High levels of urinary naphthalene metabolites measured in a sample of California schoolchildren: a call to expand monitoring and identify exposure sources

Introduction: Polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs) are common air pollutants, and many are human toxicants. Naphthalene is one of the most pervasive PAHs and is highly toxic. Children are especially vulnerable to the adverse health effects associated with exposure to these chemicals. Methods: We conducted a pilot study to characterize PAH and VOC exposures to schoolchildren living in a community heavily burdened by air pollution. Sixty-nine urine samples were collected from 18 children attending a school in Stockton, CA, USA in 2021. Participants were between the ages of 5 and 13 and predominantly Hispanic (78%). Samples were analyzed for monohydroxy metabolites of four PAHs, including naphthalene, and mercapturic acid metabolites of six VOCs. Urinary PAH and VOC metabolite levels were compared to the most recent US data available for children from the National Health and Nutrition Examination Survey (NHANES), collected 3-11 years earlier. Results: Naphthalene metabolite levels were nearly three-fold higher than levels in NHANES. Levels for other PAH and VOC metabolites were similar to, or lower than, those in NHANES. Conclusion: Our results are consistent with a small, but growing, body of literature that shows elevated naphthalene exposures in Hispanic/Mexican Americans and suggests overall naphthalene exposures may be on the rise in the US and elsewhere. These exploratory results underscore the need to monitor trends and identify sources of naphthalene exposure.