Killing urban rats with dry ice is a cheap, effective, and non-toxic method of pest control, authorities say—but the Environmental Protection Agency wants it to stop. The EPA has informed authorities in cities including New York, Chicago, and Boston that the method is illegal under federal law because it has not been registered with the agency, USA Today reports. Cities have managed to reduce rodent activity by up to 95% with the method, which involves dropping dry ice into rat burrows, covering the exit, and waiting for the frozen carbon dioxide to melt into a gas, suffocating the rats. Officials say the process still needs to be vetted for public safety like any other method of rodent control.
Buddy Christopher, head of Boston's Inspectional Services Department, tells USA Today that the city's dry ice program has been halted but his department has applied for an EPA permit to restart it. "We didn’t see this thing as a pesticide by the classic definition, because dry ice is used everywhere," he says. "You go to a nightclub and they’ll serve cocktails in a bucket of dry ice. This is not necessarily one of those logical things, it's a regulatory issue, and we'll respect everything they want us to do." DNAinfo Chicago reports that PETA has also called for an end to the use of dry ice for rodent control, saying rats "deserve our protection."