"As the Deepwater Horizon disaster unfolds in the Gulf of Mexico, public health practitioners are having a sinking déjà vu feeling. Once again, environmental disaster has struck, and tens of thousands of emergency responders -- some professionals, but many more volunteers -- have swung into action, potentially risking their health as they work to clean up the worst oil spill in U.S. history. Veterans of similar disasters are wondering if historical lessons learned can help keep the ?damage to a bare minimum. But a paucity of ?hard data on emergency responder health makes it difficult even to ask the right questions."