As I get older the list of things I didn’t know gets longer, but this topic falls in a totally different category—things I didn’t even suspect. Japanese researchers suggest environmental low-frequency noise may trigger blood vessel damage to kidneys. Laboratory animals were exposed to human-made sounds, such as air conditioners and water pumps. The study found it is not how loud the sound, but the pitch. Surprising to researchers is that kidney dysfunction occurred at pitch levels below the hearing range of the laboratory animals. Previous studies have hinted that humans surrounded by more environmental noise tend to have worse kidney function. This study, in the journal Environmental Science & Technology, points to which part of noise may be harmful.