Prevalence of nickel sensitization and urinary nickel content of children are increased by nickel in ambient air

In a cross-sectional study performed in 2000, an unexpected positive association between nickel (Ni) in ambient air, urinary Ni content and the prevalence of Ni sensitization in a subgroup of 6-yr-old children living near a steel mill was observed. Between 2005 and 2006, in a different and larger study population, we examined if Ni from ambient air or urinary Ni concentration was related to Ni sensitization in children living next to Ni-emitting steel mills.We studied 749 school beginners living in four Ni-polluted industrial areas of North Rhine-Westphalia, Germany. We assessed Ni in ambient air, Ni in urine from children and mothers, and Ni in tap water, conducted patch tests in children (including the NiSO4-dilution test) and collected questionnaire data. Statistics were done by linear and logistic regression analyses, adjusted for covariates.At increased Ni concentration in ambient air (unit of increase: 10 ng/m3), urinary Ni concentrations rose in both mothers (9.1%; 95% CI: 6.8–11.4%) and children (2.4%; 95% CI: 0.4–4.4%). The prevalence of Ni sensitization in children was associated with increased Ni from ambient air (unit of increase: 18 ng/m3; odds ratio 1.28; 95% CI: 1.25–1.32) and urinary Ni concentration (unit of increase: 7.1 μg/L; odds ratio 2.4; 95% CI: 1.20–4.48). Ni in ambient air of areas with Ni-emitting factories contributes to internal Ni exposure in residents via inhalation and, furthermore, is a risk factor for the development of Ni sensitization in children.

Research Highlights
► Hot spots of increased Ni concentration in ambient air near steel mills.
► Elevated Ni concentration in urine from children/mothers living near the steel mills.
► Increased frequencies of Ni sensitization in the children.
► Considerable Ni hypersensitivity at very low NiSO4 test concentrations (patch test).