# A toxic burden in Ningbo, Zhejiang Province: elevated heavy metal concentrations in sanitation workers

## TL;DR

Sanitation workers in Ningbo have higher levels of heavy metals in their bodies due to exposure from improperly disposed waste, highlighting a need for better protection.

## Contribution

The study identifies specific heavy metals and their elevated concentrations in different types of sanitation workers, linking them to occupational risks.

## Key findings

- Sanitation workers showed elevated serum levels of Mn, Cd, Sn, and Sb compared to controls.
- Drivers had higher urine levels of As, Cd, and Hg, while operators had increased Cr concentrations.
- Blood concentrations of As, Cd, Hg, and Pb were highest in drivers, indicating job-specific exposure risks.

## Abstract

Sanitation workers are exposed to heavy metals due to improper disposal of waste. This study analyzes heavy metal concentrations in the serum, urine, and blood of sanitation workers exposed to improperly disposed e-waste and industrial residues, and examines how protective measures affect these levels.

This study examines heavy metal levels in 102 sanitation workers (22 operators, 37 drivers, and 43 sanitary workers) versus a control group of 50 unrelated workers. Samples were pre-treated with 0.5% nitric acid and Triton X-100 for serum and blood, and 0.5% nitric acid with 200 μg/L gold for urine. ICP-MS in KED mode was used to measure concentrations of 10 heavy metals (Cr, Mn, Co, Ni, As, Cd, Sn, Sb, Hg, and Pb) in the samples.

Long working hours, working at disposal and hand injury were associated with higher concentrations of Cd, Sb, and Hg in human blood. Elevated serum levels of Mn (2.46 μg/L), Cd (0.14 μg/L), Sn (1.19 μg/L), and Sb (9.99 μg/L) were observed in sanitation workers. Among drivers, increased serum concentrations were noted for Mn (2.67 μg/L), Cd (0.15 μg/L), Sn (1.18 μg/L), and Hg (0.57 μg/L). Serum Sb (10.10 μg/L) was particularly elevated in the sanitary workers. Sanitation workers exhibited heightened urine levels of Cr (1.91 μg/L), Co (0.35 μg/L), Ni (2.79 μg/L), Cd (0.92 μg/L), Sn (6.43 μg/L), and Sb (0.14 μg/L). Operators demonstrated an increased concentration of Cr (2.37 μg/L). Drivers showed elevated levels of As (95.29 μg/L), Cd (1.34 μg/L), Sb (0.14 μg/L), and Hg (0.31 μg/L). Sanitary workers exhibited higher concentrations of Co (0.41 μg/L), Ni (3.54 μg/L), and Sn (6.79 μg/L). Blood concentration levels of As (8.70 μg/L), Cd (3.62 μg/L), Hg (3.82 μg/L), and Pb (16.71 μg/L) were highest in drivers’ group followed by operators, while lowest in sanitary workers. The median concentrations were all below the BEI (ACGIH, GBZ, WS/T).

Sanitation workers face an elevated risk of exposure to heavy metals, may posing significant threats to their occupational health. There is a critical need for comprehensive prevention and intervention strategies to mitigate heavy metal exposure among sanitation workers.