Lethal dose , radiation

Chinese Herbal Medicines. Many traditional Chinese medicines have been screened for radioprotective activity in experimental animals. In one study of more than a thousand Chinese herbs, a number of agents increased the survival rate of dogs exposed to a lethal dose of y-rays by 30—40%, and some symptoms of radiation injury were ameHorated. These effects are potentially related to stimulation of the hemopoietic and immune systems (130). Extracts of five Chinese dmg plants, as weU as aspirin, effectively protected mice exposed to 7.5—8.0 Gy (750—800 rad) of y-radiation, and increased survival rates by 8—50% (131). Several Chinese traditional medicines, adininistered ip before or after irradiation, protected against Hpid peroxidation in a variety of mouse tissues, including BM, Hver, and spleen, as weU as in mouse Hver microsomal suspensions irradiated in vitro (132). 

Median Lethal Dose (MLD)—Dose of radiation required to kill, within a specified period (usually 30 days), 50% of the individuals in a large group of animals or organisms. Also called the LD50, or LD50/30 if for 30 days.. 

The recovery of vegetation in a tropical rainforest in Puerto Rico — after plants were deliberately subjected to lethal doses of gamma radiation — closely resembled secondary succession after other types of disturbances, such as mechanical stripping and treatment with the Picloram herbicide (Jordan 1969). 

Lethal dose A dose of ionizing radiation sufficient to cause death. Median lethal dose (MLD or LD50) is the dose required to kill within a specified period of time (usually 30 days) half of the individuals in a large group or organisms similarly exposed. The LD50/30 for man is 400 to 500 rads (4-5 Gy). 

Papers describing the destruction by radiation of approximately 150 microorganisms have been published. Since the work was carried out under varying conditions and with a wide range of objectives it is not prudent to draw quantitative comparisons between lethal curves reported by different scientists. In general, under conditions of normal aeration in buffer or saline solutions the mean lethal doses shown in Table VI may be taken as representative. 

Figure 12-3 Synthetic chelate covalently attached to an antibody carries a metal isotope (M) to deliver lethal doses of radiation to tumor cells...

We measure the ability of radiation to cause harm in reins. Lethal doses of radiation begin at 500 rems. A person has about a 50 percent chance of surviving a dose of this magnitude received over a short period of time. During radiation therapy, a patient may receive localized doses in excess of200 rems each day for a period of weeks (Figure 4.8). 

The 1,3-dioxolane ring is found in a major antifungal drug, ketoconazole (123). Ketoconazole is a broad spectrum, orally active antifungal agent and is used to treat a wide variety of superficial or deep fungal infections. Various workers, especially in Russia, have explored the use of simple oxathiolanes as radioprotectants. For example, the survival rate of mice irradiated with lethal doses of X- or -y-rays was 40% when they were pretreated with 2,2-dimethyl-l,3-oxathiolane. Other oxathiolanes were less active. 1,3-Oxathiolane, administered intravenously to dogs 2 or 3 times daily for 2-4 days before chronic irradiation with polonium-210, increased their life expectancy from 9 months to 3-7 years and alleviated radiation sickness. Some blood indicators were also restored to normal. 

Part of the triage process should include an assessment of radiation exposure received. For example, if a patient is vomiting or has diarrhea on arrival, there is a good chance the patient was exposed to a lethal dose of radiation, if the vomiting is due to radiation exposure and not to stress or illness. 

The lethal effects of inhalation exposure to uranium have been investigated in humans in epidemiological studies and in animal studies under controlled conditions. Epidemiological studies indicate that routine exposure of humans (in the worlq)lace and the environment at large) to airborne uranium is not associated with increased mortality. Brief accidental exposures to very high concentrations of uranium hexafluoride have caused fatalities in humans. Laboratory studies in animals indicate that inhalation exposure to certain uranium compounds can be fatal. These deaths are believed to result from renal failure caused by absorbed uranium. The low specific activity of uranium precludes the possibility of absorbing enough uranium to deliver a lethal dose of radiation. 

General. The median lethal dose of radiation that will kill 50 percent of the exposed persons within a period of 60 days, without medical intervention (designated as LD50/60), is approximately 450 cGy. Medically, other figures of interest are the dose that will kill virtually no one, (LD5), and the dose that will kill virtually every one (LD95). Approximations of those doses are within the ranges 200-300 cGy (free in air) and 600-700 cGy (free in air), respectively. 

B. Exposures to very high concentrations of tritium can cause intakes large enough to induce acute radiation symptoms. An accidental exposure leading to a multicurie dose of tritium induced nausea and exhaustion and eventual death of a victim (Conklin 87). Other estimates put the LD 50 at about 10 Ci this corresponds to about 1 mg of pure tritium. (Sublette 97) This is about the mass of a lethal dose of the nerve agent sarin (Sublette 97). 

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