Population-based study of l-transposition of the great arteries: possible associations with environmental factors.

BACKGROUND: L-transposition of the great arteries (l-tga) is an uncommon congenital cardiovascular malformation that occurs from abnormal looping of the primitive cardiac tube. Little is known about risk factors for the development of l-tga.

METHODS: This study is a case-control study of 36 cases of l-tga compared to 3,495 population-based live born infant controls in the Baltimore Washington Infant Study (1981-1989 births). Extensive personal and occupational exposure data from parental interviews were available for all subjects. A geographic information system was used to identify potential environmental exposures, for example, hazardous waste sites prioritized for cleanup (National Priority List sites). Adjusted odds ratios (OR) and 95% confidence intervals (CI) were calculated using exact parameter estimates from logistic regression.

RESULTS: Most infants with l-tga had multiple cardiovascular anomalies, with single ventricle in 47%. Over 75% of all cases of l-tga occur in two regions of contiguous cases. Within these regions, the case control OR of l-tga are 13.4 (95% CI, 4.7-37.8) Both areas are characterized by release of toxic chemicals into air and by hazardous waste sites. Parental exposures to hair dye, smoking and laboratory chemicals are also associated with case status.

CONCLUSIONS: L-tga, a congenital cardiovascular malformation due to very early abnormalities in embryogenesis, is associated strongly with residency in two small regions of Maryland and District of Columbia (DC), and with other parental personal or occupational exposures. Additional research is needed to identify the components of spatial and other associations that constitute etiologic risk factors.