It is good that in our world we have lead from the petrol. Lead is not poisonous to adults. Even a pregnant woman had no problem with it.

But, lead makes only problems to the children, particularly for the school going children. It could reduce their intelligence thus their capacity of learning. There are studies from World Health Organization (WHO) involving hundreds of thousands of school going children which proved these adverse effects.

We have done a great job, but the substitute for lead in petrol, benzene is more dangerous. Up to 5% of benzene is mixed with petrol to get the similar characteristics of the leaded petrol.

Benzene comes out with the exhaust gases to the environment. It is present everywhere now and bad for our health.

Benzene is cancerous but nobody talks about that.

Long-term health effects of exposure to benzene:

• The major effect of benzene from long-term exposure is on the blood. (Long-term exposure means exposure of a year or more.) Benzene causes harmful effects on the bone marrow and can cause a decrease in red blood cells, leading to anemia. It can also cause excessive bleeding and can affect the immune system, increasing the chance for infection.
• Some women who breathed high levels of benzene for many months had irregular menstrual periods and a decrease in the size of their ovaries. It is not known whether benzene exposure affects the developing fetus in pregnant women or fertility in men.
• Animal studies have shown low birth weights, delayed bone formation, and bone marrow damage when pregnant animals breathed benzene.
• The Department of Health and Human Services (DHHS) has determined that benzene causes cancer in humans. Long-term exposure to high levels of benzene in the air can cause leukemia, cancer of the blood-forming organs.

http://www.bt.cdc.gov/agent/benzene/basics/facts.asp

Now-a-days we know continuous environmental exposure is also a great risk for our health.