Radiation is present throughout the universe. Radioactivity, the decay of atoms, can have deleterious effects on our genes when the electrical ions produced by this decay pass through living tissue. People are both exposed by radiation from outer space and to radioactive materials in the Earth itself. Scientists estimate that about eighty-percent of the radiation we’re exposed to comes from natural sources. Therefore, it’s not surprising that outer space contains radiation, such as high-energy particles, high-energy protons, neutrons and mesons from the sun and other galaxies, which could cause harmful breaks in our DNA. The ionizing radiation can generate damage is the nitrogenous base and sugar portions of DNA, as well as double-strand breaks, single-strand breaks and DNA-DNA and DNA-protein cross links. Currently, double strand DNA breaks are thought to be one of the most significant sources of damage caused by radiation.
Like characters in a science fiction movie, we are constantly bombarded by cosmic radiation. About eight-percent of our annual dosage of radiation comes from outer space. Subatomic particles from cosmos mingle with the Earth’s atmosphere to create radiation. The atmosphere protects us from most cosmic radiation, but the higher the altitude, the more radiation you are exposed to. If you live in Denver, you are getting a bit more cosmic radiation than someone who lives in Florida, but the difference is small. The same principle applies to airplane flights. By getting closer to outer space in a plane, you are increasing your cosmic radiation exposure. That being said, astronauts, who frequent the cosmos more regularly then the average person, are especially exposed to these higher levels of radiation.
The most common way to determine radiation exposure is to look at chromosomal damage in blood lymphocytes. In order to study just how much radiation astronauts traveling in outer space were exposed to, a study conducted by Kerry George and others studied the blood sample of five astronauts collected before and after flight. After performing a chromosomal aberration assay it was concluded that the total number of chromosomal exchange (of sister chromatids) and translocations in the blood samples increased after each flight, indicating that space travel has deleterious effects to the genes. Similarly, a study conducted by I. Testard and others, also indicated the genotoxic, or genetically damaging, effects of space travel. Cytogenetic analysis of blood samples from seven astronauts was measured. After two-three weeks in flights, X-ray equivalent doses of radiation were below 20mGy, but after six months, the level of radiation increased to 95-455 mGY. Based on this, it seems the more time astronauts spent in outer space, the more radiation their cells absorbed. However, the long-term effects of space travel are still unclear.
Another aspect of space travel that may increase a person’s sensitivity to radiation is microgravity, otherwise known as the feeling of “weightlessness.” Scientists have been testing to see if microgravity would affect a cell’s radio-sensitivity, or susceptibility to the harmful effect of ionizing radiation. Perhaps the smaller force of gravity could affect how our cells function in outer space. In one study, a crew-member’s blood taken ten days before and fourteen days after flight was exposed to gamma radiation, and the dose response was similar for pre- and post-flight blood samples. When blood samples from one of the astronauts was studied before and after flight after exposure to X-rays, an enhancement in radio-sensitivity was visible.
These findings were confirmed in another study linking microgravity and cell sensitivity to genotoxins. In this study, human lung fibroblasts were exposed to a carcinogen. One set of the lung samples was then placed onto NASA’s Weightless Wonder apparatus, and another set was left on the ground. An in vitro chromosomal aberration assay was performed, where the amount of damaged chromosomes in metaphase were quantified. Data showed that overall more cell damage occurred in space than on earth. The results suggest that the influence of genotoxic agents increases with less gravitational force.
Based on the experiments discussed above, traveling to outer space does not appear to be as smooth sailing as it may seem. Yet, the important question is the amount of exposure we are exposed to down here on earth (sorry astronauts!) Often, we’re concerned about the impact of medical scans, getting X-rays taken at the dentist’s office, and radiation therapy. These procedures account for about fifteen-percent of our exposure to radiation. Lesser sources of concern stem from glow-in-the-dark watch faces, microwave ovens, cell phones and even antique glass.
But how dangerous are these everyday items, really?
We’ve all been told by our parents to keep the cell phones away when not in use. But do they really pose a danger to our health? What about wireless networks in schools, at home, even coffee shops? Radio frequency is the energy used in wireless technology. Radio waves are a form of non-ionizing radiation, and therefore wireless computer networks don’t seem to be a real threat. Some scientists, quoted by the National Cancer Institute, still believe though that cell phones may increase the risk of cancer. When you use your phone, you’re putting the antenna that generates the radio frequency right next to your head; a study published in February 2011 in the Journal of the American Medical Association said such positioning could alter brain activity. The study used a flip phone; smart phones emit even more radiation. But no one knows how truly dangerous the radiation emitted is because cell phones have only been in widespread use since the 1990s, not long enough to see long-term effects. Still, researchers advise the following: Since most radiation is generated while the call is connecting, don’t put it to your ear until the connection is made. Use the speaker feature when possible or use a Bluetooth.
Another common household item that may be a source of radiation, ironically, is a smoke detector. Ionization smoke detectors detect smoke particles through a radionuclide sealed inside them, while photoelectric smoke detectors utilize a light sensor. Many smoke detectors use a combination of both methods. An ionizing smoke detector does not pose a danger to you as long as you don’t take it apart. The detector uses radioactive americium-241 bonded to foil and sealed in a chamber. Americium-241 emits alpha particles and gamma rays. Ionizing smoke detectors work by sounding an alarm when smoke interrupts the flow of alpha particles.
And, if you did not already see this one coming, there is also considerable amounts of radiation in microwave ovens. Microwaves use radio frequency waves to vibrate the molecules of the food and generate heat. The energy is not radioactive and does not alter the food. The danger from microwave radiation comes if the door is not completely sealed. Microwaves will heat your body just like they warm food, so standing near a broken microwave with a faulty door seal can be dangerous. Repeated slamming or simple deterioration due to age can damage door seals. You cannot see or smell radiation leakage, so the Food and Drug Administration advises caution. Do not stand in front of or lean on the oven while it is in use.
Radiation is not a new creation that industrialized humans invented over the last century. It has always been with us and even inside of us. Although certain professions or activities may be a source of greater radiation, it’s important to exercise caution even during minimal radiation exposure.