Review A Growing Role for Gender Analysis in Air Pollution Epidemiology Jane E. Clougherty Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, USA Objectiv s Ources an D Dat : Epidemiologic studies of air pollution effects on respiratory health report significant modification by sex, although results are not uniform. Importantly, it remains unclear whether modifications are attributable to socially derived gendered exposures, to sex-linked physiological differences, or to some interplay thereof. Gender analysis, which aims to disaggregate social from biological differences between males and females, may help to elucidate these possible sources of effect modification. Dat On : A PubMed literature search was performed in July 2009, extraci using the terms “respiratory” and any of “sex” or “gender” or “men and women” or “boys and girls” and either “PM2.5” (particulate matter ≤ 2.5 µm in aerodynamic diameter) or “NO2” (nitrogen dioxide). I reviewed the identified studies, and others cited therein, to summarize current evidence of effect modification, with attention to authors’ interpretation of observed differences. Owing to broad differences in exposure mixes, outcomes, and analytic techniques, with few studies examining any given combination thereof, meta-analysis was not deemed appropriate at this time. Dat : More studies of adults report stronger effects among women, particularly for older ysnthei persons or where using residential exposure assessment. Studies of children suggest stronger effects among boys in early life and among girls in later childhood. c Onclusi Ons : The qualitative review describes possible sources of difference in air pollution response between women and men, which may vary by life stage, coexposures, hormonal status, or other factors. The sources of observed effect modifications remain unclear, although gender analytic approaches may help to disentangle gender and sex differences in pollution response. A framework for incorporating gender analysis into environmental epidemiology is offered, along with several potentially useful methods from gender analysis. Kye w Or Ds : air pollution, effect modification, epidemiology, gender, sex. Environ Health Perspect 118:167–176 (2010). doi:10.1289/ehp.0900994 available via http://dx.doi.org/ [Online 16 October 2009] There is growing epidemiologic evidence of differing associations between air pollution and respiratory health for females and males. More studies report stronger effects among women and girls than among men and boys, but the literature is far from consistent. Importantly, it is unknown whether observed modification is attributable primarily to biological differ- ences between men and women, to exposure differences (e.g., work-related coexposures), or to some interplay thereof. Gender analysis, which aims to disaggregate social and biologi- cal differences between men and women (e.g., hormonal status), may help to elucidate this modification, identify key mechanisms, and design more effective interventions. The distinction between gender (i.e., self-representation, socially derived activities and roles) and sex (i.e., biological differences by chromosomal complement, including reproductive organs and hormonal composi- tion) (Krieger 2003) speaks to the distinc- tion between exposure and susceptibility. Gender analysis is more common in occupa- tional epidemiology (Arbuckle 2006; Messing and Stellman 2006; Messing et al. 2003; Schachter et al. 2009) than in environmental health (Keitt et al. 2004), because persistent job stratification by sex (Alexanderson and Östlin 2001) has produced marked differ- ences in occupational exposures to chemi- cal agents (Hursidic-Radulovic et al. 2002; London et al. 2002), ergonomic demands (Silverstein et al. 1986), injury (Salminen et al. 1992), and psychosocial stressors (Arcand et al. 2000; Bourbonnais et al. 2000; Gutek 2001; Hall 1989). Gender, a social construct, includes cul- tural norms, roles, and behaviors shaped by relations among women and men and among girls and boys (Krieger 2003). Gender, inher- ently social, varies continuously over multiple dimensions over the life course, whereas sex is normally dichotomous. Gender is shaped at the societal level and varies across nation, cul- ture, class, race, ethnicity, nationality, sexual- ity, and religion. Gender describes patterns of behavior, place, and role, determining where people spend time and their activities, thereby shaping exposure distributions. Sex, a biological construct, is based on physiologic differences enabling reproduc- tion, defined by physiologic characteristics (especially reproductive organs) or chro- mosomal complement (Krieger 2003). Sex- linked traits (e.g., hormonal status, body size) influence biological transport of environmen- tally derived chemicals. Lung size and growth, deposition of fine particles [particulate matter ≤ 2.5 µm in aerodynamic diameter (PM2.5)] (Kim and Hu 1998, 2006), gas absorption (Jones and Lam 2006), gas–blood barrier per- meability (Brauner et al. 2009), airway hyper- responsiveness (Kanner et al. 1994), vascular Environmental Health Perspectives • volume 118 | number 2 | February 2010 response (Prisby et al. 2008), and inflamma- tion (Hermes et al. 2006; Sood et al. 2008) all differ, on average, by sex. Sex and gender can be difficult to distin- guish in epidemiologic data; they are tightly intertwined, with reciprocal effects. Biological characteristics (e.g., body size) become engen- dered as occupational and family roles, which are gendered expressions of biology. Likewise, gendered work and caregiving roles, smoking, and alcohol consumption influence muscle mass, adiposity, and chemical body burden— collectively, these are socially derived biologi- cal expressions of gender (Krieger 2003). In this review I present a framework for incorporating gender analysis into air pollution epidemiology, describing pathways through which gender and sex, separately and multi- plicatively, may influence pollution response. Current evidence of effect modification in air pollution respiratory epidemiology is summa- rized, and potentially useful nascent analytic methods from gender analysis are offered. Gender analysis explores topics far beyond those addressed here, including sexuality and transgender issues. Here I consider only those constructs and tools that may directly inform mean differences between men and women in air pollution epidemiology. A Framework for Incorporating Gender Analysis into Environmental Epidemiology Incorporating aspects of gender analysis into the environmental health paradigm (Figure 1) actualizes this distinction between gender and sex. The framework is elucidated by draw- ing examples broadly from environmental epidemiology, elucidating pathways through which gender and sex may, individually and recursively, shape population exposure and susceptibility. Concentration to exposure. Gender shapes where people spend time and activ- ity patterns—for example, sports participa- tion, work-related chemical and ergonomic Address correspondence to J.E. Clougherty, Harvard School of Public Health, Department of Environmental Health, Landmark Building, 4th Floor West, 401 Park Dr., Boston, MA 02215 USA. Telephone: (617) 816-7717. Fax: (202) 442-2642. E-mail: jcloughe@hsph.harvard.edu Many thanks to N. Krieger, M. Perry, J. Dennerlein, J. Levy, and C. Katz for helpful suggestions in the early development of the manuscript and to N. Jeffrey and M. Simons for reviewing the manuscript. The author declares she has no competing financial interests. Received 17 May 2009; accepted 16 October 2009. 167