CHARLESTON, W.Va. -- Dangerous levels of the poisonous chemical phosgene may have escaped the DuPont Co. Belle plant and drifted across the Kanawha River as part of a January 2010 leak that killed a DuPont worker, federal investigators revealed Thursday.
U.S. Chemical Safety Board officials used computer models to estimate a "threat zone" from the phosgene leak.
CSB investigators found potentially harmful levels of the chemical -- amounts that could cause serious and irreversible health effects if exposures lasted an hour -- reached at least 0.4 miles from the plant.
Phosgene concentrations on the Kanawha River may have reached the level known as "immediately dangerous to life and health," or the IDLH concentration, the CSB said.
"Lower concentrations could have traveled across the river," the CSB said in a detailed report.
Only two pounds of phosgene were released in the hose leak that killed plant worker Danny Fish, but CSB officials said their computer modeling showed how dangerous the material -- used as a chemical weapon in World War I -- is to plant workers and the public.
"With a very small release of phosgene, there was the potential for an IDLH concentration," said John Bresland, a longtime chemical plant manager and CSB member.
Phosgene is a valuable building block for making other chemicals, and DuPont had used it at Belle to produce various crop protection chemicals. But it is also extremely toxic, and is considered dangerous even in very tiny amounts.
As little as 2 parts per million of phosgene is considered "immediately dangerous to life and health" by the National Institute for Occupational Safety and Health. Phosgene can cause coughing and watery eyes, but can also lead to heart failure and to pulmonary edema, a buildup of fluid in the lungs that can be fatal.
CSB investigators believe that Fish received a lethal dose of phosgene in less than a tenth of a second when he was sprayed in the face and chest from a worn-out chemical hose.
At the time of the incident, DuPont said in a media statement that "there was no off-site exposure or material environmental impact" from the phosgene release or two other incidents that occurred within a 33-hour period at the Belle plant.