The letters did not mention that the milk was a vehicle for radioisotopes. Some doctors defended the M.I.T. researchers who conducted the Fernald experiment, arguing that the school provided an environment where diet could be strictly controlled. But the same control would have been available at any private boarding school near Boston. Perhaps, as one researcher dryly noted, it was unlikely that wealthy children would have volunteered in return for extra milk or a chance to go to the beach. Prisoners at Oregon's state penitentiary had radioactive thymidine injected into their testicles as part of a NASA study to find out if cosmic radiation in space would make astronauts sterile.
Accounts vary as to how many prisoners participated, but it appears to have been about a hundred.
The only voice of protest was raised by the penitentiary chaplain, who forbade Roman Catholic prisoners from volunteering because they would have had to provide masturbated semen samples. The doctor who injected the thymidine avoided discussing cancer with the prisoners. The fate of the Oregon prisoners remains unknown. A follow-up program designed to trace them was rejected by the state of Oregon, which cited a lack of funds. America's radioactive human experiments ended in the early 1970s, but the cloak of secrecy surrounding them wasn't lifted until twenty years later.