Carbon monoxide bonds more strongly to haemoglobin and is not released at the cell. The carboxy-haemoglobin cannot carry oxygen to cells in the body. Even low levels of carbon monoxide can starve the brain of oxygen. A lead compound is often added to petrol to improve its value. Lead compounds are then expelled through the exhaust.
Lead absorbed by the body damages the brain and can cause anti-social behaviour.
It reduces intelligence and powers of concentration. Hydrocarbon Vapour Unburnt petrol and diesel fumes expelled through car exhausts are changed by sunlight to photochemical smog . Smoke and Soot Burning wood or coal produces smoke and soot. Diesel and petrol engines can also produce smoke and soot. The amount of smoke produced depends on the efficiency of the engine.