A vendor sells betel leaf wrapped in silver foil in Lucknow, India. AJAY KUMAR SINGH/ASSOCIATED PRESS hide caption

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Researchers have found that the oft-maligned banana peel can grab heavy metals out of polluted water. iStockphoto.com hide caption

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Early morning cigarettes are a proxy for the level of addiction, researchers say. iStockphoto.com hide caption

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A truckload of live turkeys arrives at the Cargill plant in Springdale, Ark., on Aug. 4. Most turkeys in the U.S. are given low doses of antibiotics, which breed resistant strains of bacteria, including Salmonella. Danny Johnston/AP hide caption

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Indian schoolchildren write English alphabets on slates at a primary school outside Hyderabad in June. India is on track to overtake China as the most populous nation in just 16 years. Noah Seelam/AFP/Getty Images hide caption

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Volunteer John Kelley (left) leads an exercise class at a senior center in Oklahoma on Monday. Centers such as these offer seniors a cool place to go during heat waves. Sue Ogrocki/AP hide caption

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Bottles of antiretroviral drug Truvada, a medicine used in trials that showed a reduction in transmission of HIV between heterosexuals. Justin Sullivan/Getty Images hide caption

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