Americans are vulnerable, and more needs to be done by chemical companies, emergency responders, communities, and the federal government, she said.

"Incidents we have investigated at the U.S. Chemical Safety Board have revealed serious gaps in the preparations for major chemical releases by companies, emergency responders, government authorities, and the public," Merritt said. Six major accident investigations by the Chemical Safety Board uncovered flaws in local emergency preparedness and response coordination.

Merritt cited chemical accidents the CSB has investigated that revealed inadequate responses by police and firefighters, who were endangered by lack of equipment and improper procedures. Investigations also revealed instances where company procedures were inadequate to prevent explosions or contain and control fires and toxic releases. In some cases, safety shutdown systems failed.

Other gaps in protection uncovered by CSB investigators include poor community notification, toxic chemical plants with no sirens, unprotected police going door-to-door in hazardous environments, inadequate fire department equipment, and lack of knowledge by neighboring residents on how to respond to the emergencies.

“The overall message is clear: A large-scale instantaneous toxic gas release is quite capable of causing thousands of casualties if the conditions are right and the release occurs near a population center,” she said.