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We are constantly exposed to a wide range of electromagnetic radiation. This can include very low-frequency radio waves; microwaves; visible light; infra- and ultraviolet radiation; and x-rays, gamma rays and cosmic radiation from the universe. Many sources are modern conveniences like cell-phones, computers and home microwave ovens and televisions. Do these types of exposure affect our health? There is not complete consensus among scientists, but here is some of what we do know.
Ionizing and Non-Ionizing Radiation
Ionizing radiation comes from sources that are known to cause DNA damage and have an observed correlation with the development of cancer and birth defects. High-powered, unshielded X-rays are an example. Medical procedures, including CT scans, utilize X-ray but with limited power ranges. Even though low doses are used, shielding is used to limit body exposure of both the patient and medical personnel. Although there has been no research showing an association of medical procedures involving X-rays and very low-dose radioactive dyes with cancer and birth defects, caution is still followed when the patient may be pregnant.
Another form of ionizing radiation found in our environment is gamma radiation. This comes from high-dose radiation in the air and water from nuclear power plants that have been damaged or leaking. This is strongly correlated with the development of a wide variety of cancers and birth defects. Gamma rays can also originate from naturally occurring uranium and from space.
Non-ionizing radiation is our predominant environmental exposure. This type of radiation does not cause DNA damage, but does cause molecular changes to human tissue. Sources include house current, radio waves (as with the use of cell phones), microwave (from transmission towers and home microwave units) and sunlight with its infra- and ultraviolet components.
The health effects of non-ionizing radiation are the most controversial in the medical literature. The following are some of the most common questions posed to physicians and other public health officials:
Are microwave ovens safe?
Microwave ovens work by producing high-frequency radio waves that activate water molecules contained within foods, producing heat. Penetration of the food by the microwave radiation depends on the power of the unit, thickness and density of the food. For some foods, the internal heating is not consistent throughout, allowing for some portions to be undercooked. This is the reason that it is recommended to let the microwave-heated food sit for several minutes to allow for distribution of heat. The basic molecular structure of the food is not changed and is the same as if the food were heated in a conventional oven.
Microwave ovens are shielded, and are safe as long as the door seal is intact. Seals that are broken allow the microwave radiation to leak out. We are also aware of the danger of containers melting or cracking or getting burnt by superheated water.
Can cell-phones cause brain cancer?
The use of hand-held wireless telephones has become part of our daily life. The phone uses built-in small antennae that do produce a small amount of radiofrequency (RF) radiation when the phone is activated. The fact that the phone is held close to face has caused many to be concerned on whether this radiation can lead to head or brain tumors.
This is an unanswered question that has prompted ongoing monitoring by the Federal Drug Administration (FDA) and World Health Organization (WHO). The key to the safe use of this technology is to limit the length of calls and to use Bluetooth wireless technology earphones that eliminate the need for the phone to be held close to the head. Currently the FDA continues to monitor this and states that risk is “probably small”.
What about power lines?
The potential health problems from radio-wave radiation and electromagnetic fields from overhead power lines have been the source of much controversy over the years. Many claims have been made that proximity to power lines can lead to childhood leukemia, depression, central nervous system symptoms, breast and skin cancer. Studies by the National Academy of Sciences and National Cancer Institute have not found any links to cancer. However, there have been fewer studies carried out that look at other symptoms such as fatigue, headaches, depression, etc. Again, this is an ongoing issue.
Are microwave antenna towers a health threat?
This topic comes up when radio antennas and microwave towers are proposed close to schools or homes. The Federal Communications Commission has regulatory standards that govern the location of towers and the levels of radiofrequency radiation allowed around these structures. For the most part, radio antennas are usually grouped together in a commercial area and located on higher elevations and not close to homes or schools. The same applies for communication microwave transmitters. Generally, these transmitters are located on elevated roofs or poles/antennas and produce minimal exposure at ground level.