Too much sun, too much noise while driving

We delved into common driving ailments a few weeks ago, with eye strain and backaches heading the list. For this installment, we ask whether you can get too much sun while driving, and whether blasting a car stereo is bad for your hearing.

It burns

Dr. Paul Lizzul, associate director of clinical research in dermatology at Tufts Medical Center, wasn’t surprised by my sunburn story. Turns out you can get too much sun while driving regardless of whether you have a sunroof.

“If you speak with any dermatologist, there’s going to be a consensus about a higher frequency of skin cancers or sun damage on the left side of someone’s face or arms just because there’s more sun exposure on that side when driving,’’ Lizzul said.

Personally, I like to hang my left elbow out the window, so I’m certainly getting more sun on that side of my body. But what are people supposed to do, put on sunscreen just to go driving?

The more Lizzul spoke, the less crazy that began to sound.

Car windows - and those in your home - are good at filtering out ultraviolet B rays, which cause sunburns. But car and home windows generally don’t filter out ultraviolet A rays, which penetrate deeper into the skin. Ultraviolet A rays, or UVA rays, suppress the immune system and can interfere with your body’s ability to protect against skin cancer, Lizzul said.

“It’s actually the UVA rays that lead to the signs of premature aging and cause wrinkling and sun spots,’’ he said.

Even when I have my car’s sunroof closed, UVA rays are penetrating the glass and pouring onto my head. I’m getting hit when it’s cloudy out, too, Lizzul told me, as up to 80 percent of the sun’s rays can pass through clouds.

The American Academy of Dermatology’s website - www.aad.org - says we should all be wearing sunscreen on exposed areas whenever we go outside. Lizzul recommends applying an ounce of sunscreen - “about the amount of a shot glass’’ - to your hands, arms, and face each morning, and reapplying every two to three hours, regardless of whether you’re going to the beach or just going to work.

He said sunscreens with a sun protection factor (SPF) of at least 30 are sufficient, as they protect against approximately 97 percent of ultraviolet rays. But you can always go higher. Make sure, however, that the sunscreen you buy protects against both UVA and UVB rays.

In some ways, sunscreen is more important for men, Lizzul said, because women’s cosmetic products often contain some form of sun protection, and . . . men go bald. But everyone can benefit by wearing clothing that protects against ultraviolet rays, or donning wide-brimmed hats.

Especially, he said, if you have a car sunroof.

“I often tell my patients you pay the piper for all your youthful indiscretions over the years,’’ Lizzul said. “But that’s not to say you can’t correct the problem now. There’s always more damage that will continue to happen, so if you change your ways you’ll be ahead of the curve.’’

85 decibels

Back in high school, my friend Elmer spent his entire summer’s earnings on a souped-up sound system for his car, the kind you can hear a block away. (Man, was he cool.) Since then, though, I’ve wondered: Can a loud car stereo hurt your hearing?

Possibly, answered Dr. Josef Shargorodsky, an otolaryngologist at the Massachusetts Eye and Ear Infirmary. But only under specific conditions, he said.

The human ear can normally handle noise levels up to 85 decibels for eight continuous hours. When you listen to your car stereo at medium volume with your windows up, the noise level is about 70 decibels. So no problem there. (You can easily check with any number of smartphone apps, such as Sound Meter or Ultimate Ears SPL.)

Your car stereo is naturally harder to hear when your windows are down. So what do you do? You crank it up, probably into the 90- or 95-decibel range, Shargorodsky said.

Your ears can still handle that much noise, though, so long as you’re not driving for more than a couple of hours.

“We usually recommend less than 8 hours for 85 decibels. The rule is if you go louder, every time you increase by 5 decibels, divide the hours by two,’’ Shargorodsky said.

The length of time you’re exposed to loud noise really is the key. You can’t hurt your hearing driving past a jackhammer at a construction site, as loud as that is, because your exposure is so brief. Or by having your windows open while passing through a tunnel, where noise is amplified.

Motorcycle riders should protect their ears if they’re going to be riding for long stretches, as the sound of wind blowing through a helmet can top 85 decibels. “But if you’re just biking to work for half an hour, most likely you’ll be fine,’’ Shargorodsky said.

Under what circumstances could you hurt your hearing?

To hear a car stereo while in a convertible, you’d probably have to crank it above 100 decibels to outdo highway noise. At that level you could suffer hearing loss after just an hour of driving, Shargorodsky said. More likely, though, you’d accrue permanent damage over a longer period.

Ringing in the ears is usually the first sign of trouble in any situation. Fortunately, if addressed quickly, it’s usually temporary, Shargorodsky said.

“You don’t have to put cotton in your ears. Just give it some time,’’ he said. “If you close the windows and turn the radio down you should sufficiently get the levels OK.’’

Was my high school friend foolish to buy such a fancy car stereo?

“Everything varies,’’ Shargorodsky said. “You can actually get positive effects if you have a system that provides more clarity. With headphones, you can get ones that are more clear than others, so you can actually turn the sound down. Same thing with car stereos.’’

I’m not sure that’s why any teenager invests in stereo equipment. But as an adult, lowering the volume sure sounds great.

Peter DeMarco lives in Somerville and can be reached at demarco@globe.com. He also updates a Facebook page, “WhotaughtYOUtodrive?’’