The Effects of Radiation on Animals – Although radium is understood to mean all forms of electromagnetic radiation, including light and radio waves, it is most commonly used to describe ionizing radiation – high energy radiation that can ionize atoms, such as radiation released by the decay of radioactive isotopes. X-rays, gamma rays, and alpha and beta particles are examples of ionizing radiation. If it is present on a significant scale, it may harm the health of humans as well as other animals.
The energy of a photon of electromagnetic relation is given by the Planck-Einstein equation, E = hxv, where E represents the energy, h is the Planck constant and v is the frequency. From this equation, we find that the higher the frequency, the higher the energy.
Gamma rays and X-rays are at the top of the frequency spectrum and therefore have high energy. When a gamma or x-ray photon collides with an electron or a particle, it transfers its energy to the target. This transfer of energy can potentially remove electrons from atoms, or ionize them and break chemical bonds between atoms.
Alpha and beta radiation are particles with a large amount of energy obtained from the decay of unstable isotope nuclei. They have an even greater ability to ionize atoms and disrupt chemical bonds, although they are more easily retained than X-rays and gamma rays. Polonium 210 is an isotope that emits alpha particles. It became news when in 2006 a former Russian KGB agent, Alexander Litvinenko, was poisoned with polonium.
When ionizing radiation hits an animal cell, it breaks the chemical bonds inside the molecules and forms new bonds. The degree of damage the cell undergoes because of these changes will depend on which molecules have been altered and the nature of these changes. Damage to DNA is extremely harmful, as the accumulated changes in cellular DNA can cause cancer.
The cells have an internal repair mechanism and can handle damage to a certain extent. However, if the ionizing radiation reaches an animal cell enough or if the damage is very serious, the cell will die.
The radiation dose is usually measured using a unit called gray or Gy, although another unit – called rad – was preferable until recently, and is still widely used. One rad equals one centigray. The major pains are potentially more lethal to animals. An acute dose of radiation has a rad upwards; chronic exposure consists of repeated exposure to small doses of radiation over a long period of time.
Some animals are more resistant than others. A 2008 episode of the Mythbusters program on the Discovery Channel found that while cockroaches and mealworms are able to withstand higher levels of radiation than humans, these insects will also die from being exposed to massive doses.
Rapidly dividing animal cells suffer the most serious damage upon acute exposure. Bone marrow and lymphoid tissue cells, for example, are vulnerable as rapidly dividing cells in the gastrointestinal lining of mammals. Massive doses of radiation can cause diarrhea, vomiting, internal bleeding, anemia, exhaustion, permanent sterilization, and death.
Exposure to high levels of radiation can also cause permanent damage to the cellular DNA that may eventually cause cancer. The effects obtained in rats are those that were most studied since rats were used in many experiments with radiation.
Ironically, some of the same properties that make ionizing radiation a danger have proven to be beneficial in veterinary medicine. X-rays are a very useful diagnostic method because they can easily penetrate soft tissue and be absorbed by bones that have a higher electron density.
X-rays can help veterinarians find bone fractures and kidney stones and diagnose other disorders. The level used on the X-ray for diagnosis is low enough so that the risks become unconscionable. As in humans, radiation therapy is often used to treat cancer in dogs and cats. Beams of ionizing radiation are emitted into the tumor-seeking to kill the cancerous cells and decrease the size of the tumor. Side effects are usually skin problems that can cause the animal to scratch. Although fatigue and nausea are side effects of radiation therapy in humans, they are not common in dogs and cats.