They fill the air with insecticide, don't really penetrate to where the critters are and leave many surfaces coated by pesticide residue that can linger for weeks.

By Eli Wolfe

Fair Warning

A new study has found that bug bombs, which are used by millions of Americans to kill insects such as cockroaches, often fail to eradicate those pests and yet expose consumers to potential health risks.

Researchers from North Carolina State University reported last week that their tests on several types of bug bombs showed that they killed, at most, 38 percent of the wild cockroaches in the spaces where they were used.

Previous studies have shown that the aerosol devices — which douse a room with a fine mist of insecticides and are more formally known as total-release foggers – don’t penetrate crevices and cracks where bugs can thrive. The new study revealed an additional problem: bug bombs deposit significant amounts of insecticide where humans are likely to come into contact with it, such as on tabletops, kitchen counters and floors.

When the North Carolina researchers swabbed rooms exposed to bug bombs, they discovered that many surfaces were coated by pesticide residue that lingered for several weeks.

Zachary DeVries, one of the North Carolina researchers, called the results alarming. He said he and his colleagues followed all of the steps specified on the product labels that are supposed to guarantee consumer safety.

“To put people at risk, you have to have some justification for it,” DeVries said. If bug bombs efficiently wiped out cockroaches while exposing humans to small amounts of pesticide, he said, their use might be justifiable. But, he continued, “at the end of this study, there was no positive that came out of it.”

S.C. Johnson & Son, which markets several of the insecticide products used in the North Carolina study, did not respond to a request for comment.

Federal figures indicate that about 50 million Americans used total-release foggers in 2010. Over the last two decades, the U.S. Centers for Disease Control and Prevention found 3,688 cases of consumers who were sickened after accidentally exposing themselves to bug bombs. The CDC also documented several deaths, but most incidents involved non-fatal and temporary symptoms, including coughing, difficulty breathing, vomiting, nausea and abdominal pain.

Still, little is known about the potential long-term effects of exposure to synthetic pyrethroids, the main insecticide agent in bug bombs.