When Oakland High School in California moved into a new building, the students and teachers1 a strong smell. Then almost half of the students began to have a headache and a cough. Experts (专家) came to find the cause of the sickness. Finally, they discovered that the air in the building was not safe to breathe. They were surprised to find out that the desks and chairs in the school library caused the trouble. These desks and chairs were 2 of particleboards(合成板). This kind of board is cheap 3 it is made of very small pieces of wood held together with a chemical. This is just one example of a modern problem that is most4 in cities—indoor air pollution.
A recent study 5 a surpring conclusion: Indoor air pollution is 6 two to five times worse than outside pollution. So remember to open the windows and don't stay too long in modern buildings with windows closed.
