The cockroach insecticide called “Chinese chalk”

You recently mentioned a cockroach insecticide called “Chinese chalk.” However, you didn’t mention what was in it that makes it so toxic that it was banned. I have used this stuff and it works great.

I didn’t say it didn’t work. People I know who’ve used Chinese chalk claim it at least has some value as a repellent, if not an eradicator of roaches. But here comes the part where I try to squirm out of a slight overstatement.

Chinese chalk is a pressed white powder in stick form that’s sold in some Oriental markets. Its active ingredient is deltamethrin, one of the pyrethrin family of pesticides, which are extracted from the leaves of chrysanthemums, according to the county agriculture office. Deltamethrin in powder form, like other pyrethrins, is supposed to be harmless to warm-blooded animals. (On the other hand, according to a scientific description of deltamethrin, if you have an annoying sea bass infestation in your home, you can knock ’em on their butts with a shot of the stuff. It’s toxic to fish.) Anyway, the official reason that Chinese chalk is banned in the U.S. is not directly because of toxicity but because it does not have EPA approval.

The chalk is (illegally) imported from China, and quality control rather than toxicity is the EPA’s main concern. A stick of chalk should contain 75 percent of the active ingredient. The county ag office recently tested a sample and found it to be 95 percent deltamethrin. In the late ’80s a test sample from county ag contained none at all. Zippo. Nada. Sounds like a quality-control problem to me. The recent testing was done in response to the poisoning of a local four-year-old who ingested some of the chalk. It’s also been reported that an adult died from it, though I’ve seen no confirmation. Aside from the variable level of active ingredient, the EPA’s concerned that some other pesticide might be substituted for deltamethrin in some batches since there’s no control over the conditions under which the stuff is made. And I’ll bet the parents of that four-year-old wouldn’t call Chinese chalk “nontoxic.”