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Directed acyclic graph (DAG) representing the relations between ambient (amb superscripts) particulate matter (PM) concentration estimates, personal (pers superscripts) PM exposure estimates, time invariant factors (U) that affect ambient PM, time-varying factors (V) that affect personal PM exposure, and autism spectrum disorders. The subscripts indicate different trimesters of pregnancy. The personal PM exposures are colliders. See text for additional discussion.
