1.   Electric vehicles would introduce lead releases to reduce urban ozone, a lesser problem.

2.   A recent study by the National Research Council found that MTBE is more effective than ethanol in reducing ozone, a major component of smog.

3.   But tests found that MTBE did more to reduce ozone than an ethanol blend.

4.   But the overall impact of either additive on reducing ozone is very small, the study says.

5.   Reformulated gasoline has many components other than oxygen additives that help reduce ozone.

6.   The rules are aimed at sharply reducing ozone, a component of smog, and controlling tiny airborne flecks of dust and soot called particulate matter.

7.   The Society also reports that ozone has been reduced by only a few percentage points over North America.

8.   The study did not question the overall effectiveness of reformulated gasoline in reducing ozone, a component of urban smog.