| 1 | The two main classes of petrochemicals are olefins and aromatics. | |
| 2 | Also, PAHs may affect the fetus' DNA directly. | |
| 3 | In urban areas motor vehicles are a major source of PAHs. | |
| 4 | The good news, Perera said, is that levels of PAHs are declining in New York City. | |
| 5 | There is no evidence that the PAHs affected her daughter' s IQ. |