Six Harvard University medical researchers were poisoned in August after drinking coffee that was laced with a chemical preservative, according to university officials. The coffee came from a machine near their laboratory that later tested positive for sodium azide, a common preservative used in laboratories. The six reported symptoms after drinking the coffee August 26, ranging from dizziness to ringing in the ears, and one passed out. They were treated at Beth Israel Deaconess Medical Center and later released.