H3K4me2 H3K9ac Mean OD Mean OD Variable n (95% CI) p-Valuea (95% CI) Age (years) < 39 22 0.90 (0.79–1.02) 0.41 (0.22–0.59) 39–47 20 1.00 (0.96–1.05) 0.43 (0.26–0.59) > 47 21 0.94 (0.88–1.00) 0.47 0.43 (0.27–0.58) BMI (kg/m2) < 25 21 0.96 (0.9–1.02) 0.48 (0.33–0.62) 25–27.5 21 0.89 (0.78–1.01) 0.20 (0.04–0.35) > 27.5 21 0.99 (0.95–1.03) 0.57 0.59 (0.45–0.74) Smoking Nonsmoker 24 0.96 (0.88–1.04) 0.44 (0.28–0.61) Former smoker 14 0.87 (0.76–0.97) 0.35 (0.12–0.59) Current smoker 25 0.98 (0.92–1.05) 0.14b 0.43 (0.30–0.57) No. of cigarettes/day 0 38 0.93 (0.87–0.99) 0.41 (0.28–0.54) 1–10 10 0.98 (0.92–1.05) 0.39 (0.23–0.55) > 10 15 0.98 (0.87–1.09) 0.29 0.46 (0.24–0.68) Smoking duration (years) 0 23 0.97 (0.88–1.05) 0.45 (0.28–0.62) 0–19 19 0.90 (0.8–1.00) 0.35 (0.15–0.54) > 19 21 0.97 (0.91–1.03) 0.94 0.45 (0.32–0.58) Pack-years 0 24 0.96 (0.88–1.04) 0.44 (0.28–0.61) 0–4 17 0.92 (0.84–0.99) 0.39 (0.22–0.57) > 4 20 0.95 (0.86–1.04) 0.79 0.43 (0.25–0.61) ap-Value test for trend. bp-Value, one-way analysis of variance. p-Valuea Variable H3K4me2 n Mean OD (95% CI) p-Valuea 0.88 0.36 0.76b 0.69 0.98 0.90 Education Primary school 12 0.96 (0.83–1.09) Middle school 37 0.94 (0.89–0.99) High school 14 0.96 (0.81–1.10) Area of residence City center 8 0.89 (0.54–1.23) Suburbs 41 0.97 (0.92–1.01) Rural 12 0.91 (0.79–1.03) Self-reported traffic intensity near home High 5 0.86 (0.43–1.29) Medium 38 0.94 (0.89–1.00) Low 18 0.97 (0.91–1.03) Granulocyte (%) 45–55 21 0.95 (0.88–1.01) 55–61 21 0.94 (0.82–1.06) 61–76 21 0.96 (0.91–1.02) Years of employment < 9 20 0.88 (0.75–1.00) 9–21 17 0.96 (0.91–1.02) > 21 22 0.99 (0.95–1.04) 0.98 0.94 0.26 0.76 0.04 Metal-rich air particles and histone modifications et al. 2009). In particular, nickel and arsenic, which were most consistently associated with increased H3K4me2 in our analyses, were also previously found to increase H3K4me2 in vitro (Zhou X et al. 2009). In our study, we found that H3K4me2 was correlated with the lev- els of exposure to nickel, arsenic, and iron, but only nickel and arsenic showed significant associations with H3K4me2 when we evalu- ated cumulative exposures. Also, we found sig- nificant associations of cumulative exposures to nickel and arsenic with increased H3K9ac. Table 3. Association of the subjects’ characteristics with H3K4me2 and H3K9ac (in OD units) measured on the fourth day of a work week. Table 4. Association of personal level of exposure to PM metal components and total PM mass with H3K4me2 and H3K9ac. Association with H3K4me2 Unadjusted Adjusteda Association with H3K9ac Unadjusted Adjusteda β-Coefficient (95% CI) p-Value β-Coefficient (95% CI) p-Value β-Coefficient (95% CI) p-Value β-Coefficient (95% CI) Exposure Aluminium Manganese Nickel Zinc Arsenic Lead Iron PM10 PM1 Exposure Aluminium Manganese Nickel Zinc Arsenic Lead Iron PM10 PM1 0.01 (–0.02 to 0.04) 0.02 (–0.01 to 0.04) 0.15 (0.03 to 0.28) 0.05 (–0.01 to 0.11) 0.16 (0.03 to 0.28) 0.02 (–0.01 to 0.04) 0.12 (0.01 to 0.24) 0.03 (–0.03 to 0.09) 0.02 (–0.06 to 0.1) Unadjusted 0.01 (–0.03 to 0.04) 0.01 (–0.02 to 0.04) 0.11 (–0.01 to 0.23) 0.06 (–0.03 to 0.15) 0.14 (0.03 to 0.26) 