I’ve tended not to obsess over chemicals and cancer, because I think there are other risks that are much higher and much more clearly proven (like the high odds of death every time you set foot in or anywhere near a motor vehicle, to give one example.) I also tend to accept some chemicals, like water disinfectants, food preservatives, drugs, even pesticides, as somewhat necessary evils – we actually know they have a downside, but they do more good than harm on balance. In a sense, it is a “luxury” that many of us avoid violence and infectious diseases long enough to get old and die of cancer. Cancer is at least to some extent a random phenomenon. That doesn’t mean we shouldn’t be looking for safer alternatives to these chemicals that do the same good. If we don’t look we won’t find them. And then, there are chemicals that are known to be harmful, and have no positive effects. Triclosan comes to mind. The companies using cynical fear-based marketing to force these on people should be punished.

All that aside, our food, water, air, and consumer products are full of chemicals, with the result that our bodies are full of chemicals. We don’t have good information on what most of them are doing to us, and especially what combinations of them may be doing to us. Here’s an interesting article that estimates what fraction of cancers are caused by chemicals in the environment, as opposed to lifestyle choices, genetics, and plain old bad luck.

Assessing the carcinogenic potential of low-dose exposures to chemical mixtures in the environment: the challenge ahead

Lifestyle factors are responsible for a considerable portion of cancer incidence worldwide, but credible estimates from the World Health Organization and the International Agency for Research on Cancer (IARC) suggest that the fraction of cancers attributable to toxic environmental exposures is between 7% and 19%. To explore the hypothesis that low-dose exposures to mixtures of chemicals in the environment may be combining to contribute to environmental carcinogenesis, we reviewed 11 hallmark phenotypes of cancer, multiple priority target sites for disruption in each area and prototypical chemical disruptors for all targets, this included dose-response characterizations, evidence of low-dose effects and cross-hallmark effects for all targets and chemicals. In total, 85 examples of chemicals were reviewed for actions on key pathways/mechanisms related to carcinogenesis. Only 15% (13/85) were found to have evidence of a dose-response threshold, whereas 59% (50/85) exerted low-dose effects. No dose-response information was found for the remaining 26% (22/85). Our analysis suggests that the cumulative effects of individual (non-carcinogenic) chemicals acting on different pathways, and a variety of related systems, organs, tissues and cells could plausibly conspire to produce carcinogenic synergies. Additional basic research on carcinogenesis and research focused on low-dose effects of chemical mixtures needs to be rigorously pursued before the merits of this hypothesis can be further advanced. However, the structure of the World Health Organization International Programme on Chemical Safety ‘Mode of Action’ framework should be revisited as it has inherent weaknesses that are not fully aligned with our current understanding of cancer biology.