Phelps competes in a sport that has not been seriously tainted by doping, unlike track and field.

菲尔普斯参加的游泳项目的比赛并没有象田径项目一样受到兴奋剂丑闻的严重影响。

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"This field has been tainted with a lot of promises of finding new drugs, but the problem has been that we've had to establish a very good baseline with many large pieces of DNA, " says Eric Mathur, Diversa's senior director of molecular biology.

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Field is the tainted too.

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Track and field is littered with athletes tainted by scandal.

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