This study seeks to expand and integrate previous research on air pollutants to understand the effect of these environmental contaminants on autism, building on data in the Autism Genetic Resource Exchange (AGRE). Current studies have been limited to specific regions, however, access to AGRE families provides the opportunity to study potential environmental contributors to autism over a broad geographic area, and further creates the potential for gene-environment research. In this study AGRE families will be re-contacted to collect information on residential histories of the parents during pregnancy and early life of each child in the family. Addresses will be geocoded, and air pollution assignments created for each location using Environmental Protection Agency (EPA) databases. These will include HAPs, air quality measurements (including PM), and distance to roadway metrics as an indicator of TRP. Addresses will also be linked to census data to gather important information on demographic and socioeconomic characteristics that may be important to air pollution-autism associations. This study will help in understanding how air pollutants, which are very common environmental exposures, may be part of the puzzle of what causes autism. By linking this environmental data to the existing AGRE data, this will create a resource that can be used for future studies that could include how a person's genetic makeup may increase susceptibility to air pollutants.