2.1. Modeling birth outcomes
In order to examine the effect of pollution on health at birth, we restrict the sample to women who lived within 10 km (about 6.2 miles) of a monitor and estimate baseline models of the following form:
where O is a birth outcome, i indexes the individual, j indexes the mother, m indexes the nearest monitor, and t indexes time periods.
The vector Pmt contains measures of ambient pollution levels in each of the first, second, and third trimesters of the mother’s pregnancy, denoted by s, using the monitor closest to the mother’s residence.
We construct the trimester measures by taking the average pollution measure over the trimester,so bs reflects the effect
from a change in mean pollution levels for trimester s.
The wmt represents daily precipitation and daily minimum and maximum temperature averaged over each trimester of the pregnancy.
We control for weather in the vector w because it may have independent effects on birth outcomes and is correlated with ambient pollution levels (Samet et al., 1997).