Crack addicts consume the drug on a street in Sao Paulo March 20, 2012. Many Brazilian cities now have their own "cracklands," areas of the city where swarms of crack users have converted entire neighborhoods into nocturnal encampments doubling as open-air crack markets. At nightfall throngs of stupefied buyers crowd around dealers before skulking away behind the telltale glow of cigarette lighters. Sociologists, health experts, and law enforcement officials all agree that crack use is a rapidly growing problem that puts Brazil squarely in the center of the international drug trade, just a few years ahead of the 2014 World Cup and 2016 Olympic Games. Picture taken March 20, 2012. To match Feature BRAZIL-CRACK/ REUTERS/Paulo Whitaker (BRAZIL - Tags: DRUGS SOCIETY POLITICS CIVIL UNREST CRIME LAW) ATTENTION EDITORS - PICTURE 17 OF 24 FOR PACKAGE '24-SEVEN, CRACK IN BRAZIL'