It's the volume

Q. Just how bad for my hearing are earbud headphones?

A. They're no more dangerous than the old-school earmuff kind.

"All headphones have the capacity to damage hearing if a person uses them at high volume for a long time," says Brian Fligor, director of diagnostic audiology at Children's Hospital Boston.

Specifically, a recent Harvard study found that adults who listened to music with headphones for 90 minutes at 80 percent of maximum volume experienced permanent hearing loss. Problem is, it's easy to crank your tunes too loud and for too long when background noise is intruding from your environment, be it the din of the gym or the sounds of the street.

One solution: noise-blocking headphones, such as Shure E4c Sound Isolating Earphones ($320, shure.com). Or, if you'd rather not abandon the buds you already have, see if your MP3 player has a volume-limit function. iPod users can download Apple's volume limiter (apple.com/ipod/download).

Q. Is it healthier to grill with propane or charcoal?

A. Props go to propane. In one study by scientists, charcoal-grilled meats contained more carcinogens called polycyclic aromatic hydrocarbons than meat heated with propane. When fat drips from meat, the fat burns and creates PAH-infused smoke, which coats what you're cooking. And charcoal makes more smoke than gas does.

Also, charcoal flames are hotter, which chars meat and creates heterocyclic amines, another carcinogen. Propane still produces some PAHs and HCAs, though, so take these steps with any grill:

Trim fat. Lean meats create less drippings and less smoke, which reduces PAHs.

Marinate. Soaking meat in vinegar or lemon juice reduces HCAs by 90 percent.

Flip frequently. Studies have shown that turning meat frequently results in fewer HCAs.