The word “smog” was first used in London during the early 1900s to describe the combination of smoke and fog. Today, the term “smog” is used to describe a mixture of pollutants, primarily made up of ground-level ozone. Ozone can be beneficial or harmful depending on its location. The ozone located high above the surface in the stratosphere protects human health and the environment, but ground-level ozone is responsible for the choking, coughing, and stinging eyes associated with smog.
Smog-forming pollutants come from many sources, such as automobile exhaust, power plants, factories, and many consumer products, including paints, hair spray, charcoal starter fluid, solvents, and even plastic popcorn packaging. In many American cities, at least half of the pollutants come from cars, buses, trucks, and boats. Scientists estimate that about 90 million Americans live in areas with ozone levels above the standards for health safety.
Yes. Washing your hands with soap and water cleans them of pathogens (bacteria and viruses) and chemicals that can cause disease. Hot water is not enough to clean your hands. Using soap adds to the time spent washing and breaks down the grease and dirt that carry most germs.
The most important times to wash your hands with soap and water are after you use the toilet or before handling food. When not washed with soap, hands that have been in contact with human or animal feces, bodily fluids like mucus, and contaminated foods or water can transport bacteria, viruses, and parasites to others. When done thoroughly and at least for 20 seconds, hand washing can prevent all types of illness and disease, skin infections, and eye infections.
Bed-wetting is fairly common and is often just a developmental (age-related) stage. Twenty percent of five-year-olds and 10 percent of six-year-olds wet the bed, according to the American Academy of Pediatrics. And it’s twice as common in boys as it is in girls. Although there are many reasons for wetting the bed at night, doctors say it is often because these children have a difficult time waking up from their deep nighttime sleep.
Some children have a small bladder that is more easily overfilled. Since bedwetting is physical, the child has no control over it when it is happening. However, there are things that you can do to help limit bed-wetting accidents, such as not drinking liquids after dinnertime and using the bathroom right before you go to bed. The majority of children grow out of bed-wetting naturally.
Vitamins are chemicals that the body needs to function well; minerals are metals and salts that the body also needs in tiny amounts to run properly. Both help the human body grow. Different foods, like vegetables, contain different amounts of vitamins and minerals, so it is important to have variety in your diet so you can get a good balance. When it comes to vitamins, each one works differently in your body. Vitamin D in milk helps your bones grow; vitamin A in carrots helps you see at night; vitamin C in oranges helps boost your immune system and helps your body heal if you get a wound; and the B vitamins in leafy green vegetables help your body make protein and energy.
And although some vitamins like A (which helps your eyesight) and D are stored in your body (for several days or up to several months), others, like C and the B vitamins, quickly pass through your bloodstream. So it’s important to replace your vitamins every day.
People with light skin and eyes are more likely to have freckles because they have less melanin, a chemical in the skin that protects it from sun damage by reflecting and absorbing ultraviolet (UV) rays. Instead of tanning, they freckle.
Some people’s freckles fade away almost completely in the winter, and then return in the summer, when the person is more likely to sunburn. Sunscreen can help protect everyone (freckled or not) from the Sun’s harmful rays.
The inability to hear, or deafness, can occur for many reasons. Some types of hearing loss result from something blocking sound as it travels from the outer ear to the eardrum and the tiny bones in the middle ear. Other types of loss arise from damage to or a defect of the inner ear or the auditory nerve, which is the nerve that carries sound signals from the inner ear to the brain. Deafness can happen as a result of disease, including severe ear infections, or it can be inherited, with the deafness being apparent at birth or sometimes showing up years later. Injuries and accidents also account for many cases of deafness.
Extremely loud noises, like those that come from an explosion, can cause deafness, though that loss of hearing is sometimes temporary. People who work in noisy factories or those who are frequently exposed to very loud music can also develop hearing loss over time. Many people gradually lose some or all of their hearing when they reach old age, but some of those types of hearing loss can be overcome by wearing a hearing aid, which makes noises like speech or music louder.
Water is vital to the survival of everything on the planet and is limited in supply. Earth might seem like it has abundant water, but in fact only 1 percent is available for human use. While the population and the demand on freshwater resources are increasing (each person uses about 12,000 gallons of water every year), supply remains the same. Water is constantly being cleaned and recycled through Earth’s water cycle, yet we still need to conserve it because people use up Earth’s freshwater faster than it can naturally be replenished.
When you use water wisely, you help the environment. You save water for fish and animals, help preserve drinking water supplies, and ease the job of wastewater treatment plants—the less water you send down the drain, the less work these plants have to do to make water clean again. When you use water wisely, you also save the energy that your water supplier uses to treat and move water to you, and the energy your family uses to heat your water. Your family pays for the water you use, so if you use less water, you’ll have more money left to spend on other things.
The greenhouse effect describes a warming phenomenon. (In a greenhouse, closed glass windows cause heat to become trapped inside.) The greenhouse effect occurs when a planet’s atmosphere allows heat from the Sun to enter, but refuses to let it leave. A good example of the greenhouse effect can be found on Venus.
There, solar radiation penetrates the atmosphere, reaches the surface, and is reflected back into the atmosphere. The re-radiated heat is trapped by carbon dioxide, which is abundant in Venus’s atmosphere. The result is that Venus has a scorching surface temperature of 900 degrees Fahrenheit (482 degrees Celsius). The greenhouse effect can also be found on Earth and in the upper atmospheres of the giant planets: Jupiter, Saturn, Uranus, and Neptune.
A disability can be the result of a disease, an accident, or of genetics, which means that it is a condition that a person is born with.
A lot of times disabled people can learn new ways to do things or use special machines or specially trained animals to help them work around their disability.
Scientists do not know exactly why people need sleep, but studies show that sleep is necessary for survival. Sleep appears to be necessary for the nervous system to work properly. While too little sleep one night may leave us feeling drowsy and unable to concentrate the next day, a long period of too little sleep leads to poor memory and physical performance.
Hallucinations (seeing things that aren’t really there), vision problems, and mood swings may develop if sleep deprivation continues.