Introduction and recommendations: working group on indoor air and other complex mixtures.

Air in indoor and outdoor environments typically contains many gaseous and particulate pollutants that may affect adversely any individual at sufficiently high concentrations and more sensitive individuals at lower concentrations. The public health relevance of addressing the effects of mixtures is becoming increasingly evident as we improve the concept of total personal exposure to pollution and obtain more data from personal monitoring. The papers within this volume represent the deliberations of a working group assembled with the goal of improving the epidemiologic approach to investigating the health effects of indoor air pollution and other complex mixtures. The group, composed of epidemiologists, human and animal toxicologists, and experts on biomarkers, comprehensively reviewed the methodologic issues involved in investigating complex mixtures. Members noted the deficiencies of current epidemiologic methodology for studying complex mixtures and called for broad-based advances in study design, exposure assessment, outcome assessment, and data analysis and interpretation. Understanding the health effects of complex mixtures will require multidisciplinary research using not only epidemiologic studies incorporating the new methods of exposure assessment but animal and clinical toxicology.