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Plastic race tracks, which have become popular at schools around Shanghai City, are raising controversy as to whether they can harm students' health.

The tracks, composed of soil and cement covered with a plastic layer surface, are said to emit poisonous gases when exposed to hot weather and strong light.

Such gases are known to cause dizziness and nausea, medical experts said.

"People inhale up to 30 times as much air as the average level when they do exercises, so the plastic tracks can be particularly dangerous," said Wu Meiyan, a chemist at the Chinese Academy of Sciences.

Wu recommended that schools stop using the tracks at their earliest convenience.

Not everyone, however, is alarmed.

A testing laboratory at East China University of Science and Technology, which conducts frequent experiments on synthetic surfaces, said poisonous components found in the plastic used for tracks have already undergone chemical changes before installation on campus playgrounds.

Experts also point out that exposure to rain cleans plastic materials and diminishes the strength of harmful elements.

Despite the controversy, local schools, for the most part, remain enthusiastic.

According to the Shanghai Education Commission, some 80 percent said they have no plans to abandon synthetic facilities.

"Without authoritative interference, we won't give up the tracks," said Zhou Zhigang, vice principal at Jing'an Foreign Language School, whose school plans to install new tracks this year.

"Plastic surface tracks can greatly secure students' safety, as well as improve the campus environment," said a commission official who only identified himself as Zhao.

Until recently, school tracks were covered with charcoal cinder, which resulted in a great number of athletic injuries because of their course surfaces, said Zhao.

"Student's wounds often become inflamed when coal cinders get into their skin," said Yang Jun, a local sports enthusiast. "Plastic tracks make much more sense."

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