Families with at least one asthmatic child participating in a cohort recruited by the Pediatric Environmental Medicine Center (PEMC) at Pittsburgh Children's Hospital were invited to participate in the study.Twenty-one homes in and around the Braddock and Clairton communi- ties were sampled for one week during both a summer (July 25th to September 13th, 2011) and winter (January 30th to March 5th, 2012) sampling session. For spatial contrast, six convenience sample homes were recruited from neighborhoods further from the industrial sites. The study area containing the homes was selected within the previously-sampled outdoor monitoring domain, enabling develop- ment of spatio-temporal home-specific outdoor estimates, detailed below.