In the twenty years that the Clean Air Act has mandated unleadedgas use in the United States, the lead accumulation worldwide has decreased significantly.
在《清洁空气法案》强制要求美国使用无铅气体的二十年里，铅在世界范围内的累积量显著下降。
2
All new cars, too, are built so that they can only take unleadedgas.
同时，所有的新型车都只能加无铅汽油。
3
In the twenty years that the Clean Air Act has mandated unleadedgas use in the United States, the lead accumulation world-wide has decreased significantly.