During the last twenty years there has been increasing concern with the quality of the environment. Along with air and water pollutions, noises pollution has been recognized as a serious pollutant. As noise levels have risen, the effects of noise have become more apparent. Noise is defined as "unwanted sound". Causes of noise pollution include traffic, aircraft, rock bands, barking dogs, televisions, garbage trucks, and noise from neighbors, voices, alarms, and watercrafts. Studies show that over forty percent of Americans are disturbed at home or lose sleep because of noise pollution. Noise has bad effects on people and the environment. Noise causes hearing loss, interferes (妨碍) with human activities at home and work, and is in various ways dangerous to people's health and well being. When we think, talk, listen to music, or sleep, we need quiet. Even low levels of noise can be  annoying or frustrating. Sudden increases in volume can make sounds annoying. The quieter the background is, the more penetrating a noise can be.Noise can also make instructions or warning unclear, resulting in accidents. Louder noise bursts can be more disruptive (破坏性).Continued stress can lead to high blood pressure, which is the major cause of some diseases. Long exposure to noise levels above eight-five decibels (分贝) can damage inner cells and lead to hearing loss. Noise can result in the involuntary fear response and can cause adrenaline (肾上腺素) to be pumped into the bloodstream, the heart rate to quicken, muscles to tense, breathing to increase, and the digestive system to slow down. Local government has the responsibility to fight noise pollution. For example, it can regulate the speed of trains through their community. On the other hand, a responsible citizen will never make noise pollution wherever he is. 小题1: How many kinds of environmental pollution are mentioned in the text?
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