Association between size-resolved PM₁₀-bound heavy metal and metalloid exposure and oxidative stress among waste recycling workers

Following the sharp increase in global waste generation, heavy metals and metalloids (HMMs) have become a serious threat to workers in the waste recycling industry. However, our understanding of internal exposure levels of HMMs and the relationship between size-resolved particulate matter (PM)-bound HMMs external exposure with internal exposure and oxidative stress among waste recycling workers are limited. Therefore, we collected first morning void urine samples from 20 participants and size-resolved indoor PM₁₀ samples at least 45 consecutive days. We then detected 21 urinary HMMs, PM₁₀-bound HMMs and oxidative stress biomarkers (OSBs) of DNA (8-hydroxy-2'-deoxyguanosine [8-OHdG]) and lipids [malondialdehyde (MDA)]. The intraclass correlation coefficients for most HMMs and OSBs ranged from fair to excellent. Linear mixed model analysis showed that urinary HMMs were predominantly affected by warehouse PM_1.1-2.1 and PM_3.3-4.7 HMM inhalation (p < 0.05). Participant 8-OHdG levels were correlated with PM_0.43-10 HMM inhalation, particularly in the ranges of PM_0.43-0.65, PM_4.7-5.8, and PM_9.0-10, with every unit increase in the ln-transformed average daily intake (ADI) generating a 4.30-28.0% increase in urinary 8-OHdG (p < 0.05). Furthermore, MDA levels were generally correlated with PM_0.43-2.1 HMM inhalation (p < 0.05), especially in the PM_0.43-0.65 range, with each unit increase in the ln-transformed ADI generating a 8.5-24.1% increase in urinary MDA. This study reveals the fair to excellent long-term reproducibility of urinary HMM and OSBs and the association between high-level PM-bound HMM exposure and early health impairment for an actual working environment.