serious error (re. radiation shielding) in 1975 Summer Study?

,,,and we also need to compare the penetration energy of those particles with the realization that the greater the energy (ev) the fewer the particles involved. Earth gets hit about once a year by protons with an energy of 10^21 ev (a baseball thrown at 30 mph),,,but that's about one particle/year...total rads are directly proportional to the number of particles plus their energy,.