ABSTRACT
The first stage in cancer risk assessment is the process known as carcinogenic hazard identification. This is the qualitative determination that a substance, complex mixture, agent, or exposure is capable of causing cancer in humans, that is, it is a carcinogen. An agent is a carcinogen if exposure to it causes an increased incidence of malignant neoplasms at one or more anatomic sites in humans, experimental animals, or both. For suspect agents that are already present in the environment, data that are relevant for carcinogenic hazard identification may be available in the international scientific literature. Carcinogenicity, like most other forms of toxicity, increases in severity with increasing duration and intensity of exposure. However, the relative potencies of various carcinogens are highly variable. Epidemiological Studies to assess the possibly increased risks of cancer in exposed humans are critically reviewed, and the strength of that evidence is evaluated.
