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All sorts of theories have been proposed to explain the alarming rise -- 6.4 million in 2011, a 42 percent jump from 2004 -- in schoolchildren being diagnosed with Attention-Deficit/Hyperactivity Disorder, or ADHD, requiring therapy, medicine or both to make it through their day. ... Now a new report from the Centers for Disease Control and Prevention brings up another possibility: improper diagnosis. (Cha, 9/3)

The Maryland Department of the Environment says it’s sending out 87,000 letters to landlords who haven’t registered their rental units under a law meant to reduce childhood lead poisoning. (9/4)

People who grow up on farms -- especially dairy farms -- have way fewer allergy and asthma problems than the rest of us. Now one research team thinks they've brought science closer to understanding why. In a study published Thursday in Science, researchers report that they were able to pinpoint one possible mechanism for the allergy protection in mice they studied. Surprisingly, the protein that they fingered as the likely allergy-preventer doesn't actually affect the immune system -- it affects the structural cells that make up the lining of the lung. (Feltman, 9/3)