A medical college in San Francisco has offered its apologies more than 50 years after allowing its researchers to conduct dozens of unethical medical experiments on California inmates. The work of two dermatologists at the University of California, San Francisco between 1960 and 1980 was thrust back into the spotlight this month after the publication of a report by the school’s Program for Historical Reconciliation, which found no evidence that Dr. Howard Maibach and Dr. William Epstein had obtained informed consent from the more than 2,600 incarcerated men they experimented on. Their research involved putting the inmates, who volunteered and were paid $30 a month for the studies, in contact with pesticides and herbicides—sometimes by placing it on their skin or injecting it into their veins. In a statement, UCSF’s executive vice chancellor and provost said the school apologized “for its explicit role in the harm caused to the subjects, their families and our community by facilitating this research.” While Epstein died in 2006, Maibach, now 93, still practices at the university’s dermatology clinic. His son told the Associated Press in a Thursday email that Maibach had recently suffered a stroke and was unable to comment on the matter.