Four-year population exposure study: Implications for the effectiveness of e-waste control and biomarkers of e-waste pollution.

E-waste pollution has emerged as a significant environmental concern. To assess the impact of e-waste control on human pollutant exposure risk and identify appropriate biomarkers to classify e-waste pollution levels, we performed longitudinal population exposure monitoring research in an e-waste recycling area in China after e-waste control. The urinary levels of oxidative stress markers and typical pollutants emitted during e-waste recycling, including heavy metals, polycyclic aromatic hydrocarbons (PAHs), and volatile organic compounds (VOCs), were continuously monitored in the surrounding population (including 275 children and 485 adults) from 2016 to 2019 using high-performance liquid chromatography-tandem mass spectrometry and inductively coupled plasma-mass spectrometry. The results showed that exposure to PAHs, VOCs and heavy metals was significantly associated with oxidative stress levels in urine. After e-waste control, the exposure levels of most PAHs and VOCs and a few heavy metals in the population significantly decreased. Interestingly, the level of 8-hydroxy-2'-deoxyguanosine (a biomarker of oxidative DNA damage) in children significantly decreased by 17.6 %, from 9.45 μg/g CRE in 2017 to 7.79 μg/g CRE in 2019 (p < 0.01). Thus, implementing e-waste control measures effectively reduced the human exposure risk to e-waste pollutants. Urinary tin (Sn), s-phenylmercapturic acid (PMA), 2-&3-hydroxyfluorene (2-&3-OHF), 3-hydroxyphenanthrene (3-OHPhe), and 1-hydroxypyrene (1-OHP) levels decreased significantly and monotonically over time (p < 0.01). The levels of urinary Sn and PMA in combination with 1-OHP, 2-&3-OHF, or 3-OHPhe as biomarkers demonstrated an excellent ability to classify e-waste pollution. These biomarkers will facilitate evaluations of the effectiveness of the governmental pollution regulations and policy measures. Additionally, children were generally exposed to higher levels of heavy metals and VOCs and suffered higher levels of oxidative stress damage than adults, suggesting that children are more vulnerable to e-waste pollution. This work will provide a reference for e-waste management and control.