdom found no association with colorectal cancer. When the results of all studies of polypropylene production workers are pooled, the summary risk ratio for colorectal cancer is 1.37 (95% confidence interval 0.83-2.11). Taken together, the epidemiological evidence and the absence of toxicological data do not support a causal association between polypropylene and colorectal cancer.