The F.D.A. proposed new rules on laws to prevent food contamination in produce and prepared foods on Friday. The New York Times reports on the changes, which include requirements for better record keeping, contingency plans for handling outbreaks, and measures that would prevent the spread of contaminants. For example, new safety measures may include requiring that farm workers wash their hands, install portable toilets in fields and ensuring that foods are cooked at temperatures high enough to kill bacteria.