Table 3.

Associations between preterm births and particulate matter concentrations modeled at the 4 km × 4 km resolution by species and sources using chemical transport models in California.

Air pollution indicator	Cases (n)	Controls (n)	IQR	Adjusted OR (95% CI)a	p-Value
UCD/CIT modeled concentrations at the 4 km × 4 km resolution, by fraction and species (years 2000–2008)
Primary PM0.1	395,654	710,316	1.389	1.021 (1.015, 1.028)	< 0.01
OC in PM0.1	395,654	710,316	0.985	1.018 (1.012, 1.024)	< 0.01
EC in PM0.1	395,654	710,316	0.131	1.044 (1.036, 1.052)	< 0.01
SOA in PM0.1	395,654	710,316	0.061	1.130 (1.117, 1.143)	< 0.01
Primary PM2.5	395,654	710,316	8.229	1.036 (1.029, 1.043)	< 0.01
OC in PM2.5	395,655	710,316	3.699	1.020 (1.013, 1.027)	< 0.01
EC in PM2.5	395,654	710,316	1.258	1.040 (1.033, 1.048)	< 0.01
SOA in PM2.5	395,654	710,316	0.239	1.115 (1.102, 1.128)	< 0.01
Ammonium in PM2.5	395,654	710,316	1.188	1.138 (1.126, 1.150)	< 0.01
Nitrates in PM2.5	395,654	710,316	2.914	1.138 (1.128, 1.149)	< 0.01
Sulfates in PM2.5	395,654	710,316	0.535	1.004 (1.000, 1.008)	0.05
UCD_P modeled concentrations at the 4 km × 4 km resolution, by species, in PM2.5 (years 2000–2006)
Potassium	294,860	522,199	0.053	1.013 (1.003, 1.023)	< 0.01
Chromium	294,860	522,199	0.002	0.999 (0.996, 1.001)	0.31
Iron	294,860	522,199	0.190	0.980 (0.967, 0.994)	< 0.01
Titanium	294,860	522,199	0.008	0.992 (0.984, 1.001)	0.09
Magnesium	294,860	522,199	0.004	0.998 (0.990, 1.005)	0.55
Strontium	294,860	522,199	0.001	0.979 (0.969, 0.989)	< 0.01
Arsenic	294,860	522,199	0.001	0.999 (0.997, 1.000)	0.06
Calcium	294,860	522,199	0.048	0.965 (0.955, 0.975)	< 0.01
Zinc	294,860	522,199	0.002	0.982 (0.976, 0.988)	< 0.01
UCD_P modeled concentrations at the 4 km × 4 km resolution, by fraction and sources (years 2000–2006)
Onroad gasoline PM0.1	294,860	522,199	0.083	1.107 (1.091, 1.123)	< 0.01
Onroad diesel PM0.1	294,860	522,199	0.069	1.078 (1.066, 1.091)	< 0.01
Commercial meat cooking PM0.1	294,860	522,199	0.122	1.069 (1.058, 1.081)	< 0.01
Wood burning PM0.1	294,860	522,199	0.272	0.982 (0.975, 0.989)	< 0.01
Onroad gasoline PM2.5	294,860	522,199	0.386	1.091 (1.077, 1.106)	< 0.01
Onroad diesel PM2.5	294,860	522,199	0.397	1.059 (1.049, 1.070)	< 0.01
Commercial meat cooking PM2.5	294,860	522,199	1.084	1.041 (1.033, 1.050)	< 0.01
Wood burning PM2.5	294,860	522,199	1.811	0.985 (0.977, 0.993)	< 0.01
Unit is micrograms per cubic meter. aOdds ratios were estimated using conditional logistic regression models, adjusted for race/ethnicity and educational level using categorical variables and for maternal age and median household income at census block–group level using polynomial functions. Odds ratios are expressed per interquartile range increase in exposure.