| 1. | Stricter limits on pollution levels must be imposed
要采取更严厉的措施，控制污染程度。 |
| 2. | Pollution levels fall during nightime
夜晚的污染程度则会下降。 |
| 3. | Air pollution level roadside
路边空气污染指数 |
| 4. | Air pollution level
空气污染水平 |
| 5. | Synthetic assessment on pollution level and potential ecological risk of heavy metals in kaozhou bay
考洲洋重金属污染水平与潜在生态危害综合评价 |
| 6. | Physiological and biochemical changes in epiphytic bryophytes under different air pollution levels
大气污染梯度下树木附生苔藓植物生理生化指标的变化 |
| 7. | Pollution levels tend to be at their lowest during spring and autumn when winds are freshest
春秋天时候，风带来新鲜清新的空气。因此，污染程度也最低。 |
| 8. | Many laws require that pollution levels not exceed those found to be harmful to people
许多法律要求污染水平不能超过那些已经发现了的对人们造成危害的水平。 |
| 9. | Another study showed that visits to hospital emergency rooms rose on days with higher pollution levels
另一项研究显示，医院急症人数的多少，与当天的污染程度有关。 |
