title: Methods for assessing the extent of exposure and effects of air pollution.
abstract: OBJECTIVE
  In many places in Europe, the ambient air pollution exceeds the levels considered to be safe for health. The objective of the paper is to review and summarise the methods of assessment of its impact on health, and to indicate the contributions of various research disciplines, particularly environmental epidemiology.
  
  
  METHODS
  The framework for assessment of impact is based on a four stage model: assessment of release of pollutant; assessment of exposure; assessment of the consequence; and risk estimation.
  
  
  RESULTS
  Epidemiology is crucial in providing the data for the assessment of consequence. The criteria that determine the use of epidemiological studies for this task include lack of bias, correct control of confounding, and measured estimates of exposure. At present, those criteria are easier to satisfy for studies of short term effects on health than for the delayed consequences of exposure, or exposure accumulated over a prolonged period. Combinations of results from various populations through meta-analysis of existing studies or conducting multicentre studies is often necessary to increase the reliability of the consequence assessment stage.
  
  
  CONCLUSIONS
  To assess the impact on health systematically helps to focus on actions to limit air pollutants with the greatest impacts on human health and on the most affected populations. This method allows identification of the most pertinent questions which have to be answered by studies on relations between pollution and health and on exposure of populations to air pollutants. Epidemiology has considerable potential to contribute to this research.
authors.affiliation: WHO European Centre for Environment and Health, Bilthoven, De Bilt, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Krzyzanowski
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D000397:Air Pollution / Q000009:adverse effects / Q000032:analysis; D015982:Bias; D015986:Confounding Factors, Epidemiologic; D003625:Data Collection / Q000379:methods*; D004781:Environmental Exposure / Q000032:analysis*; D006801:Humans; D018570:Risk Assessment
chemical_list: D000393:Air Pollutants