ReTIRE: Research on Transformations, Implications, and Risks of End-of-life tires

Northeastern University, Boston MA

Investigators

Abstract

Four million tons of end-of-life tires (ELTs) are generated annually in the USA. Significant amounts of waste tire rubber are repurposed as ground rubber, used in pavement, or sent to landfills. Currently in the USA there are more than 13,000 artificial turf fields filled with crumb rubber and 50 million unmanaged scrap tires exposed to sunlight and other weathering phenomena. This causes the breakdown of ELTs resulting in emissions of chemicals, some of which have ecological toxicity in soil and water environments. There are considerable gaps in our knowledge of the occurrence, transformation, and release of toxic chemicals from ELTs. This study will help address these gaps by identifying chemicals released from ELTs and assessing their environmental behavior. This will be achieved using state-of-the-art chemical analysis techniques in controlled laboratory and field studies. The results will allow us to assess the release and transformation of chemicals from ELTs and characterize their occurrence in the environment. Results will be used to benefit society by informing effective waste tire management practices and help develop environmentally friendly products. Further benefits to society will result from collaboration and training of citizen scientists to enhance scientific literacy and empower citizen scientists with knowledge and skills in environmental chemistry. Recent studies have demonstrated that tire rubber-derived chemicals such as 6PPD-quinone are both ecotoxic and prevalent in the environment. This project is built on the hypothesis that yet to be identified rubber-derived chemicals are released during the ELT aging process, and these chemicals contribute to the environmental mobility, bioaccessibility, and ecotoxicity of ELT materials. Research will focus on identifying the transformation products of ELT aging in controlled laboratory conditions and in the field. High-resolution mass spectrometric analysis of environmental samples will be compared to reference chemicals and existing databases to identify and quantify both known and unknown reaction products at artificial turf fields, tire disposal piles, and underwater reefs. Simulated aging studies will utilize similar analytical methods for three types of waste rubber samples - cryo-milled new tire rubber, mixtures of new/used tire rubber, and new crumb rubber from artificial turf. Aging of samples under simulated solar radiation will be used to investigate the effect of light on product generation at different stages of sample aging. Simulated oxidation/ozonation experiments will assess the reaction kinetics of product formation. Rooftop aging experiments will simulate natural aging under real conditions via integration of the combined effects of sunlight, precipitation, temperature, and atmospheric oxidation. Results will be used to understand i) water leaching potential, ii) ELT product bioaccessibility; iii) in vitro toxicity, and iv) effect-directed analysis of sample extracts exhibiting high ecotoxicity to identify causal chemicals. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.