Where the rubber meets the road: Emerging environmental impacts of tire wear particles and their chemical cocktails.

About 3 billion new tires are produced each year and about 800 million tires become waste annually. Global dependence upon tires produced from natural rubber and petroleum-based compounds represents a persistent and complex environmental problem with only partial and often-times, ineffective solutions. Tire emissions may be in the form of whole tires, tire particles, and chemical compounds, each of which is transported through various atmospheric, terrestrial, and aquatic routes in the natural and built environments. Production and use of tires generates multiple heavy metals, plastics, PAH's, and other compounds that can be toxic alone or as chemical cocktails. Used tires require storage space, are energy intensive to recycle, and generally have few post-wear uses that are not also potential sources of pollutants (e.g., crumb rubber, pavements, burning). Tire particles emitted during use are a major component of microplastics in urban runoff and a source of unique and highly potent toxic substances. Thus, tires represent a ubiquitous and complex pollutant that requires a comprehensive examination to develop effective management and remediation. We approach the issue of tire pollution holistically by examining the life cycle of tires across production, emissions, recycling, and disposal. In this paper, we synthesize recent research and data about the environmental and human health risks associated with the production, use, and disposal of tires and discuss gaps in our knowledge about fate and transport, as well as the toxicology of tire particles and chemical leachates. We examine potential management and remediation approaches for addressing exposure risks across the life cycle of tires. We consider tires as pollutants across three levels: tires in their whole state, as particulates, and as a mixture of chemical cocktails. Finally, we discuss information gaps in our understanding of tires as a pollutant and outline key questions to improve our knowledge and ability to manage and remediate tire pollution.

Regulatory Role of Chinese Herbal Medicine in Regulated Neuronal Death.

Ischemic neuronal injury results from a complex series of pathophysiological events, including oxidative, excitotoxicity, inflammation and nitrative stress. Consequently, many of these events can induce cell death, including necrosis (unregulated cell death) and apoptosis (a type of regulated cell death). These are long-established paradigms to which newly discovered regulated cell death processes have been added, such as necroptosis (a regulated form of necrosis) and autophagydependent cell death. Moreover, many researchers have targeted products associated with Chinese herbal medicine at regulated pathways for the treatment of ischemic neuronal injury. In East Asia, these drugs have been known for centuries to protect and improve the nervous system. Herbal extracts, especially those used in Chinese herbal medicine, have emerged as new pharmaceuticals for the treatment of ischemic neuronal injury. Here, we review the evidence from preclinical studies investigating the neuroprotective properties and therapeutic application of Chinese herbal medicines (Chinese herbal monomer, extract, and medicinal compounds) and highlight the potential mechanisms underlying their therapeutic effects via targeting differently regulated cell death pathways. Notably, many herbs have been shown to target multiple mechanisms of regulated cell death and, in combination, may exert synergistic effects on signaling pathways, thereby attenuating multiple aspects of ischemic pathology. In this review, we summarize a generally regulated pathway of cell death as a target for novel natural herbal regimens against ischemic neuronal injury.