Early-life cockroach allergen and polycyclic aromatic hydrocarbon exposures predict cockroach sensitization among inner-city children

Abstract

Background: Sensitization to cockroach is one of the strongest identified risk factors for greater asthma morbidity in low-income urban communities; however, the timing of exposures relevant to the development of sensitization has not been elucidated fully. Furthermore, exposure to combustion byproducts, including polycyclic aromatic hydrocarbons (PAHs), can augment the development of allergic sensitization.

Objective: We sought to test the hypotheses that domestic cockroach allergen measured prenatally would predict cockroach sensitization in early childhood and that this association would be greater for children exposed to higher PAH concentrations.

Methods: Dominican and African American pregnant women living in New York City were enrolled. In the third trimester expectant mothers wore personal air samplers for measurement of 8 nonvolatile PAHs and the semivolatile PAH pyrene, and dust was collected from homes for allergen measurement. Glutathione-S-transferase μ 1 (GSTM1) gene polymorphisms were measured in children. Allergen-specific IgE levels were measured from the children at ages 2, 3, 5, and 7 years.

Results: Bla g 2 in prenatal kitchen dust predicted cockroach sensitization at the ages of 5 to 7 years (adjusted relative risk [RR], 1.15; P = .001; n = 349). The association was observed only among children with greater than (RR, 1.22; P = .001) but not less than (RR, 1.07; P = .24) the median sum of 8 nonvolatile PAH levels. The association was most pronounced among children with higher PAH levels and null for the GSTM1 gene (RR, 1.54; P = .001).

Conclusions: Prenatal exposure to cockroach allergen was associated with a greater risk of allergic sensitization. This risk was increased by exposure to nonvolatile PAHs, with children null for the GSTM1 mutation particularly vulnerable.

Figure 1. Overview of study and children included in analyses

Of the 727 children enrolled prenatally, analyses for the current study was restricted to the n = 349 who had valid measurements for prenatal Bla g2 and PAH and allergen specific IgE measured at age 5 and/or 7.

Figure 2. Prevalence of sensitization to cockroach with tertiles of prenatal Bla g2 in kitchen dust

Tertiles of Bla g2 were defined as follows: low = < 0.73 ng/g, moderate = 0.73–772 ng/g, high = > 772 ng/g. Sensitization was defined as ≥ 0.35 IU/ml IgE to cockroach.

Figure 3. Probability of sensitization to cockroach at age 5–7 with prenatal Bla g2 exposure among children with (A) lower and (B) higher prenatal airborne Σ₈PAH_nonvolatile

Σ₈PAH_nonvolatile concentrations were dichotomized at the median (2.25 ng/m³). Unadjusted logistic regression lines are depicted with 95% C.I. in gray (A. P = 0.34 and B. P < 0.001).

Figure 4. Probability of sensitization to cockroach at age 5–7 with prenatal Bla g2 exposure stratified by prenatal Σ₈PAH_nonvolatile exposure and GSTM polymorphisms

Σ₈PAH_nonvolatile concentrations were dichotomized at the median (2.25 ng/m³). Unadjusted logistic regression lines are depicted with 95% C.I. in gray (A. P = 0.43; B. P = 0.60; C. P = 0.017; D. P = 0.005)