Worker exposure to pathogens in leachate from municipal solid waste facilities: A multi-scenario, multi-pathogen, and multi-pathway QMRA framework.

Leachate from different municipal solid waste (MSW) facilities serves as a significant reservoir and a dissemination hub for pathogenic microorganisms, which can pose significant health risks to on-site sanitation workers. In this study, a quantitative microbial risk assessment (QMRA) framework based on Monte Carlo simulation was used to evaluate and compare the health risks for sanitation workers exposed to various pathogens in leachate. To this end, digital PCR (dPCR) was employed to measure pathogen concentrations in leachate from 33 MSW facilities across China. Results showed that the estimated median annual infection risks were highest for Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), exceeding risks from other pathogens by 0-6 orders of magnitude. The fresh leachate from waste storage rooms, waste transfer stations, and incineration plants consistently showed higher annual infection and illness risks than landfill leachate. The probability of ungloved hand-to-mouth contact pathway was higher than that of the splashing and gloved hand-to-mouth contact pathways. Latex glove usage reduced the median annual infection risks of pathogens by 0%-90.3%. The sensitivity analysis revealed that the hourly frequency of hand-to-mouth contact and the volume of ingested leachate were the most influential parameters for the hand-to-mouth and splashing exposure pathways, respectively. Overall, the QMRA model of leachate for multi-scenario, multi-pathogen, and multi-pathway risks can aid waste management authorities in adopting effective risk mitigation strategies for sanitation workers.