![]() intracellulare were considered the most common causes of chronic lung infection worldwide among all the species of NTM. ![]() Human (clinical) disease. By the 1970s, M. At that time, these and other scientists thought that these organisms probably had little or no ability to cause disease (virulence) and that these strains were actually avian tubercle organisms that had lost their ability to cause disease in chickens. avium like organisms in humans were described by other investigators along with four cases that later were identified as M. By 1953 (10 years later), more cases of M. In 1943, one of the first human cases of MAC was described when a mycobacterial species later identified as Mycobacterium avium was recovered from the sputum of a patient suffering from chronic lung disease with an associated underlying lung illness called silicosis (related to silica inhalation). Later studies revealed the organisms to be M. In 1933, human-derived disease causing (pathogenic) strains were reported. Human disease due to MAC was not recognized until almost a half century later. By 1890, it was recognized that this avian bacteria (now known as Mycobacterium avium) was distinct in the laboratory from the human variety of M. The first probable description of MAC came with the finding of “tuberculosis” in chickens (avian) that mimicked disease seen in humans, described in England in 1868. tuberculosis – so called nontuberculous mycobacteria (NTM) – dates back to the late 1880s when Alvarez and Tavil described the organism later known as Mycobacterium smegmatis. The earliest report of growth of mycobacteria other than M. To find your personal annual radiation dose, use the interactive Personal Annual Radiation Dose Calculator or this printer friendly worksheet.Early history.Robert Koch’s discovery and laboratory culture of the causative agent of tuberculosis ( Mycobacterium tuberculosis), was announced in 1882, and by the end of the century many other varieties of mycobacteria had been described in animals, birds, and also in the environment as non-disease causing organisms. As explained above, the annual average dose per person from all sources is about 620 mrem. We live in a radioactive world, and radiation has always been all around us as a part of our natural environment. Personal Annual Radiation Dose Calculator (Amounts are shown in picocuries per kilogram.) As a result, the average person receives an average internal dose of about 30 millirem of these materials per year from the food and water that we eat and drink, as illustrated by the following table. In addition, all water on Earth contains small amounts of dissolved uranium and thorium. Radioactivity in Food All organic matter (both plant and animal) contains some small amount of radiation from radioactive potassium-40 ( 40K), radium-226 ( 226Ra), and other isotopes. In fact, among these procedures, the NRC and its Agreement States only license and regulate the possession and use of radioactive materials for nuclear medicine. ![]() Instead, most of these procedures are regulated by State health agencies. However, they do not involve radioactive material and, hence, are not regulated by the U.S. For example, a chest x-ray typically gives a dose of about 0.01 rem (10 millirem) and a full-body CT gives a dose of 1 rem (1,000 mrem), as shown in the table to the left.Īmong these medical procedures, x-rays, mammography, and CT use radiation or perform functions similar to those of radioisotopes. Medical procedures account for nearly all (96%) human exposure to man-made radiation. Personal Annual Radiation Dose Calculatorĭoses from Medical Procedures Medical Procedure Doses.In general, a yearly dose of 620 millirem from all radiation sources has not been shown to cause humans any harm. (The chart to the right shows these radiation doses in perspective.) The other half (0.31 rem or 310 mrem) comes from man-made sources of radiation, including medical, commercial, and industrial sources. Most of this background exposure comes from radon in the air, with smaller amounts from cosmic rays and the Earth itself. Half of this dose comes from natural background radiation. On average, Americans receive a radiation dose of about 0.62 rem (620 millirem) each year. ![]()
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