Association of brominated trihalomethane and haloacetic acid exposure with fetal growth and preterm delivery in Massachusetts.

OBJECTIVES We examined the relationship between adverse reproductive outcomes and exposure to several disinfection by-products including haloacetic acids (HAAs), trihalomethanes (THMs), and the brominated THMs sum (THMBr). METHODS Second- and third-trimester exposure scores were estimated from quarterly town-level average THM and HAA concentration data and were examined relative to mean birth weight (BWT), small for gestational age (SGA), and preterm delivery (PTD). RESULTS We found an increased risk of PTD for second-trimester chloroform, bromodichloromethane, and all HAA exposure metrics (adjusted odds ratio range: 1.04 to 1.15), but detected no associations for SGA and third-trimester exposures. Mean BWT deficits were observed across all HAA (26 to 33 g) and THMBr (11 to 23 g) exposure categories. CONCLUSIONS We detected consistent associations for adjusted mean BWT and THMBr exposures; these data reinforce the need to consider different disinfection by-product exposure metrics in epidemiological studies.