Outdoor carbon monoxide, nitrogen dioxide, and sudden infant death syndrome

Aims: To investigate whether infants who died of SIDS were more likely to have higher acute and lifetime average exposures to outdoor carbon monoxide (CO) and nitrogen dioxide (NO₂) than comparison healthy infants. Methods: A total of 169 case and 169 matched control infants born between 1988 and 1992, were studied. CO and NO₂ concentrations, averaged for all days within the infant's lifespan, and the last 30 days, 7 days, 3 days, and 1 day of life were obtained from air pollutant data provided by the, California Air Resources Board. Results: Based on monthly aggregated data, average CO and particularly NO₂ were associated with SIDS count, even after adjustment for seasonal trends. SIDS outcome was not significantly associated with high average outdoor CO levels for any time period. However, high average outdoor NO₂ levels on the last day of the infant's exposure period were significantly associated with SIDS; the adjusted odds ratio was 2.34 (95% CI 1.13 to 4.87). Conclusions: SIDS may be related to high levels of acute outdoor NO₂ exposure during the last day of life. Further studies are needed to replicate this finding.