Smallpox is a disease caused by the Variola major virus. Some experts say that over the centuries it has killed more people than all other infectious diseases combined. Worldwide vaccination stopped the spread of smallpox three decades ago. The last case was reported in 1977. Two research labs still keep small amounts of the
What is radiation?
Radiation is energy. It travels in the form of energy waves or high-speed particles. Radiation can occur naturally or be man-made. There are two types:
Non-ionizing radiation, which includes radio waves, cell phones, microwaves, infrared radiation and visible light
Ionizing radiation, which includes ultraviolet radiation, radon, x-rays, and gamma rays
What are the sources of radiation
Noise is all around you, from televisions and radios to lawn mowers and washing machines. Normally, you hear these sounds at safe levels that don’t affect hearing. But sounds that are too loud or loud sounds over a long time are harmful. They can damage sensitive structures of the inner ear and cause
Lead is a metal that occurs naturally in the earth’s crust. Lead can be found in all parts of our environment. Much of it comes from human activities such as mining and manufacturing. Lead used to be in paint; older houses may still have lead paint. You could be exposed to lead by:
Eating food
Each year, around 48 million people in the United States get sick from contaminated food. Common causes include bacteria and viruses. Less often, the cause may be a parasite or a harmful chemical, such as a high amount of pesticides. Symptoms of foodborne illness depend on the cause. They can be mild or serious. They
We all need to drink water. How much you need depends on your size, activity level, and the weather where you live.
The water you drink is a combination of surface water and groundwater. Surface water includes rivers, lakes and reservoirs. Groundwater comes from underground. The United States has one of the safest water
Asbestos is the name of a group of minerals with long, thin fibers. It was once used widely as insulation. It also occurs in the environment. Asbestos fibers are so small you can’t see them. If you disturb asbestos, the fibers can float in the air. This makes them easy to inhale, and some may