Yttrium, Radioactive

Range of Toxicity

A) TOXICITY: UNITS: The basic units of measure of ionizing radiation are the rad and the gray (Gy). One rad equals 0.01 joules of energy deposited per kilogram of tissue. One Gy equals 100 rads or 1 joule per kilogram. One sievert (Sv) is equivalent to 100 rems, where 1 rem is 1 Gy multiplied by a factor that depends on the type of radiation received. For gamma radiation, this factor is 1, so that 1 Sv equals 1 Gy equals 100 rads equals 100 rems. For alpha radiation, the factor is 20, so that 1 rad equals 20 rems (or Sv). The factor is 1 for beta radiation and between 3 and 20 for neutron energy.
B) Acute radiation syndrome is a symptom complex following whole body irradiation (greater than 1 Gy). It varies in nature and severity, depending upon: (a) dose measured in gray (Gy), (b) dose rate (dose of radiation per unit of time), (c) dose distribution, and (d) individual susceptibility. Whole-body radiation doses can be divided into potentially lethal (2 to 10 Gy), sublethal (less than 2 Gy), and supralethal (greater than 10 Gy) doses.
1) HEMATOPOIETIC (BONE MARROW) SYNDROME: Dose (gamma equivalent values): Greater than 0.7 Gy (greater than 70 rads); mild symptoms may develop following doses as low as at 0.3 Gy (30 rads). GASTROINTESTINAL SYNDROME: Dose (gamma equivalent values): Greater than 10 Gy (greater than 1000 rads); some symptoms may develop following doses as low as 6 Gy (600 rads). NEUROVASCULAR/CARDIOVASCULAR SYNDROME: Dose (gamma equivalent values): Greater than 50 Gy (greater than 5000 rads). Some symptoms may develop following doses as low as 20 Gy (2000 rads). CUTANEOUS RADIATION SYNDROME: Presentation of Local Radiation Injury defined by dose received: 3 Gy: Epilation (hair loss) begins 14 to 21 days after exposure. 6 Gy: Erythema that may be transient soon after exposure (primary erythema), may again appear 14 to 21 days following exposure (secondary erythema). It may also occur from time to time. 0 to 15 Gy: Dry desquamation is the response of the germinal epidermal layer that is seen 20 days after exposure. Mitotic activity slows in the basal and parabasal layers, the epidermis thins, and large flakes of skin desquamate. 20 to 50 Gy: Wet desquamation occurs as a partial thickness injury. There is intracellular edema, a coalescence of vesicles forming macroscopic bullae, and fibrin coating a wet dermal surface. Radionecrosis may develop as the dose increases. Greater than 50 Gy: Damage to endothelial cells and fibrinoid necrosis of the vasculature cause radionecrosis and ulceration.
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