65 The external gamma-ray exposures of Table 4.1 #1 affect all of In addition, beta rays (cesium-137 and strontium-90) emanate from soil, but have only a limited ra e in air and very poor penetration into the body; they might aff et the body's surface in those regions which are closest to or are ctually touching the ground. Shoes and clothing provide complete o almost complete protection. the tissues of the body. External beta-ray dose is considered to be unimportant basis of the following. For gamma rays, the Rongelap Islan Island external-dose ratio is 1.7 (Table 4.1 #1. The betaratio at .007 mm depth (basal cell layer, skin) should be n the Eneu y dose approximately the same. Therefore, by extrapolation from t ie determinations at Eneu (Shingleton et al, 1987) the Rongelap basal-cell dose would be 46 mrem/y, and at 1 em depth pract cally zero (ICRP 51, Table 26). skin is 5 rem/y (NCRP Since the radiation protection giide for 1987b), the skin dose is a trivial o Ap gege tees gens *: prvanpnmeeenmpmemenspc e.