Rubber Antioxidants and Their Transformation Products: Environmental Occurrence and Potential Impact

Abstract

Antioxidants are prevalently used during rubber production to improve rubber performance, delay aging, and extend service life. However, recent studies have revealed that their transformation products (TPs) could adversely affect environmental organisms and even lead to environmental events, which led to great public concern about environmental occurrence and potential impacts of rubber antioxidants and their TPs. In this review, we first summarize the category and application of rubber antioxidants in the world, and then demonstrate the formation mechanism of their TPs in the environment, emphasizing their influence on the ozone oxidative degradation. The potential toxic effects of antioxidants and their TPs are further reviewed to improve understanding of their biological health impact and environmental risks. Finally, the environmental occurrences of antioxidants and their TPs are summarized and their environmental impacts are demonstrated based on the recent studies. Due to the currently limited understanding on the toxic and biological effects of these compounds, further studies are required in order to better assess various TPs of these antioxidants and their environmental impact. To our knowledge, this is the first review on antioxidants and their TPs in the environment, which may elevate the environmental risk awareness of rubber products and their TPs in the near future.

Unanticipated Thio-oxidation of Organophosphite Chemical Additives in PVC Microplastics Following In-Situ Weathering

“…Not surprisingly, TPHP was formed from TPPi in all solutions including the acetonitrile negative control (Figure S2), demonstrating the sulfurindependent oxidation reactions (e.g., ambient ozone or other oxidants). 50,[52][53][54] In summary, these results confirmed TPPi to be a common precursor for TPHP and TPTP, via ozone or other oxidants under non-aqueous conditions as well as sulfur oxidation reactions in water, respectively. To further confirm if thio-oxidation of organophosphites can be observed under environmentally relevant conditions, PVC pellets were incubated with sulfur species in aqueous PBS solution.…”

Synthetic Antioxidants as Contaminants of Emerging Concern in Indoor Environments: Knowns and Unknowns

“…52 Rubber is a major source of the 6PPD pollutant in the environment. 15 Dust has a large specific surface area; this feature makes it have the ability to "adsorb" synthetic antioxidants in the indoor environment (i.e., dust serves as an important reservoir for indoor synthetic antioxidants). Consequently, enabled by its easy sampling and availability, dust has become a popular sample matrix for evaluating indoor contamination caused by contaminants of emerging concern.…”

“…Furthermore, high room temperatures can accelerate the release of chemical contaminants from mattresses to indoor environments . Rubber is a major source of the 6PPD pollutant in the environment . Dust has a large specific surface area; this feature makes it have the ability to “adsorb” synthetic antioxidants in the indoor environment (i.e., dust serves as an important reservoir for indoor synthetic antioxidants).…”

“…3,14 It has been reported that the rubber industry can consume 700,000 tons of synthetic antioxidants per year. 15 Moreover, the global market for synthetic antioxidants in 2022 reached 2.2 billion USD. 16 The most commonly used synthetic antioxidants can be separated according to their structures and functionalities into synthetic phenolic antioxidants (SPAs), amine antioxidants (AAs), and organophosphite antioxidants (OPAs).…”

“…In addition to the above-mentioned contaminants, synthetic antioxidants, a group of contaminants of emerging concern, have attracted increasing concerns in recent years. − Synthetic antioxidants are widely used to inhibit oxidation reactions and protect various products, such as polymers, personal care products, and even foods. , It has been reported that the rubber industry can consume 700,000 tons of synthetic antioxidants per year . Moreover, the global market for synthetic antioxidants in 2022 reached 2.2 billion USD .…”