Uzuri Pease-Greene, right, leads a walk through the public housing complex in the Potrero Hill neighborhood of San Francisco where her family lives. She is working to have the old buildings replaced. Talia Herman for NPR hide caption

itoggle caption Talia Herman for NPR

Abortion-rights opponent Brian Normile of Beavercreek, Ohio, holds up a poster during a prayer vigil outside Planned Parenthood in Washington, D.C., in January. Alex Wong/Getty Images hide caption

itoggle caption Alex Wong/Getty Images

Chris Newman, seen at her home in Los Molinos, Calif., calls the change she helped get made to lung cancer treatment guidelines a "small, but very important victory." Courtesy of Chris Newman hide caption

itoggle caption Courtesy of Chris Newman

Closing loopholes in background checks for gun purchases would reduce the risk of death and injury, doctors' and attorneys' groups say. Alexa Miller/Getty Images hide caption

itoggle caption Alexa Miller/Getty Images

An overgrowth of Clostridium difficile bacteria can inflame the colon with a life-threatening infection. Dr. David Phillips/Getty Images/Visuals Unlimited hide caption

itoggle caption Dr. David Phillips/Getty Images/Visuals Unlimited

In a landmark new study, researchers found that babies who consumed the equivalent of about 4 heaping teaspoons of peanut butter each week, starting when they were between 4 and 11 months old, were about 80 percent less likely to develop a peanut allergy by age 5. To avoid a choking hazard, doctors say kids should be fed peanuts mixed in other foods, not peanuts or globs of peanut butter. Anna/Flickr hide caption

itoggle caption Anna/Flickr