More than one billion young people risk damaging their hearing through excessive (过度的) use of smartphones and other audio devices (音频设备), the UN warned Tuesday, proposing new safety standards for safe volume levels.

In order to safeguard hearing, the World Health Organization and International Telecommunications Union issued a voluntary international standard for the manufacture and use of audio devices.

Young people are particularly prone to get risky listening habits. Around half of those between the ages of 12 and 35, or 1.1 billion people, are at risk due to “long exposure to loud sounds, including music they listen to through personal audio devices”, the UN health agency said.

Currently, about five percent of the global population, or some 466 million people, including 34 million children, suffer from disabling hearing loss. WHO considers a volume above 85 decibels (分贝) for eight hours or 100 decibels for 15 minutes as unsafe.

WHO is calling for parental as well as automatic volume controls on audio devices to prevent dangerous use.

While some smartphones and other audio devices already offer some of these features, the UN would like to see a uniform standard used to help protect against disabling hearing loss.

“Think of it like driving on a highway, but without a speedometer (速度计) in your car or a speed limit,” Shelly Chadha of the WHO told reporters in Geneva. “What we’ve proposed is that your smartphones come fitted with a speedometer, with a measurement system which tells you how much sound you’re getting and tells you if you are going over the limit.”

Perhaps you use your headphones to enjoy music and peace and quiet during the day. But you may be neglecting the dangers of hearing loss with headphones. 【小题1】 This is 30% higher than just 20 years before, and experts are pinning it on headphones.

In fact, headphones are not a bad thing. They can bring peace, allow for better musical enjoyment, and even protect your ears from higher decibels(分贝). 【小题2】

How long should you wear your headphones every day? The answer is, according to the World Health Organization, one hour per day. 【小题3】 But the fact is that the longer you listen, you’re going to lose your hearing sooner. To keep hearing loss from happening to you, you should follow the recommendation in place by the WHO that you keep your time with headphones on limited to one hour per day.

Then, how do you set the safest volume for your headphones? With headphones, it depends on the type you’re using and your environment. To test things out, you should take them off your ears and extend them in your hands out in front of you. 【小题4】 If you are using open-back headphones, you should try to have a conversation with someone nearby. When you’re able to carry on the conversation clearly, you’re listening at a proper volume. But do remember that never raise the volume on your listening device over 60% of the maximum!

【小题5】 At others this loss will build up over time. It usually isn’t noticeable in the beginning. It’s not until it’s too late that most people realize that the damage has been done. The only way to know for sure is to consult your doctor.

Bad teeth can be painful and even be deadly. Infections of the gums (牙龈) and teeth can release bacteria into the blood system. Those bacteria can increase the chance of a heart attack or stroke and worsen the effects of other diseases. And adults are not the only ones at risk. For example, a 12­-year-­old   boy died when a tooth infection spread to his brain in 2007 in Washington. Experts said it might have been prevented had he received the dental care he needed.

Experts say good dental care starts at birth. Breast milk，they say，is the best food for the healthy development of teeth. Breast milk can help slow bacterial growth and acid production in the mouth. But dentists say a baby’s gums and early teeth should be cleaned after each feeding by using a cloth with a little warm water. Experts say if you decide to put your baby to sleep with a bottle, give only water.

When baby teeth begin to appear，you can clean them with a wet toothbrush. Dentists say it is important to find soft toothbrushes made especially for babies and to use them very gently. The use of fluoride (氟化物) to protect teeth is common in many parts of the world. For example, it is often added to drinking water supplies. The fluoride mixes with enamel (釉质)，the hard surface on teeth, to help prevent holes from forming.

But young children often swallow toothpaste when they brush their teeth. The American Academy of Pediatric Dentistry notes that swallowing fluoridated toothpaste can cause problems. So young children should be carefully watched when they brush their teeth. And only a small amount of fluoridated toothpaste, the size of a pea, should be used.

Parents often wonder what effect finger sucking might have on their baby’s teeth. Dental experts generally agree that this is fine early in life. Most children stop sucking their fingers by the age of four. If it continues，experts advise parents to talk to their children’s dentists or doctors because it could interfere with the correct development of permanent teeth.

Dentists say children should have their first dental visit at least by the time they are one year old. They say babies should be examined when their first teeth appear—usually at around six months.