Prenatal exposure to butylbenzyl phthalate and early eczema in an urban cohort

Abstract

Background: Recent cross-sectional studies suggest a link between butylbenzyl phthalate (BBzP) in house dust and childhood eczema.

Objectives: We aimed to evaluate whether concentrations of monobenzyl phthalate (MBzP), the main BBzP metabolite in urine, during pregnancy are associated prospectively with eczema in young children, and whether this association varies by the child's sensitization to indoor allergens or serological evidence of any allergies.

Methods: MBzP was measured in spot urine samples during the third trimester of pregnancy from 407 African-American and Dominican women residing in New York City in 1999-2006. Repeated questionnaires asked mothers whether their doctor ever said their child had eczema. Child blood samples at 24, 36, and 60 months of age were analyzed for total, anti-cockroach, dust mite, and mouse IgE. Relative risks (RR) were estimated with multivariable modified Poisson regression. Analyses included a multinomial logistic regression model for early- and late-onset eczema versus no eczema through 60 months of age.

Results: MBzP was detected in > 99% of samples (geometric mean = 13.6; interquartile range: 5.7-31.1 ng/mL). By 24 months, 30% of children developed eczema, with the proportion higher among African Americans (48%) than among Dominicans (21%) (p < 0.001). An interquartile range increase in log MBzP concentration was associated positively with early-onset eczema (RR = 1.52 for eczema by 24 months; 95% confidence interval: 1.21, 1.91, p = 0.0003, n = 113 reporting eczema/376 total sample), adjusting for urine specific gravity, sex, and race/ethnicity. MBzP was not associated with allergic sensitization, nor did seroatopy modify consistently the MBzP and eczema association.

Conclusions: Prenatal exposure to BBzP may influence the risk of developing eczema in early childhood.

Figure 1

Relative risk estimates of child ever-eczema for an IQR increase in prenatal log MBzP urinary concentration (IQR is 1.7 log units, 5.7–31.1 ng/mL), adjusting for specific gravity, race/ethnicity, and sex from separate modified Poisson regression models using questionnaire data collected in person or by telephone interview at 12 different ages.

Figure 2

Association between prenatal urinary concentration of MBzP and report of eczema by 24 months from a multivariable logistic regression adjusted with mean specific gravity and sex. The y-axis is shown on the logit scale and labeled with the corresponding predicted probabilities. The x-axis is shown on a log scale and labeled with the corresponding concentrations. The overall cohort model is shown (black) with 95% CI (gray); the exposure distribution for all participants reporting (top) and not reporting (bottom) eczema is shown with horizontal box plots. The ethnic subsets are shown in dashed and dotted lines for African Americans and Dominicans, with individual observations shown at their urinary concentration as triangles and circles, respectively. Although the baseline probabilities differ in the two subsets, the overall association remains positive, with increasing urinary concentrations of MBzP.