Which one of the following metals pollutes the air of a city having a large number of automobiles?
(1) Cadmium
(2) Chromium
(3) Lead
(4) Copper
Answer: (3) The history of car pollution has been one of air and water contamination followed by regulated improvement. Cars and trucks cause a lot of air pollution in the world today and contribute a lot to the most common and dangerous air pollutants. About 2.3 million tons of lead in lead-acid (Pb) batteries are on the road now. Over 1 million tons of lead is used in making new batteries each year. In the past, motor vehicles were the biggest source of lead. But since leaded gasoline has been phased out, lead emissions have decreased by about 98%. Today, metal processing is the biggest source of atmospheric lead. The highest air concentrations are found in the vicinity of ferrous and nonferrous smelters and battery manufacturers.
