Hot weather suggested as possible cause of chemical release that sickened students

A number of students from a Hangzhou-based middle school were sickened recently, and synthetic material used for the running tracks and artificial grass at the school were the suspected culprits.

When a number of samples were sent to a lab, one of the grass samples was found to be emitting toxic benzene more than 14 times above the national safety limit. A second grass sample was found to be above the limit by about 27 percent.