The Particulate Air Pollution Controversy: A Case Study and Lessons Learned
Schlesinger, Richard B., Environmental Health Perspectives
Robert F. Phalen
Boston, MA: Kluwer Academic Publishers, 2002. 144 pp. ISBN: 1-4020-7225-2, $70.00 cloth.
One of the more controversial issues in the field of air pollution concerns public health implications from inhaled ambient particulate matter (PM). This book, organized into 10 chapters, aims to present the various scientific controversies and to examine the field as an overall case study for interfacing science and public policy. Each chapter is independent of the others, and each concludes with a section termed "Lessons Learned," providing a concise summary and overview of the significance of the material presented.
The first half, Chapters 1 through 5, provides a very good overview of concepts and issues involved in PM air pollution: discussions of measuring PM in air; an overview of the epidemiologic evidence, past and current, associating PM with adverse effects on human health and controversies in interpreting these studies; and a discussion of how particles are inhaled into the respiratory tract, how they deposit in the airways, and how they are cleared from the respiratory tract. Phalen's discussion of the evolution of federal PM air pollution regulations in the United States concentrates on regulations issued since 1997 and would have benefited from a broader discussion of how PM regulation has changed from total suspended particulates to P[M.sub.10] to P[M.sub.25] (< 10 to < 2.5 [micro]m) over the years. Finally, the chapter that describes physicochemical properties of particulate matter would have been more useful had it appeared earlier in the book.
The second half of the book, however, digresses from the objectivity of the first half. The discussion of the role that controlled toxicologic studies play in providing a mechanistic basis for the health effects reported by epidemiologic studies is extremely superficial, to the extent that it could be misleading. For example, certain mechanisms of injury are related to what are said to be specific "susceptible" population groups. However, epidemiologic studies are showing that PM can have adverse effects on "normal" individuals as well, depending upon exposure scenarios. In addition, Phalen suggests that particulate inhalation is actually needed to maintain optimal respiratory tract defenses, that there are actually potential health benefits from PM exposure, and that ignoring these will lead to a "distorted picture of the implications to public health." He cites the trend in infectious disease that suggests that avoidance of contact with environmental microbes can reduce immunities. …