Table 2.
Associations between preterm births and measured air pollutant concentrations interpolated by empirical Bayesian kriging in California.
| Air pollution indicator | Cases (n) | Controls (n) | IQR | Adjusted OR (95% CI)a | p-Value |
|---|---|---|---|---|---|
| Single pollutant models (years 2000–2008) | |||||
| Total PM2.5 | 422,431 | 808,038 | 6.45 | 1.133 (1.118, 1.148) | < 0.01 |
| O3 | 424,203 | 815,150 | 11.53 | 1.096 (1.085, 1.108) | < 0.01 |
| NO2 | 421,936 | 806,224 | 9.99 | 1.079 (1.065, 1.093) | < 0.01 |
| Two-pollutant model including both total PM2.5 and O3 (years 2000–2008) | |||||
| Total PM2.5 | 421,068 | 802,401 | 6.45 | 1.120 (1.106, 1.134) | < 0.01 |
| O3 | 11.53 | 1.100 (1.088, 1.112) | < 0.01 | ||
| Two-pollutant model including both total PM2.5 and NO2 (years 2000–2008) | |||||
| Total PM2.5 | 418,654 | 792,894 | 6.45 | 1.139 (1.123, 1.155) | < 0.01 |
| NO2 | 9.99 | 0.986 (0.971, 1.001) | 0.07 | ||
| Two-pollutant model including both O3 and NO2 (years 2000–2008) | |||||
| O3 | 421,597 | 804,812 | 11.53 | 1.096 (1.083, 1.108) | < 0.01 |
| NO2 | 9.99 | 1.083 (1.069, 1.098) | < 0.01 | ||
| Units are micrograms per cubic meter for total PM2.5, and parts per billion for gaseous pollutants. 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 in exposure. | |||||