The study is a blinded cross over test of in-home air filtration. Participants will have a window unit air filter (HEPA) installed that will filter for 3 weeks and do sham filtration for another 3 weeks. During the time that the filter is installed in the home a machine that measures particulate air pollution of the type that the filter is designed to remove will be installed. A survey will be administered, blood samples taken and blood pressure measured immediately prior to starting the filter, at 3 weeks when the filtration is changed from sham to real filtration or visa versa and at the end of the second three week period. All participants will be recruited from the Boston Puerto Rican Health Study cohort.