If you're referring to the study blaming colon cancer on processed meats, it's a major reach.

It was an epidemiological study, which are notorious for poor controlling of variables. If the effect has a relative risk increase greater than 100% (i.e. doubles risk or more), then you can use the results of an epidemiologal study, but results less than that should be treated with a lot of skepticism. This particular study was only 18%, well within the error bounds of this type of study.

For contrast, the epidemiological studies used to establish a causal link between smoking and lung cancer had a risk increase in the ballpark of 10,000%