Association of phenol exposure during pregnancy and asthma development in children: The Japan Environment and...

Alkylphenols can originate from numerous products containing alkylphenol ethoxylates, including cleaning products, household items, and cosmetics. Some phenols, such as nonylphenol, are known to be endocrine disruptors, and exposure to them is thought to have contributed to the recent increase in allergic diseases such as asthma. However, the impacts of prenatal phenol exposure on asthma development in children are still unclear.

We analyzed the association between maternal urinary phenol concentrations during early pregnancy and the development of asthma in children at the age of 4, using data from the Japan Environment and Children's Study (JECS), a large-scale nationwide birth cohort study.

We recruited 3,513 pairs of mothers and children participating in the Sub-Cohort Study of JECS. We measured 24 phenols, including nitrophenol, parabens, bisphenol, octylphenol, and nonylphenol, in urine samples taken during the first trimester of pregnancy. The urinary levels of these phenols differed markedly, and some showed a broad spectrum of distribution. Methylparaben was detected at high levels in almost every participant (267.7 ng/ml, standard deviation 433.78). Logistic regression analysis revealed that the odds ratio of asthma onset for high exposure to butylparaben was 1.54 (95% confidence interval: 1.11-2.15). Additionally, logistic regression analysis by gender revealed an asthma development odds ratio of 2.09 (95% confidence interval: 1.20-3.65) for males and 0.65 (95% confidence interval: 0.25-1.70) for females born to mothers in whom 4-nonylphenol was detected, suggesting a gender difference.

Our current analysis using large cohort data suggests that high exposure to butylparaben and low exposure to 4-nonylphenol during pregnancy are risk factors for asthma development in children. These findings establish a valuable foundation for formulating recommendations about prenatal phenol exposure.