Exposures to environmental pollution remain a major source of health risk
throughout the world, though risks are generally higher in developing
countries, where poverty, lack of investment in modern technology and weak
environmental legislation combine to cause high pollution levels. Associations
between environmental pollution and health outcome are, however, complex
and often poorly characterized. Levels of exposure, for example, are often
uncertain or unknown as a result of the lack of detailed monitoring and
inevitable variations within any population group. Exposures may occur
via a range of pathways and exposure processes. Individual pollutants may be
implicated in a wide range of health effects, whereas few diseases are directly
attributable to single pollutants. Long latency times, the effects of cumulative
exposures, and multiple exposures to different pollutants which might act
synergistically all create difficulties in unravelling associations between
environmental pollution and health. Nevertheless, in recent years, several
attempts have been made to assess the global burden of disease as a result of
environmental pollution, either in terms of mortality or disability-adjusted life
years (DALYs). About 8–9% of the total disease burden may be attributed to
pollution, but considerably more in developing countries. Unsafe water, poor
sanitation and poor hygiene are seen to be the major sources of exposure,
along with indoor air pollution.