Caused by the parasitic nematodes Toxocara canis and cati, toxocariasis in humans can result in covert toxocariasis, ocular toxocariasis, visceral larval migrans, and neurotoxocariasis. A common infection, toxocariasis exposure varies widely within and between countries, with a previous estimate of Toxocara seroprevalence using data from 1988 to 1994 in the United States of approximately 13%. Age, poverty, sex, educational attainment, ethnicity, and region have been associated with Toxocara seroprevalence. In this study, we sought to determine the seroprevalence of and factors associated with Toxocara seropositivity in the United States using data from the National Health and Nutrition Examination Survey from 2011 to 2014 to provide a more recent estimate of Toxocara seroprevalence in the United States. We found an overall Toxocara seroprevalence of 5.1%. Increasing age, male sex, low educational attainment, low income, and immigration status each was associated with Toxocara seropositivity. Mexican Americans had reduced odds of exposure. These findings show that exposure to Toxocara continues in the United States and that several demographic factors influence the risk of exposure.

Total brain gray-matter and white-matter volumes can be indicators of overall brain health. Among the factors associated with gray-matter and white-matter volumes is exposure to air pollution. Using data from the UK Biobank, we sought to determine associations between several components of air pollution—PM_2.5, PM_2.5–10, PM₁₀, nitrogen dioxide, and nitrogen oxides—and total gray-matter and total white-matter volumes in multivariable regression models in a large sample of adults. We found significant inverse associations between PM_2.5 concentration and total white-matter volume and between PM_2.5, PM_2.5–10, PM₁₀, nitrogen dioxide, and nitrogen oxide concentrations and total gray-matter volume in models adjusted for age, sex, body-mass index, self-assessment of overall health, frequency of alcohol use, smoking status, educational attainment, and income. These findings of pollutant-associated decreases in total gray-matter and total white-matter volumes are in the context of mean PM_2.5 concentrations near the upper limit of the World Health Organization’s recommendations. Similarly, mean PM₁₀ concentrations were below the recommended upper limit, and nitrogen dioxide concentration was slightly above. Still, there are many areas in the world with much higher concentrations of these pollutants, which could be associated with larger effects. If replicated, these findings suggest that air pollution could be a risk factor for neurodegeneration.