Lead warning on a gas pump at Keeler's Korner, Lynnwood, Washington. (Joe Mabel) DURHAM, N.C. -- In 1923, lead was first added to gasoline to help keep car engines healthy. However, automotive health came at the great expense of our own well-being. A new study calculates that exposure to car exhaust from leaded gas during childhood stole a collective 824 million IQ points from more than 170 million Americans alive today, about half the population of the United States. The findings, from Aaron Re...