Environmental Pollution in Urban Environments and Human Biology
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7 Aug 2003 8:27 AR AR196-AN32-06.tex AR196-AN32-06.sgm LaTeX2e(2002/01/18) P1: IKH 10.1146/annurev.anthro.32.061002.093218 Annu. Rev. Anthropol. 2003. 32:111–34 doi: 10.1146/annurev.anthro.32.061002.093218 Copyright c 2003 by Annual Reviews. All rights reserved First published online as a Review in Advance on June 4, 2003 ENVIRONMENTAL POLLUTION IN URBAN ENVIRONMENTS AND HUMAN BIOLOGY Lawrence M. Schell and Melinda Denham Department of Anthropology, University at Albany, State University of New York, 1400 Washington Ave., Albany, New York, 12222; email: [email protected], [email protected] Key Words growth, lead, noise, stress, urbanism ■ Abstract The biocultural approach of anthropologists is well suited to understand the interrelationship of urbanism and human biology. Urbanism is a social construction that has continuously changed and presented novel adaptive challenges to its residents. Urban living today involves several biological challenges, of which one is pollution. Using three different types of pollutants as examples, air pollution, lead, and noise, the impact of pollution on human biology (mortality, morbidity, reproduction, and develop- ment) can be seen. Chronic exposure to low levels of these pollutants has a small impact on the individual, but so many people are exposed to pollution that the effect species- wide is substantial. Also, disproportionate pollutant exposure by socioeconomically disadvantaged groups exacerbates risk of poor health and well being. URBANISM AND HUMAN BIOLOGY Urban growth began slowly several thousand years ago and has accelerated tremen- dously over the past 300 years. By 2006, half of the world’s population will be living in urban places (United Nations 1998). If current trends continue, the char- acteristic environment of the human species will be urban. The change from nonurban to urban living has occurred over too few genera- tions to provide much opportunity for evolutionary adaptation to urban challenges. Homo sapiens evolved in response to the physical and social demands of a hunting and gathering way of life and death during the Paleolithic and before. Many of these demands are absent from the urban environment today, and new challenges are present in abundance including altered energy budgets from urban activity pat- terns and diets, psychosocial stress, steep social gradients, increased contact be- tween social groups resulting in increased transmission and evolution of infectious disease, and increased pollution largely from transportation and industry (Schell & Ulijaszek 1999). Given the novelty of so many urban challenges and the antiquity of our response systems, a reasonable question is, “Are we suited for urban living?” As urban forms are social products, understanding urbanism and human biol- ogy involves the study of a complex biocultural interaction. An anthropological 0084-6570/03/1021-0111$14.00 111 7 Aug 2003 8:27 AR AR196-AN32-06.tex AR196-AN32-06.sgm LaTeX2e(2002/01/18) P1: IKH 112 SCHELL DENHAM approach that integrates sociocultural variables and biological measures of adap- tation and health is well suited to the problem. However, understanding effects of industrial pollution on humans requires study designs that differ from those employed to study small-scale societies. Studies of the effects of urbanism on human health have used two basic designs: studying urban populations and studying people exposed to features of urban environments wherever they may occur. The former approach is exemplified in the urban rural comparison. Urban rural comparisons suffer from the usual flaws inherent in reducing multidimensional differences into a simple dichotomy, each of which exists as a continuum. Today we know that urban rural differences in health vary depending on the particulars of each of the urban and rural places compared. Replication of results, a hallmark of science, is impossible when the identities being compared change. Indeed, urban rural differences may not be apparent even though substantial differences in the factors that influence health exist because these factors, some positive and some negative, may sum to zero. The most obvious urban rural differences, such as those that existed during the height of unregulated industrialization, are now reduced to varying degrees in different countries. Nevertheless, some urban features continue to be highly detrimental to health and well-being. The second approach, studying urban features, is preferred because it involves the analysis and measurement of individual factors representing dimensions of urbanism (e.g., population size or density, stress levels, activity patterns, specific pollutants). It also involves measuring covariates that if