According to researchers from Cincinnati Children’s Hospital, secondhand smoke may be extremely damaging to children, even in minute amounts. Already known to cause respiratory and behavior problems in kids, smoking has now been linked to lowering a child’s intelligence — affecting reading, math and reasoning skills. In fact, one parent smoking as little as one pack a day may reduce a child’s IQ by as many as two points. Tobacco exposure was determined by measuring levels of cotinine, a marker of tobacco exposure, in the blood of more than 4,000 children ages 6 to 16. As cotinine levels in the children’s blood rose, scores on standardized intelligence and achievement tests fell.