Abstract
Tire wear represents a large source of microplastic entering the aquatic environment, however little is known about its environmental risks. Here, we provide the first assessment of the environmental risks of pollution with tire wear microplastic particles (TWP) and associated organic micropollutants present in road runoff in Europe, in one go. Besides microplastic TWP, the assessment focused on priority substances as defined by the Water Framework Directive (WFD). In addition, several other pollutants (mercaptobenzothiazole, tolyltriazole, diisodecyl phthalate and hexa (methoxymethyl)melamine) were included. The risk assessment comprised a hazard identification (selection of traffic related substances), an assessment of exposure (Predicted Environmental Concentrations, PECs), based on estimated and measured values, effect assessment (selection of Predicted No Effect Concentrations, PNECs, and effect values) and a risk characterization (PEC/PNEC and Species Sensitivity Distributions (SSDs)). Whole Effluent Toxicity (WET)-tests on samples taken from road runoff, surface water and sediment were conducted as a retrospective approach to support the risk assessment. We demonstrate that risks exist for TWP and for several TWP-associated chemical substances in surface water and sediment. In addition, WET-tests of the runoff samples showed significant dose-related effects for algae. However, WET-tests of surface water showed no significant toxic effects. The present study provides opportunities to protect the quality of European waters from complex road runoff pollution, focusing on TWP microplastic, their associated WFD priority substances and other hazardous substances.
Highlights
Microplastics are of increasing concern in the environment [1, 2]
For five substances (BaP, Fluoranthene, NP, OP, Di (2-ethylhexyl) phthalate (DEHP)), Environmental Quality Standards (EQS) were available, which apply under the Water Framework Directive (WFD) for surface waters in Europe [96]
We assessed the prospective risk by comparing predicted exposure concentrations of TWPMP particles and 10 organic micropollutants with: 1) limits below which no adverse effects of exposure in the aquatic environment are expected (PEC/Predicted No Effect Concentration (PNEC) ratios), and; 2) by assessing the fraction of species exposed to these concentrations above their No Observed Effect Concentration (NOEC) (PAF)
Summary
Microplastics are of increasing concern in the environment [1, 2]. Tire wear is estimated to be one of the largest sources of microplastics entering the aquatic environment [3,4,5,6,7]. In our study we focus on tire wear particles as a component of (2021) 1:10. Tire components may form toxic transformation products. A previously unknown transformation product of a globally ubiquitous tire rubber antioxidant was identified as the primary causal toxicant for decades of stormwater-linked salmon acute mortality observations in the U.S [35]. Toxicity of TWP leachates is related to the leaching methods used to prepare and extract the tire particles [15]. The acute effect concentrations of TWP leachates (TWP removed) in aquatic media, including marine environments, were found to cover a range of 25 to 100, 000 mg TWP/L [8, 36], while chronic effect concentrations vary from 10 to 3600 mg TWP/L [8]. Components of leachates found to be largely responsible for the toxicity were zinc and organic compounds [17, 26]
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