Human subjects for experimentation (in order to acquire knowledge rather than improve the subject's condition) may be coerced into participation or participating unknowingly. Scientific researchers may be able to obtain institutional facilities for research on humans who are not always in a position to give their free consent. Subjects may be ill-informed of potential effects; they may be unable to end their participation once the experiment has begun, even though there is a chance of permanent damage; and they may be unable to receive compensation should they be injured.
Research has been conducted using mentally retarded children, prisoners, or military personnel without adequate regard for the social, moral and ethical implications. Because of the controversial nature of such research methods they tend to be used in an atmosphere of total or semi-secrecy.
Past examples of specific abusive experimentation on humans include experiments on twins, dwarves and pregnant women in Nazi concentration camps; and Unit 731, a Japanese biological warfare centre during World War II, where experiments were carried out on Asian and allied prisoners. Soldiers have been experimental subjects in experiments on atomic bomb testing. Moral codes to be followed when human subjects are used for experimentation have been adopted by the Nuremberg Tribunal, the Helsinki Declaration, and USA, UK and French medical associations.
The American government claims that radioactive medical tests on unknowing subjects (around 1,000) during the Cold War in the USA have for the most part involved little or no risk. There are a number of American experiments which are more dubious, including radiation of prisoner genitals, plutonium or radioactive iodine injection and feeding radioactive material to mentally handicapped people. The tests were all done on people the Atomic Energy Commission considered "disposable": black newborns, prisoners, mental patients, indigents, the terminally ill, and black and pregnant women who were soon to give up their children for adoption.
More than 43,300 American military and industrial sites may have suffered radioactive contamination.
The US government continued experimenting on ill-informed troops and prisoners, as well as unsuspecting civilians, well into the 1970s. In one example, bacteria assumed harmless were released in airports and subways.
In 1993 it was confirmed that Americans were used in radiation experiments in the 1940s without being informed of the health risks. It was claimed that some 800 experiments on 600 individuals were conducted properly. In 1994 evidence surfaced that parental consent forms for radiation experiments run in the 1960's did not mention radiation. Between 1944 and 1961 in the USA there were about 250 experiments involving deliberate release of radioactive materials into the atmosphere. In addition, the American government conducted 204 secret underground nuclear tests between 1963 and 1990, whose potential effects can only be guessed at.
In high nuclear fall-out areas in Utah, childhood leukaemia rates are 2.5 times the American average.