Frequent incidents of toxic polyurethane plastic running tracks have drawn attention

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In recent years, plastic running track issues have been exposed in kindergartens and primary and secondary schools in cities such as Shenzhen, Nanjing, Shanghai, and Beijing. In October 2015, the media reported on the issue of toxic runways harming students ； In June 2016, following cases of symptoms such as nosebleeds, coughing, vomiting, rashes, and red and swollen eyes among children at the Baiyun Road Branch of Beijing No. 2 Experimental Primary School and the Starry Sky Talent Experimental Art Kindergarten in Fengtai District, similar symptoms appeared among students at Beijing Pinggu No. 6 Primary School as well; some of these students were taken to medical facilities where tests revealed abnormal blood counts and positive antibodies for Mycoplasma pneumoniae. Regarding the above issues, parents largely suspect that it is related to the new plastic running tracks installed by the school, once again bringing the issue of toxic running tracks to the forefront of public attention. Half a year later, the problem of toxic running tracks has still not been fully resolved, and the national standards that people are awaiting have not been established. This has led to fear and anger among the general public regarding plastic running tracks, prompting discussions about substandard production quality, inadequate supervision during construction, and aggressive bidding at low prices. Why do plastic running tracks become toxic? Plastic running tracks, also known as all-weather athletics tracks, can be roughly divided into two categories: polyurethane cast-in-place type and pre-made rubber sheet type. Prefabricated types are mainly made from materials such as rubber; they are environmentally friendly products. However, due to their high cost, they are not widely used in China ； Polyurethane accounts for 95% of the domestic market, and the runways and sports fields that are having problems at present are of this type. A plastic running track is made by laying multiple layers of materials one on top of another. Plastic running tracks feature good levelness, high compressive strength, appropriate hardness and elasticity, as well as stable physical properties. These characteristics facilitate athletes’ performance in terms of speed and technique, help to improve athletic results, and reduce the risk of injuries. Therefore, as living standards have improved, plastic running tracks, which were previously used only in professional sports venues, have become commonly installed in the playgrounds of schools of all sizes over the past decade. At the same time, there has been an increase in incidents involving toxic running tracks. Polyurethane plastic running tracks are mainly composed of polyurethane prepolymer, mixed polyethers, recycled tire rubber, EPDM rubber particles or PU particles, pigments, additives, and fillers. The basic raw materials are polyether polyols and polyisocyanates (primarily TDI). The current process is generally a two-component process. That is, at the raw material factory, a prepolymer with isocyanate end groups (Component A) is produced by reacting an excess of polyisocyanate (mainly TDI) with polyether polyol, while Component B is prepared by mixing polyether polyol, inorganic fillers, pigments, catalysts, and other additives. However, considering the toxicity of its raw materials, polyurethane prepolymers used in the production of plastic running tracks are primarily made from elastomeric polyethers. Elastomeric polyethers are colorless or pale yellow, viscous, transparent liquids with relatively stable properties; they have a slight distinctive odor, are non-toxic, non-corrosive, and exhibit good solubility with most organic substances. They are not flammable or explosive. Therefore, there is no significant toxicity either. TDI is a colorless and transparent liquid with an irritating odor; it is an excellent polyurethane material. It can catch fire when exposed to heat, open flames, or sparks; it releases toxic substances—** and nitrogen oxides only when heated or burned. If the technology is up to standard and strict supervision is in place, high-quality TDI polyurethanes that have undergone adequate reaction should be safe. The irritating odor of plastic running tracks mainly stems from chlorides that may be present in the polyurethane (PU) adhesive, residual free diisocyanate (TDI), residues of certain solvents (such as toluene and xylene), residual organic lead, sulfides remaining in the black particles, bromobenzene-based additives, and other such substances. If these substances exceed the allowed levels, they can cause dizziness, vomiting, fainting, cancer, and breathing difficulties, posing a fatal threat to humans, animals, plants, and the environment. According to the \"Risk Monitoring and Analysis Report on Volatile Hazardous Substances in Polyurethane Plastic Sports Venues,\" analysis of the sources of risk shows that harmful chemicals such as benzene, toluene, xylene, formaldehyde, and TDI in these plastic venues originate primarily from raw materials like adhesives, solvents, and black particles. Moreover, contractors, in an effort to cut costs, illegally add organic solvents containing toluene and xylene, which is the main reason why low-quality plastic sports venues are toxic ； Furthermore, unscientific formulations and construction methods can also lead to excessive levels of harmful substances. This shows that during the production of raw materials, some small workshops and even enterprises fail to meet quality standards; in order to achieve high profits, they engage in illegal practices by using substandard materials, which leads to the widespread use of recycled polyethers, industrial paraffins, drying agents and other low-quality raw materials in an attempt to cut costs, thereby causing chaos in society ； Furthermore, during the construction process, the overall quality of the construction teams varies greatly; their professional skills are generally low. The supervision by third-party inspection agencies is insufficient, which leads to construction workers using large amounts of diluents (such as toluene, xylene and other diluents with strong odors and high toxicity, as well as turpentine and gasoline) in order to simplify the work. They also add cheap inorganic fillers, resulting in the frequent production of substandard products that are highly toxic and polluting. Furthermore, some school campuses have been reported to have \"toxic running tracks\"; why were their test results deemed satisfactory? One reason is that domestic environmental protection standards have failed to keep up with the times. The emergence of toxic running tracks is due to the addition of extra materials such as polycyclic aromatic hydrocarbons, substances that have been classified as carcinogens by the International Agency for Research on Cancer, and for which the EU has imposed strict restrictions. The standards applicable in our country regarding plastic running track products are sports standards and environmental protection standards. Such as GB/T 22517.6-2011 \"Requirements and test methods for the use of sports venues – Part 1: Athletics venues\", and GB/T 14833-2011 \"Synthetic material running surface layers\". Both standards specify limits for toxic and harmful substances in finished plastic running tracks; these substances include benzene, toluene + xylene, free toluene diisocyanate (TDI), lead, cadmium, chromium, and mercury. It also specifies physical properties such as impact absorption, skid resistance, and tensile properties. However, there are still no relevant **standards** in place regarding the impact of plastic running tracks on air quality, the quality requirements for the air above such tracks, or the testing of other toxic substances that may be added. Previously, Shenzhen’s \"Quality Standards for the ‘Surface Layer’ of Synthetic Material Sports Venues\" (hereinafter referred to as Shenzhen’s \"Standards\") also began to solicit feedback. In May, Shenzhen’s ‘Standard’ entered the trial phase, with the potential to completely resolve issues related to runway pollution and the so-called \"toxic runways\" problem. On June 7, 2016, the Shanghai Quality and Technical Supervision Bureau announced that China’s first group standard for plastic running tracks, namely \"Limits on Hazardous Substances in Plastic Surfaces of School Sports Venues,\" had been approved for registration. This standard aims to set limits on the release of toxic and harmful substances as well as to regulate aspects such as the inspection and acceptance process of running tracks. At present, revisions to the national standards for plastic running tracks are being considered. In light of the various problems caused by toxic running tracks, as a member of the public, I truly hope that **the relevant authorities will enact appropriate laws and regulations at every stage, from the initial planning phase all the way to the completion of the running tracks. Based on the needs of social development and the feedback received from the implementation of relevant standards, the detailed rules for national standards are continuously revised to crack down on illegal activities, eliminate all forms of pollution, and restore a clean and safe running track for the children in schools.