Dr. Tom Frieden, director of the CDC, talks with staff from Doctors Without Borders during a visit to the nonprofit group's newest Ebola treatment center in Monrovia, Liberia.
Tommy Trenchard for NPR
A health worker cleans his hands with chlorinated water before entering an Ebola screening tent at the Kenema Government Hospital in Sierra Leone. More than 300 Sierra Leoneans have died of the disease.
Industrial cities like Detroit have high levels of lead in the aging housing stock and in soils. Researchers found that the amount of soil lead in Detroit that gets suspended in the air correlated with the levels of lead in kids' blood.
Spencer Platt/Getty Images