No dose–no poison

Abstract

Environmental scientists attempt to find a causal connection between pollutants and disease, especially cancer. For most environmental exposures, however, the dose is too low to detect an effect. Only exposure to high doses of chemical substances can be shown to increase the risk for cancer, as is evident by examining the list of definite human carcinogens (IARC group 1). These substances are characterized by a history of very high human exposures, mostly in the workplace (around 50%), but also from chemotherapy/drugs (around 20%) or infections (around 15%). Alcoholism and smoking are two additional examples of cancer being caused by high doses of chemicals. In fact, animal studies have demonstrated that at high enough doses, nearly 50% of tested substances will increase the risk for cancer, including approved drugs and natural pesticides for vegetables [1]. Therefore, it is probable that many more substances would be defined as definite carcinogens if humans were to be exposed to higher doses. Coffee, for example, is an animal carcinogen, and if a large human population drank enough coffee, perhaps 30 cups per day, then it could likely be demonstrated that coffee would increase the risk of bladder cancer in humans as well as animals.