Gravitational Effects of a Small Primordial Black Hole Passing Through the Human Body

The gravitational effects of a primordial black hole (PBH) passing through the human body are examined, with the goal of determining the minimum mass necessary to produce significant injury or death. Two effects are examined: the damage caused by a shock wave propagating outward from the black hole trajectory, and the dissociation of brain cells from tidal forces produced by the black hole on its passage through the human body. It is found that the former is the dominant effect, with a cutoff mass for serious injury or death of approximately $M_{PBH} > 1.4 \times 10^{17} {\rm g}$. The number density of primordial black holes with a mass above this cutoff is far too small to produce any observable effects on the human population.