The pollution risk comes from lead derived from fuels, old water pipes and paint.

污染风险来自于燃料、旧水管和油气中的铅。

Delhi has pollution that was ten times those of London. Even there, people would have to cycle 5 hours a week before the pollution risks outweigh the health benefits.

德里的污染水平是伦敦的十倍。即使是在那里，人们每周骑自行车五小时以上，污染的危害才会超过健康功效。