The concept of environment is often used with a broad
scope in the medical literature, including all nongenetic
factors such as diet, lifestyle and infectious agents. In
this broad sense, the environment is implicated in the
causation of the majority of human cancers (Tomatis
et al., 1990). In a more specific sense, however,
environmental factors include only the (natural or
man-made) agents encountered by humans in their
daily life, upon which they have no or limited personal
control. The most important ‘environmental’ exposures,
defined in this strict sense, include outdoor and
indoor air pollution and soil and drinking water
contamination. Most environmental carcinogens occur
at higher concentrations in the workplace: since the
report of scrotal cancer among chimney sweeps by Pott
(1775), occupational cancer research has played a
pivotal role in the elucidation of environmental causes
of human cancer. Furthermore, control of occupational
exposure circumstances has proven to be feasible and
effective as compared to other cancer preventive
measures.
In the following sections the evidence linking exposure
to selected environmental factors and risk of
cancer will be reviewed, followed by a summary of
current knowledge on occupational carcinogens. Agents
whose exposure depends on lifestyle, such as solar
radiation and food additives, will not be considered, nor
agents occurring in the environment as a consequence of
accidents or warfare