A rare form of oxygen, ozone is a poisonous, faintly blue gas that is produced by the action of electrical
discharges (such as lightning) on oxygen molecules. Ozone occurs naturally in the upper atmosphere, where it screens the Earth from most of the Sun’s harmful ultraviolet radiation. The ozone layer is being depleted by atmospheric pollutants, allowing increasing amounts of ultraviolet radiation to reach the Earth’s surface. This problem could lead to a rise in the incidence of skin cancer and cataracts, as well as having other potentially hazardous effects.pacemaker A small device that supplies electrical impulses to the heart to maintain a regular heartbeat. A pacemaker is implanted when the sinoatrial node in the heart malfunctions, or when the passage of the electrical impulses that stimulate heart contractions is impaired (see heart block; sick sinus syndrome).
Pacemakers can be fixed-rate (which discharge impulses at a steady rate) or demand (which discharge only when the heart rate slows or a beat is missed). They may be external (used as a temporary measure) or internal (implanted in the chest). Some types can increase the heart rate during exercise or change an abnormal rhythm into a normal one.
A specially active and poisonous form of OXYGEN in which three volumes of the gas are condensed into the space ordinarily occupied by two. It has a characteristic smell and is a strong oxidising agent. Formed when an electrical charge is passed through oxygen or air, it is found at high altitudes in the atmosphere where it screens out much of the sun’s ultraviolet radiation. The ozone layer, as it is called, is being damaged by pollutant gases from earth. Unless this damage is reversed, lethal quantities of ultraviolet radiation could penetrate to the earth’s surface, further warming the world’s climates, with long-term damage to the environment.
n. a poisonous gas containing three oxygen atoms per molecule. Ozone is a very powerful oxidizing agent and is formed when oxygen or air is subjected to electric discharge. Ozone in the troposphere (the atmospheric layer closest to the earth’s surface), as found in photochemical smog, can cause health problems. Ozone at very high altitudes (the ozone layer) is responsible for absorbing a large proportion of the sun’s ultraviolet radiation. Without this absorption by ozone the earth would be subjected to a lethal amount of ultraviolet radiation.
p
Health Encyclopedia