less dangerous Biological Effects of Radiation nonionizing radiation: bumps e – to higher energy levels or heats molecules; ionizing radiation: knocks e – out of molecules; more dangerous -- e.g., , , , x-rays, high-frequency UV

bone marrow, lymph nodes -- sequence of action in living tissue (1)creates H 2 O + (2)H 2 O + + H 2 O H 3 O + + OH neutral free-radical w /unpaired e – ( O–H) : :. The free-radical initiates a number of chemical rxns. that disrupt cell function. -- the tissues most damaged by radiation are the ones with cells that rapidly reproduce: -- low doses over a long time can induce cancer, which is… the uncontrolled reproduction of cells.

Units for Radiation Doses 1 bequerel (Bq) = 1 disintegration/sec 1 Curie (Ci) = 3.7 x disintegrations/sec 1 gray (Gy) = absorbing 1 J/kg of tissue 1 rad = absorbing 1 x 10 –2 J/kg of tissue Since the various types of radiation damage tissue with various degrees of efficiency, each type has its own relative biological effectiveness (RBE). rem = RBE x rad photon or  RBE = 1 n 0 RBE = 10  RBE = 20 “roentgen equivalent – man” “radiation absorbed dose”

Radon -- an  -emitter from the decay of radium in rocks and soil Ra-226  Rn very dense; seeps into basements and is readily inhaled 10% -- estimated to be responsible for ____ of U.S. lung cancer deaths  Po-218 radon formed radon emits  radiation this, too, is an  -emitter