An explosion at a chemical factory near Seveso, Italy, in 1976 exposed factory workers and local residents to the pollutant dioxin, presenting an opportunity to track how exposure at different ages affects sperm quality.
Now, results from a new study point to a window of vulnerability in reproductive system development when such chemical disruptions may leave a permanent mark. "The timing is very important," says study co-author Larry Needham of the Centers for Disease Control and Prevention (CDC) in Atlanta.
Led by Paolo Mocarelli of the University Milano–Bicocca in Milan, Italy, researchers analyzed levels of dioxin in blood samples taken in 1976 from 135 exposed males. They collected new samples of blood and sperm from these same men, and compared those data to samples from a control group of 184 men.