Hi, I am working on the topic of the impact of air pollution on Child Health, combining the data from the Demographic Health Survey (DHS) and NASA satellite data imagery. I have used the location from DHS data to calculate the mean PM2.5 for each month and each cluster.

I have to construct a trimester pollution exposure by calculating mean PM2.5 for three month periods preceding month m childbirth. I have to construct a nine-month pollution exposure by calculating mean PM2.5 for nine-month periods preceding month m of childbirth.

how I calculate trimester pollution exposure and nine-month pollution exposure.