Separate and joint effects of tranplacental and postnatal inhalatory exposure to polycyclic aromatic hydrocarbons: prospective birth cohort study on wheezing events.

The goal of this epidemiologic investigation was to analyze the associations between prenatal and postnatal exposure to airborne polycyclic aromatic hydrocarbons (PAH) and severity of wheeze and recurrent wheeze. The 257 children included in this analysis had a complete set of prenatal and postnatal PAH measurements and attended regular health checkups over a 4-year follow-up period since birth. Transplacental PAH exposure was measured by personal air monitoring of the mothers during the second trimester of pregnancy; postnatal exposure was estimated using the same instruments indoors at the children's residences at age 3. Chemical analysis tests were performed to determine airborne concentrations of nine PAH compounds. The results show that both prenatal and postnatal exposure were associated positively with the severity of wheezing days and recurrent wheezing reported in the follow-up. While the incidence rate ratio (IRR) for severity of wheeze and prenatal PAH exposure was 1.53 (95%CI: 1.43-1.64) that for postnatal PAH exposure was 1.13 (95%CI: 1.08-1.19). However, recurrent wheezing was more strongly associated with airborne PAH levels measured at age 3 (OR = 2.31, 95%CI: 1.26-4.22) than transplacental PAH exposure (OR = 1.40, 95% CI: 0.85-2.09), but the difference was statistically insignificant. In conclusion, it appears that prenatal PAH exposure may precipitate and intensify early onset of wheezing symptoms in childhood, resulting from the postnatal exposure and suggest that success in reducing the incidence of respiratory diseases in children would depend on reducing both fetal and childhood exposure to air pollution.