Maternal exposure to gasoline and exhaust increases the risk of childhood leukaemia in offspring - a prospective study in the Norwegian Mother and Child Cohort Study.

BACKGROUND

In the prospective population-based Norwegian Mother and Child Cohort Study (MoBa), comprising 113 754 offspring, we investigated the association between parental exposure to "gasoline or exhaust", as a proxy for benzene exposure, and childhood leukaemia.

METHODS

Around gestational week 17, mothers and fathers responded to a questionnaire on exposure to various agents during the last 6 months and 6 months  pre-conception, respectively. Benzene exposure was assessed through self-reported exposure to "gasoline or exhaust". Cases of childhood leukaemia (n = 70) were identified through linkage with the Cancer Registry of Norway. Risk was estimated by hazard ratios (HRs) with 95% confidence intervals (95%CI), comparing offspring from exposed and unexposed parents using a Cox regression model.

RESULTS

Maternal exposure to "gasoline or exhaust" was associated with an increased risk of childhood leukaemia (HR = 2.59; 95%CI: 1.03, 6.48) and acute lymphatic leukaemia (HR = 2.71; 95%CI: 0.97, 7.58). There was an increasing risk for higher exposure (p value for trend = 0.032 and 0.027). The association did not change after adjustment for maternal smoking.

CONCLUSION

In spite of rather few cases, the findings in this prospective study, with the exposure metric defined a priori, support previous observations relating maternal exposure to benzene from gasoline and other petroleum-derived sources and the subsequent development of childhood leukaemia in the offspring.