Clougherty and girls than among men and boys. Two- day lagged coefficient of haze (COH) expo- sures predicted increased risks among women. For girls 0–14 years of age, 1- to 2-day lagged NO2, sulfur dioxide (SO2), and carbon mon- oxide (CO) exposures predicted elevated risks. Among males, only 1-day lagged PM10 predicted increased risks among adults. The authors proposed sex-differing biological explanations (e.g., hormonally affected inflam- mation, smooth muscle and vascular function, lung growth and decline, airway and paren- chymal size), citing evidence of sex-differing airway PM2.5 deposition (Kim and Hu 1998; Kohlhaufl et al. 1999) and greater responsivity Study 1997 2005 Luginaah et al. Studies reporting stronger effects among girls Brunekreef et al. 877 Dutch children (7–12 years of age) in 1995 883 children (0–14 years of age) in Windsor, Ontario, Canada 1995–2000 Oftedal et al. 2008 2,307 9- and 10-year-old IQR increase in lifetime Change in PEF children in Oslo, Norway NO2, PM2.5, PM10 Oosterlee et al. 291 Haarlem, Netherlands, Living on heavy (vs. light) children (0–15 years of age) trafficked streets to tobacco smoke among females (Chen et al. 1999, 2005; Gold et al. 1996; Hursidic- Radulovic et al. 2002; Prescott et al. 1997; Varkev 2004; Xu et al. 1994a, 1994b). They considered gendered explanations; women are, on average, poorer and may experience greater (or different) psychosocial stressors, perform more household tasks (increasing exposures to viral infection, indoor allergens, combustion exhaust, cleaning solvent, and aeroallergens) (Redline and Gold 1994), and may differ from men in health-care seeking and illness manage- ment behaviors (Goodman et al. 1994). One Chicago cohort studied by Ito and Thurston (1996) showed greater all-cause and respiratory mortality with same- and previous- day PM10 among black women than among other sex/race groups. The authors observed that physiologic differences and gender differ- ences in activities, occupation, and class may shape pollution response, noting that race and gender were yet unexplored in environmental epidemiology. In the Public Health and Air Pollution in Asia (PAPA) study, Kan et al. (2008) reported stronger associations between pollut- ants [PM10 (PM with aerodynamic diameter < 10 µm) SO2, NO2, ozone (O3)] and daily respiratory mortality among women, elderly, and lower socioeconomic status (SES) persons. Table 2. Studies examining effect modification by sex among children. Population Exposure metric(s) Outcome(s) of interest Risk among males Risk among females Truck traffic density (for children within 300 m of motorway) IQR increase in 1-, 2-, 3-day lag NO2, SO2, CO, COH, O3, PM10, TRS Residential outdoor NO2, presence of gas stove Lifetime ambient NO2, PM2.5, and O3 PM10, NO2 Residential traffic Distance to busy road Modeled NO2 community of freeway IQR increase in 4-day personal PM2.5 Outdoor residential exposure gradient 1.5 µg/m3 in PM2.5, 0.4 × 10–5/m abs, 8.5 µg/m3 NO2 Residence in high- vs. low-pollution area IQR difference in community lifetime ambient acid, NO2, PM2.5, O3 IQR increase in mean O3, Change in FEV1 High- vs. low-exposure Percent difference Change in FVC FEV1 RR of respiratory hospitalization FEF25 FEF50 Wheeze (ever) Wheeze (1-year) Dyspnea (ever) Dyspnea (1-year) RR of wheezing