Hearing loss in children with e-waste lead and cadmium exposure

Highlights: • Higher blood Pb but not urinary Cd was found in the e-waste-exposed children. • Elevated hearing thresholds and hearing loss prevalence in the exposed children were observed. • Child hand-to-mouth behavior was an important factor for Pb and Cd exposure. • Pb showed a significant OR for hearing loss in children by adjusting confounding factors. Environmental chemical exposure can cause neurotoxicity and has been recently linked to hearing loss in general population, but data are limited in early life exposure to lead (Pb) and cadmium (Cd) especially for children. We aimed to evaluate the association of their exposure with pediatric hearing ability. Blood Pb and urinary Cd were collected form 234 preschool children in 3–7 years of age from an electronic waste (e-waste) recycling area and a reference area matched in Shantou of southern China. Pure-tone air conduction (PTA) was used to test child hearing thresholds at frequencies of 0.25, 0.5, 1, 2, 4 and 8 kHz. A PTA ≥ 25 dB was defined as hearing loss. A higher median blood Pb level was found in the exposed group (4.94 ± 0.20 vs 3.85 ± 1.81 μg/dL, p < 0.001), while no significance was found for creatinine-adjusted Cd. Compared with the reference group, the exposed group had a higher prevalence of hearing loss (28.8% vs 13.6%, p < 0.001). The PTA in the left, right and both ears, and hearing thresholds at average low and high frequency, and single frequency of 0.5, 1 and 2 kHz were all increased in the exposed group. Positive correlations of child age and nail biting habit with Pb, and negative correlations of parent education level and child washing hands before dinner with Pb and Cd exposure were observed. Logistic regression analyses showed the adjusted OR of hearing loss for Pb exposure was 1.24 (95% CI: 1.029, 1.486). Our data suggest that early childhood exposure to Pb may be an important risk factor for hearing loss, and the developmental auditory system might be affected in e-waste polluted areas.