INVESTIGATING HAZARDOUS AIR POLLUTANTS IN RELATION TO AUTISM SPECTRUM DISORDERS

Abstract

ISEE-554 Introduction: The number of cases of autism appears to be increasing dramatically, but the causes remain largely unknown, raising concern that environmental factors may play a role. Substances that are known or suspected to affect neurodevelopment may be important, as well as those that interfere with the endocrine system during fetal development. We are linking data compiled by the USEPA on hazardous air pollutants (HAPs) to our autism surveillance system data to investigate possible associations between autism and prenatal exposures. Methods: As part of a national CDC-sponsored network, we are conducting multi-source surveillance of autism spectrum disorders (ASD) among children born in 1994 in six counties. For this project we include initial cases ascertained from the state Department of Developmental Services and the Kaiser Permanente Medical Care Program. Liveborn controls are selected from linked birth-infant death vital records, frequency matched to cases by gender and month of birth, in a 2:1 ratio. Address at birth, as recorded on the birth certificate, is geo-coded to obtain census tract for linkage. The USEPA has estimated outdoor air concentrations of various HAPs by census tract nationwide, based on modeling emission inventory and meteorological data. We used the 1996 database, because it is closest to 1994, which includes 33 pollutants. Results: We ascertained about 350 ASD cases and selected appropriate controls, so over 1000 births are included. The cases were predominantly male (82%), as expected. By race, the sample includes 63% Whites, with cases slightly more likely to be Asian or Black than controls. Parents of cases were less likely to be young or to have only a high school education than control parents. We identified HAPs with known or suspected neurotoxicity or developmental toxicity, and assessed whether there was variation in concentration across the 1228 census tracts in the region. This yielded 16 compounds, including heavy metals, volatile organic compounds, and PAH’s. We will examine categorical levels of the pollutants, individually and grouped by type, by demographic factors from the birth certificate and case-control status. Odds ratios will be calculated, including adjustment for selected factors. Discussion: This study efficiently addresses issues of great concern, namely investigating the potential environmental risk factors associated with autism and the health effects of urban air pollution. We are using methodology consistent with environmental health tracking programs.