0.02 (–0.02 to 0.06) 0.09 (–0.03 to 0.21) 0.03 (–0.04 to 0.11) 0.03 (–0.07 to 0.13) 0.36 0.21 0.02 0.08 0.02 0.19 0.04 0.34 0.64 0.61 0.33 0.07 0.21 0.01 0.35 0.14 0.41 0.53 0.02 (–0.01 to 0.05) 0.02 (–0.01 to 0.05) 0.16 (0.03 to 0.3) 0.05 (–0.01 to 0.12) 0.16 (0.02 to 0.3) 0.02 (–0.01 to 0.05) 0.14 (0.01 to 0.26) 0.04 (–0.03 to 0.11) 0.03 (–0.06 to 0.13) Adjustedb 0.02 (–0.02 to 0.06) 0.02 (–0.02 to 0.05) 0.16 (0.01 to 0.3) 0.06 (–0.05 to 0.17) 0.16 (0.03 to 0.29) 0.02 (–0.03 to 0.06) 0.12 (–0.02 to 0.27) 0.05 (–0.04 to 0.14) 0.07 (–0.06 to 0.21) 0.24 0.17 0.02 0.12 0.02 0.16 0.03 0.23 0.45 0.44 0.35 0.03 0.30 0.02 0.38 0.09 0.26 0.29 –0.04 (–0.11 to 0.02) –0.03 (–0.08 to 0.02) 0.22 (–0.04 to 0.48) –0.05 (–0.18 to 0.07) 0.18 (–0.08 to 0.45) –0.04 (–0.09 to 0.02) 0.21 (–0.02 to 0.45) –0.08 (–0.2 to 0.04) –0.04 (–0.2 to 0.13) Unadjusted –0.02 (–0.09 to 0.04) –0.01 (–0.07 to 0.04) 0.26 (0.04 to 0.49) –0.02 (–0.21 to 0.16) 0.30 (0.09 to 0.51) –0.03 (–0.11 to 0.05) 0.25 (0.03 to 0.48) 0.00 (–0.14 to 0.15) 0.08 (–0.11 to 0.28) 0.15 0.25 0.10 0.41 0.17 0.16 0.08 0.17 0.65 0.48 0.63 0.02 0.80 0.01 0.42 0.03 0.99 0.40 Data are regression coefficient (β) and 95% CI expressing the change in histone modifications (OD units) associated with an increase in exposure equal to the difference between the 90th and 10th percentile of the exposure distribution. aMultivariable regression models adjusted for age, BMI, education, pack-years, and percent granulocytes. Table 5. Association of cumulative level of exposurea to PM metal components and total PM mass with H3K4me2 and H3K9ac. Association with H3K4me2 Association with H3K9ac β-Coefficient (95% CI) p-Value β-Coefficient (95% CI) p-Value β-Coefficient (95% CI) p-Value β-Coefficient (95% CI) p-Value Data are regression coefficient (β) and 95% CI expressing the change in histone modifications (OD units) associated with an increase in exposure equal to the difference between the 90th and 10th percentile of the exposure distribution. aCumulative levels of exposure were estimated as the product of personal level of exposure to PM metal components or total PM mass and years of employment in the job. bMultivari- able regression models adjusted for age, BMI, education, pack-years, and percent granulocytes. Environmental Health Perspectives • volume 119 | number 7 | July 2011 H3K9ac Mean OD (95% CI) 0.25 (0.05–0.45) 0.43 (0.31–0.56) 0.55 (0.36–0.74) 0.30 (0.05–0.64) 0.49 (0.38–0.60) 0.26 (0.02–0.50) 0.39 (0.15–0.92) 0.46 (0.33–0.58) 0.36 (0.18–0.53) 0.43 (0.3–0.57) 0.42 (0.19–0.65) 0.41 (0.28–0.54) 0.22 (0.04–0.39) 0.43 (0.28–0.58) 0.51 (0.37–0.66) –0.03 (–0.1 to 0.03) –0.01 (–0.06 to 0.04) 0.24 (–0.02 to 0.51) –0.06 (–0.19 to 0.07) 0.21 (–0.06 to 0.48) –0.02 (–0.08 to 0.04) 0.22 (–0.03 to 0.47) –0.04 (–0.17 to 0.09) 0.00 (–0.18 to 0.18) Adjustedb –0.03 (–0.1 to 0.05) 0.00 (–0.06 to 0.05) 0.27 (0.01 to 0.54) –0.03 (–0.24 to 0.18) 0.28 (0.04 to 0.51) –0.02 (–0.1 to 0.06) 0.24 (–0.03 to 0.5) 0.00 (–0.17 to 0.17) 0.08 (–0.17 to 0.32) p-Valuea 0.04 0.43 0.57 0.86 0.006 p-Value 0.33 0.73 0.07 0.38 0.13 0.52 0.08 0.51 0.97 0.48 0.86 0.04 0.78 0.02 0.65 0.08 0.97 0.54 967