Preface

It is an often quoted and highly significant statistic that in the developed world the average person spends about 90% of their time indoors. Despite this, almost all of our knowledge of the effects of ambient air pollution derives from outdoor measurements and air quality management policy is focused upon monitoring and controlling levels of pollution outdoors. Slowly, however, things are changing and the scientific study of pollution of the indoor environment is increasing, although there still have been very few studies of the effects of indoor pollutant exposures on health. In the less developed world, such exposures can be extreme when they arise from unvented combustion appliances used in the home. However, the focus of this volume is upon the developed world.

Indoor air pollution arises both from indoor emissions and from the infiltration of outdoor air. The first two chapters by Ioar Rivas and co-authors and Otto Hänninen and Patrick Goodman look, respectively, at the indoor and outdoor sources that affect the quality of air in the indoor environment. There are many human activities that lead to pollution of the indoor environment and, among other things, the first chapter looks closely at the school as an indoor environment that is likely to experience high pollution levels. The way in which outdoor air pollutants enter the indoor environment is considered in depth in the second chapter. The third chapter, by Tuan Vu and Roy Harrison, considers the chemical and physical properties of pollutants in the indoor environment. Factors such as the size distribution of particulate pollutants and their volatility determine their lifetime in the indoor environment, in addition to influencing the dose to the lung when the indoor air is inhaled.

For pollutants that have major indoor sources but are relatively scarce in the outdoor environment, passage from indoors to outdoors can be a significant source of pollutants in the outdoor environment. In the fourth chapter, Stuart Harrad uses halogenated chemicals, such as polychlorinated biphenyls and brominated flame retardants, as a case study of indoor emissions as a source of outdoor pollution. Chemical reactions in the indoor atmosphere can also be important, both as a source of newly formed pollutants and as a cleansing mechanism for some toxic molecules. It has recently been realized that the fragrances used in many domestic products, designed to produce a pleasant smell in the indoor atmosphere, can be oxidized to form particles of potentially high toxicity. This and other indoor chemical processes are reviewed by Nicola Carslaw in the fifth chapter. Many of the reactions important in the outdoor atmosphere are also found to affect indoor air.

Up to this point, this volume has considered indoor pollution as primarily a chemical phenomenon. However, it should not be forgotten that the indoor atmosphere contains many biological particles, and this topic is addressed in the sixth chapter by Ian Colbeck and Corinne Whitby. Modern methods of molecular biology are facilitating the characterization of organisms in the indoor atmosphere; these can arise from a range of human activities, including poor building maintenance, and some can present a significant threat to health, particularly through their allergenic properties. In the seventh chapter, Juana Maria Delgado-Saborit takes a comparative look at indoor and outdoor air as contributors overall to air pollution exposure; this serves to highlight the importance of the indoor atmosphere as an exposure medium. Such exposures can lead to adverse effects on health, and in the final chapter Robert Maynard gives a succinct overview of this vast area of research and highlights some of the adverse impacts of pollutant exposure occurring in the indoor environment.

We are delighted to have attracted this group of leading researchers to provide authoritative overviews of specific topic areas and we believe that overall the volume represents a comprehensive evaluation of many of the scientific characteristics and implications of indoor air pollution. This volume will prove valuable to scientists, students, consultants and policymakers seeking definitive insights into the topic of indoor air pollution.

Ronald E. Hester

Roy M. Harrison