Environmental impact assessment of waste plastic modified asphalt mixtures: VOCs emission characteristics, environmental-health risks, and underlying mechanism.

Incorporating waste plastics into asphalt mixtures offers dual benefits of enhancing performance and reducing white pollution, while also necessitating consideration of their environmental impact. This work quantitatively investigated the effects of waste high-density polyethylene (wHDPE), polyvinyl chloride (wPVC), and polypropylene (wPP) plastics on volatile organic compounds (VOCs) emissions and associated environmental-health risks of asphalt mixtures prepared via the dry method under simulated paving conditions, with mechanistic insights into the impacts. Results revealed that waste plastics could improve high-temperature and water stability. Meanwhile, these selected waste plastics can effectively reduce the total VOCs concentrations of asphalt mixture, with a maximum inhibition rate of 36.72 % by wPP. Alkanes and aldehydes (81.41 % of total VOCs) were decreased by over 30 %. Meanwhile, wPP was the most effective in reducing environmental and health impacts, achieving up to 39.7 %, 33 %, and 27.7 % inhibition of ozone formation potential, secondary organic aerosol formation potential, and cancer risk, respectively. However, the addition of wPVC and high-dose wHDPE increased hazardous emissions such as benzene series and halogenated hydrocarbons due to thermal degradation under high temperature. These findings underscore the importance of waste plastic type/dosage optimization to address performance-environmental trade-offs, providing valuable guidance for sustainable waste plastic reuse in road engineering.