Everything from hand-sanitizing liquids to products like computer keyboards, shopping carts and tissues tout that they kill 99.9%, or 99.99%, of common bacteria and fungi.
But some of these numbers look like the test scores in a class with a very generous grading curve. They often don’t include all pesky germs, and are based on laboratory tests that don’t represent the imperfections of real-world use. Human subjects, or countertops, in labs are cleaned first, then covered on the surface with a target bug. That is a far cry from a typical kitchen or a pair of grimy hands.
Advertising near-total effectiveness is common; AT&T Wireless’s television ads touting its network coverage of 97% of the U.S. is just the latest example. But it is especially common for health products. Naturally, companies make the claims because they sell products.