unmeasured, as in urban rural contrasts, may confound the attribution of true causes. This measurement- based approach is more likely to lead to replication and generalization. It is the stronger approach also because in many societies exposure to pollution covaries with socioeconomic disadvantage (Schell & Czerwinski 1998), a known influ- ence on human health. Measuring both the putative causes and the covarying factors is a necessary step in determining the true influence of urbanism on human biology. The epistemology of urban research is similar to that in epidemiology. Ex- perimental research in which the investigator can randomize exposures is rare or nonexistent, and observational research designs without the investigator’s in- tervention are common. Observational designs produce evidence that is evalu- ated in terms of Hill’s postulates in which proper temporal order of cause and effect, the presence of dose-response relationships, replication, and biological plausibility figure largely (Lilienfeld & Stolley 1994). A special type of obser- vational research design is the natural experiment in which experimental con- ditions are altered by chance. This approximates randomization but does not involve the investigator’s intervention in human circumstances. Sample bias is far less likely to influence results compared to studies without randomization. This review emphasizes results from studies employing measurement-based approaches that meet the epistemological standards of population-based research. 7 Aug 2003 8:27 AR AR196-AN32-06.tex AR196-AN32-06.sgm LaTeX2e(2002/01/18) P1: IKH URBAN POLLUTION AND HUMAN BIOLOGY 113 AIR POLLUTION The air we breathe is polluted with the byproducts of combustion from indus- try, power generation, and transportation, as well as the manufacture and use of chemicals. Air pollutants are a heterogeneous group of gases and particles that can remain airborne for long periods of time. Common air pollutants are oxides of nitrogen (NOx), oxides of sulfur (SOx), ozone (O3), carbon monox- ide (CO), and particulate matter (PM). In sufficient concentrations, these gases and particles can harm human health in the short (burning of eyes and throat, difficulty breathing) and the long term (cancer and long-term damage to the immune, neurological, reproductive, and respiratory systems) (Waldbott 1978). Air pollution is especially problematic in urban areas. In 1999, of the six com- mon pollutants used by the EPA to monitor national air quality, levels of CO, NO2,SO2, and PM10 were higher in urban areas (U.S. Environ. Prot. Agency 2001). Mortality (All Cause) Air pollution is a significant risk factor for all-age, all-cause mortality in urban areas (Brunekreef & Holgate 2002, Schwela 2000). Ozone, CO, SOx, and PM have each been associated with increased mortality rates (Abbey et al. 1999, Borja-Aburto et al. 1998, Fairley 1999, Lee et al. 1999, Neas et al. 1999, Pope et al. 2002, Xu et al. 2000, Zmirou et al. 1998). Exposure to specific air pollutants has been associated with increased cause-specific mortality rates, especially cardiovascular and respiratory disease deaths (Fairley 1999, Xu et al. 2000, Zmirou et al. 1998). Brunekreef (1997) has estimated that chronic, low-level exposure to air pollution shortens life expectancy by one to two years, a substantial effect compared to other environmental risk factors. For biological anthropologists, pre-reproductive mortality is especially impor- tant because it focuses on the evolutionary impact of air pollution. Fewer studies have considered air pollution and mortality solely in children. Most of these stud- ies have found positive relationships between pollutants and sub-adult mortality (Bobak & Leon 1999, Loomis et al. 1999, Pereira et al. 1998, Woodruff et al. 1997) in varied populations (Mexico, Brazil, Czech Republic, United States) and at different developmental stages (prenatal, neonatal, infant). Several studies have reported significant associations with mortality even when air pollution levels did not exceed national or World Health Organization stan- dards (Fairley 1999, Lee et al. 1999, Schwartz 1991). For example, Schwartz (1991) demonstrated a dose-response relationship between total suspended par- ticulates (TSP) and daily mortality in Detroit when levels were less than half of the U.S. standard. Recent research suggests that through the mediating ef- fect of socioeconomic factors, air pollution may have a greater impact on mor- tality in disadvantaged groups (Abbey et al. 1999, Brunekreef 1999, Pope et al. 2002). 7 Aug 2003 8:27 AR AR196-AN32-06.tex AR196-AN32-06.sgm LaTeX2e(2002/01/18) P1: IKH 114 SCHELL DENHAM Morbidity Although air pollution can have health effects throughout the body, the target organ for many major urban air pollutants is the respiratory system. In a recent review, Schwela