The synthetic running tracks have been uninstalled. CHINA DAILY

Loopholes

Experts said synthetic running tracks are used across the world, from kindergartens to Olympic stadiums, and they are hazard-free providing they are manufactured and laid in accordance with specific chemical processes and quality-control standards.

Chen Jianding, a professor of materials engineering at East China University of Science and Technology, said improper processing and the use of cheap additives to improve surface resilience could result in an excess of free toluene diisocyanate, an organic compound used in the production of polyurethane foams, that can be toxic to humans.

He said the compound form of TDI, as used in running tracks, has low toxicity.

The national quality standard for synthetic playground surfaces sets no strict limits on the amount of free TDI that can be used and does not specify the types and concentrations of glues and plasticizers, which can also be toxic if mixed incorrectly.

Zhang Jinliang, an environmental safety researcher at the Chinese Research Academy of Environmental Sciences, said the lack of specifications for relevant chemicals in the air-quality monitoring standard means toxins exist even in environments classified as safe after testing.

"This explains most of the cases where post-construction air-quality tests were unable to detect the real toxins affecting students' health on low-quality rubber tracks," she said.

Supervision urged

Industry insiders say the loopholes in standards and the lack of transparent supervision in the bidding process for school construction projects have opened a door for unscrupulous contractors to make a profit at the expense of students' safety.

The cost of safe, high-quality processed surfaces is about 300 yuan ($46) per square meter, according to Liu Haipeng, an official with the National Sports Facility Standardization Committee: "But some manufacturers offer much cheaper products containing excessive amounts of hazardous chemicals to lure education authorities and schools with low budgets."

Liu estimated that about 3,000 private materials manufacturers are operating without the necessary technical certificates, accounting for almost half the market share of the synthetic ground-surface industry.

Liu Dongwei, chief architect at the China Architecture Design and Research Group, urged stricter scrutiny of the bidding processes for such projects.

"Whoever offers the lowest price wins the bid, regardless of quality. It's a common practice. To ensure better quality, the higher-level authorities should strengthen supervision of local education departments in the bidding process, along with the assessment of contractors' qualifications," he said.

Zheng Jinran contributed to this story.