bronchitis FVC FEV1 PEFR MMEF Percent difference in FEV1 FEF25–75 in FVC FEV1.0 Chronic cough Wheeze FEV1 Cough without infection Dry cough at night Slower growth in FVC FEV1 Prevalence of wheeze β = –1.1 (–6.7 to 4.9) β = –1.8 (–7.5 to 4.2) RR(lag1 SO2) = 0.95 (0.87 to 1.04) RR(lag2 CO) = 0.996 (0.93 to 1.06) RR(lag2 CO) = 0.997 (0.87 to 1.14) RR(lag1 NO2) = 0.93 (0.81 to 1.07) β (NO2) = –69.1 mL/sec (–135.3 to –3.0) β (PM10) = –57.9 mL/sec (–116.2 to 0.4) β (PM2.5) = –30.1 mL/sec (–79.7 to 19.5) OR = 1.2 (0.4–3.7) OR = 0.7 (0.2–2.5) OR = 0.9 (0.2–3.2) OR = 0.4 (0.1–2.6) RR (NO2 > 0.7) = 0.7 (0.4–1.3); p-trend = 0.10 RR (gas stove) = 0.9 (0.5–1.8) β (NO2) = –29.9 L/min (SE = 29.5) β (PM2.5) = 8.3 L/min (SE = 24.5) β (03) = 52.0 L/min (SE = 65.8) β (PM2.5) = 32.0 L/min (SE = 30.1) β (O3) = –4 mL (–10 to 2) β (PM10) = –15 mL (–23 to –6) β (NO2) = –25 mL (–33 to –18) β = –4% (–29 to 21) β = –26% (–81 to 29) β = 1.45% (p < 0.05) β = 1.41% (p < 0.01) OR = 1.05 (0.50–2.22) OR = 1.29 (0.45–3.68) β = –16% (–26 to –6) OR (PM2.5) = 1.43 (1.14–1.80) OR (abs) = 1.38 (1.11–1.71) OR (NO2) = 1.52 (1.16–2.00) OR (PM2.5) = 1.39 (1.08–1.78) OR (abs) = 1.31 (1.04–1.67) OR (NO2) = 1.45 (1.07–1.98) OR (FVC) = 2.15 (1.25–3.69) OR (FEV1) = 1.90 (1.12–3.25) OR (NO2) = 1.47 (1.04–2.09) OR (acid) = 1.55 (1.03–2.32) β = –6.3 (–11.4 to –0.8) β = –6.2 (–11.5 to –0.6) RR(lag1 SO2) = 1.11 (1.01 to 1.22) RR(lag2 CO) = 1.07 (1.00 to 1.14) RR(lag2 CO) = 1.19 (1.02 to 1.38) RR(lag1 NO2) = 1.19 (1.002 to 1.41) β (NO2) = –94.5 mL/sec (–166.6 to –22.4) β (PM10) = –77.9 mL/sec (–141.9 to –14.0) β (PM2.5) = –68.9 mL/sec (–120.8 to –16.9) OR = 4.4 (1.4–13.6) OR = 5.3 (1.1–25.0) OR = 4.8 (1.3–17.7) OR = 15.8 (1.4–174.4) RR (NO2 > 70) = 2.7 (1.1–6.8); p-trend= 0.02 RR (gas stove) = 2.4 (1.0–5.9) β (NO2) = –63.8 (SE = 18.3) β (PM2.5) = –47.6 (SE = 14.4) β (03) = –250.9 (SE = 69.9) β (PM2.5) = –130.0 (SE = 30.3) β (O3) = –12 mL (–18 to –6) β (PM10) = –11 mL (–20 to –3) β (NO2) = –30 mL (–37 to –22) β = –23% (–49 to 2); p for difference = 0.25 β = –103% (–163 to –43); p for difference = 0.06 β = 2.52% (p < 0.001) β = 2.03% (p < 0.001) OR = 2.45 (1.16–5.16) OR = 3.05 (1.11–8.41) β = –1% (–16 to 14) OR (PM2.5) = 1.19 (0.84–1.70) OR (abs) = 1.25 (0.87–1.78) OR (NO2) = 1.22 (0.81–1.85) OR (PM2.5) = 1.17 (0.81–1.68) OR (abs) = 1.16 (0.79–1.71) OR (NO2) = 1.20 (0.78–1.84) OR (FVC) = 1.50 (0.84–2.68) OR (FEV1) = 1.39 (0.78–2.44) OR (NO2) = 0.85 (0.59–1.21) OR (acid) = 1.08 (0.71–1.66) Continued, next page 1996 1995 Pershagen et al. Peters et al. 1999 Rojas-Martinez et al. 2007 Rosenlund et al. 2009 Stern et al. 1989 197 children (4 months to 4 years) hospitalized with wheeze, 350 controls 3,293 children in 12 Southern California communities 3,170 children (8 years of age) in Mexico City, 1996–1999 2,107 children 9–14 years of age in 40 Rome schools 1,630 children (7–12 years of age) in rural Canada Van Vliet et al. 1,498 children in 13 schools Residence within 100 m 1997 Studies reporting stronger effects among boys Delfino et al. 2004 14 boys and 5 girls with Gehring et al. 2002 1,756 German infants asthma, 9–17 years of age Jedrychowski et al. 1,001 children in Krakow, (1999) Poland Peters et al. 1999 3,676 children in 12 Southern California communities 170 ovlume 118 | number 2 | February 2010 • Environmental Health Perspectives