Previously, we reported that prenatal exposures to polycyclic aromatic hydrocarbons (PAH) and postnatal environmental tobacco smoke (ETS) in combination were associated with respiratory symptoms at ages 1 and 2 years. Here, we hypothesized that children exposed to both prenatal PAH and ETS may be at greater risk of asthma and seroatopy at ages 5–6 years, after controlling for current pollution exposure.

Prenatal PAH exposure was measured by personal air monitoring over 48 h. ETS exposure, respiratory symptoms and asthma at ages 5–6 years were assessed through questionnaire. Immunoglobulin (Ig) E was measured by Immunocap.

A significant interaction between prenatal PAH and prenatal (but not postnatal) ETS exposure on asthma (p < 0.05), but not IgE, was detected. Among children exposed to prenatal ETS, a positive nonsignificant association was found between prenatal PAH exposure and asthma (OR 1.96, 95% CI [0.95–4.05]). Among children without exposure to prenatal ETS, a negative nonsignificant association was found between prenatal PAH exposure and asthma (OR 0.65, 95% CI [0.41–1.01]). Prenatal PAH exposure was not associated with asthma or IgE at age 5–6 years.

Combined prenatal exposure to PAH and ETS appears to be associated with asthma but not seroatopy at age 5–6. Exposure to PAH alone does not appear associated with either asthma or seroatopy at age 5–6 years. Discerning the differential effects between ETS exposed and ETS nonexposed children requires further study.