Radiation: Negative Effects it Has on Humans

The most common forms of ionizing radiation are alpha and beta particles, or gamma and X-rays.
What kinds of health effects does exposure to radiation cause?
In general, the amount and duration of radiation exposure affects the severity or type of health effect. There are two broad categories of health effects: stochastic and non-stochastic.

Stochastic Health Effects

Stochastic effects are associated with long-term, low-level (chronic) exposure to radiation. (“Stochastic” refers to the likelihood that something will happen.) Increased levels of exposure make these health effects more likely to occur, but do not influence the type or severity of the effect.

Cancer is considered by most people the primary health effect from radiation exposure. Simply put, cancer is the uncontrolled growth of cells. Ordinarily, natural processes control the rate at which cells grow and replace themselves. They also control the body’s processes for repairing or replacing damaged tissue. Damage occurring at the cellular or molecular level, can disrupt the control processes, permitting the uncontrolled growth of cells cancer This is why ionizing radiation’s ability to break chemical bonds in atoms and molecules makes it such a potent carcinogen.

Other stochastic effects also occur. Radiation can cause changes in DNA, the “blueprints” that ensure cell repair and replacement produces a perfect copy of the original cell. Changes in DNA are called mutations.

Sometimes the body fails to repair these mutations or even creates mutations during repair. The mutations can be teratogenic or genetic. Teratogenic mutations are caused by exposure of the fetus in the uterus and affect only the individual who was exposed. Genetic mutations are passed on to offspring.

Non-Stochastic Health Effects

Non-stochastic effects appear in cases of exposure to high levels of radiation, and become more severe as the exposure increases. Short-term, high-level exposure is referred to as ‘acute’ exposure.

Many non-cancerous health effects of radiation are non-stochastic. Unlike cancer, health effects from ‘acute’ exposure to radiation usually appear quickly. Acute health effects include burns and radiation sickness. Radiation sickness is also called ‘radiation poisoning.’ It can cause premature aging or even death. If the dose is fatal, death usually occurs within two months. The symptoms of radiation sickness include: nausea, weakness, hair loss, skin burns or diminished organ function.

Medical patients receiving radiation treatments often experience acute effects, because they are receiving relatively high “bursts” of radiation during treatment.
Is any amount of radiation safe?
There is no firm basis for setting a “safe” level of exposure above background for stochastic effects. Many sources emit radiation that is well below natural background levels. This makes it extremely difficult to isolate its stochastic effects. In setting limits, EPA makes the conservative (cautious) assumption that any increase in radiation exposure is accompanied by an increased risk of stochastic effects.

Some scientists assert that low levels of radiation are beneficial to health (this idea is known as hormesis).

However, there do appear to be threshold exposures for the various non-stochastic effects. (Please note that the acute affects in the following table are cumulative. For example, a dose that produces damage to bone marrow will have produced changes in blood chemistry and be accompanied by nausea.)

“What is Radiation?” : How Nuclear Works: World Nuclear Association World-nuclear.org

“Three Types of Radioactive Decay” library.thinkquest.org http://bit.ly/1LEkYNb

Thomson Higher Education 2007 apollo.isc.vsc.edu

Nordqvist, Christian “What Are The Effects Of Radiation On Humans? What Is Radiation Poisoning?” medicalnewstoday March 19, 2011

“Chernobyl Accident 1986” Chernobyl, Chenobyl Accident. world-nuclear.org, April 4, 2012