Dark Matter collisions with the Human Body
  We investigate the interactions of Weakly Interacting Massive Particles
(WIMPs) with nuclei in the human body. We are motivated by the fact that WIMPs
are excellent candidates for the dark matter in the Universe. Our estimates use
a 70 kg human and a variety of WIMP masses and cross-sections. The
contributions from individual elements in the body are presented and it is
found that the dominant contribution is from scattering off of oxygen
(hydrogen) nuclei for the spin-independent (spin-dependent) interactions. For
the case of 60 GeV WIMPs, we find that, of the billions of WIMPs passing
through a human body per second, roughly ~10 WIMPs hit one of the nuclei in the
human body in an average year, if the scattering is at the maximum consistent
with current bounds on WIMP interactions. We also study the 10-20 GeV WIMPs
with much larger cross-sections that best fit the DAMA, COGENT, and CRESST data
sets and find much higher rates: in this case as many as $10^5$ WIMPs hit a
nucleus in the human body in an average year, corresponding to almost one a
minute. Though WIMP interactions are a source of radiation in the body, the
annual exposure is negligible compared to that from other natural sources
(including radon and cosmic rays), and the WIMP collisions are harmless to
humans.
