N-7 The external gamma-ray exposures of Table 4.1 #1 affect all of the tissues of the body. In addition, beta rays (cesiurm-137 and strontium-90) emanate from soil, but have only a limited range in air and very poor penetration into the body; they might affect the body'ssurface in those regions which are closest to or are actually touching the ground. Shoes and clothing provide complete or almost complete protection. External beta-ray dose is considered to be unimportant on the basis of the following. For gamma rays, the Rongelap Island/Eneu Island external-dose ratio is 1.7 (Table 4.1 #1. The beta-ray dose ratio at .007 mm depth (basal cell layer, skin) should be approximately the same. Therefore, by extrapolation from the determinations at Eneu (Shingleton et al, 1987) the Rongelap basal-cell dose would be 46 mrem/y, and at 1 cm depth practically zero (ICRP 51, Table 26). skin is § rem/y (NCRP Since the radiation protection guide for 1987b), the skin dose is a trivial one. 64