A、Sound volume and exposure time. B、Quality of the portable music players. C、Frequency of listening on a daily basis. D、Soaring

(30)Millions of youngsters across Europe could suffer permanent hearing loss after five years if they listen to MP3 players at too high a volume for more than five hours a week, European Union (EU) scientists warned Monday. The scientists’ study, requested by the European Commission, attacked the concept of "leisure noise," saying children and teenagers should be protected from increasingly high sound levels. "There has been increasing concern about exposure from the new generation of personal music players which can reproduce sounds at very high volumes without loss of quality," the Commission, the EU’s executive arm, said in a statement. (31)"Risk for hearing damage depends on sound level and exposure time," it said. "More and more young people were exposed to the significant threat that leisure noise posed to hearing." Commission experts estimate that between 50 and 100 million people listen to portable music players on a daily basis. (32) If they listened for only five hours a week at more than 89 decibels (分贝), they would already exceed EU limits for noise allowed in the workplace. But if they listened for longer periods, they risked permanent hearing loss after five years. The scientists calculated the number of people in that risk category at between 5% and 10% of listeners, meaning up to 10 million people in the European Union. Sales of personal music players have soared in EU countries in recent years, particularly of MP3 players. Commission experts estimate unit sales between 184 and 246 million for all portable audio devices just over the last four years, of which MP3 players range between 124 and 165 million.
30. What will happen to people listening to MP3 players at too high a volume for a long time?
31. According to the EU statement, what factors decide the risk for hearing damage?
32. What might be the EU limits for noise allowed in the workplace?