"AS ONE WHO SUPPORTED the nuclear arms buildup during the Cold war—which in part contributed to the environment that allowed these experiments to occur—I was nonetheless shocked, surprised and saddened when I found out late last year of the extent of these radiation experiments. It is unconceivable to me that even at the height of the "Communist Threat," our scientists, doctors, military, and, perhaps, political leaders approved some of these experiments to be conducted on an unwitting public."
— Senator John Glenn (the former astronaut) commenting at the onset of the Congressional Human Radiation Experiments Advisory Committee in 1994.
The affinity of fission byproducts to accumulate in living tissues and organs such as the thyroid and the knowledge that radioactive exposure could lead to cancer was publicly known by 1946. Manhattan Engineer District research studies confirmed the lethal effects plutonium inhalation and how injections of plutonium, radium, strontium-90, and other radioisotopes produced bone tumors and other carcinogenic effects. The female reproductive system was shown to be particularly vulnerable to radiation and in 1947, hereditary mutations from low-level radiation exposure were first observed in successive generations of fruit flies.
Environmental monitoring began early on at the Hanford Works. Herbert M. Parker, Chief Health Instruments Scientist stated that "animal experience" was needed to evaluate the "metabolism" of plutonium and other fission products and called for extensive monitoring of radioactivity in the reservation and surrounding areas.  Charged with determining the amount of radioactivity accumulating in wildlife and livestock in and around the Hanford Site, Parker ordered covert field monitoring thyroid studies in 1946 that at times involved the clandestine collection of area wild species and privately owned livestock. According to DuPont officials, H.I. personnel and the army conducted the tests "under conditions which avoided the excitement of public curiosity." 
By the 1950s, extensive classified radiobiological studies and experiments were being conducted on the effects of ionizing radiation on living tissues in humans, animals, plants, and aquatic life. A fisheries laboratory was constructed at the 100 F area around the same time the production plants were built and included a hatchery. Later a biology lab was added with one of its main enterprises dedicated to studying the effects of radioiodine in sheep. Researchers fed sheep food containing iodine-131 while other researchers fed strontium-90 to miniature swine and pygmy goats (see banner image above). The thermal and chemical effects of reactor effluent on salmon were also studied. A field research study was conducted to determine the radioactive levels of fish species living in contaminated sections of the Columbia. Many other animals, including pigs and stray dogs were used as test subjects .  Eventually a radiotoxicology center and ecology group was formed in the 1960s from these areas of research, known as the Pacific Northwest Laboratory.
Environmental studies involving the public, such as those involving the monitoring of farm animals were carried out as classified affairs. In their quest to maintain secrecy, Hanford officials went to great lengths to keep the public unaware of potential or realized radioactive environmental hazards. An early biologist recalled to historian Newell Stannard, "Hanford researchers resorted to deception simply to collect information about possible iodine contamination in livestock, by having employees pretend to be agricultural inspectors while surreptitiously monitoring iodine levels in animal thyroids." He went on to comment, "I was to simulate an animal husbandry specialist who had the responsibility of testing a new portable instrument...that would test the "health and vigor" of animals." Because farmers were often skeptical during the "test," the inspector commented that he was often "successful in placing the instrument over the (animal's) thyroid...when the owner's attention was focused on next animal or some concocted distraction." 
With known radioactive dangers remediation therapies were sought and studies were initiated to determine radiation tolerance levels. Research experimentation involving human subjects tested the effects of tritium, iodine-131, zinc-65, strontium-85, phosphorus-32, iron-59, promethium, and both technetium-95, and 96 on the human body.  Research subjects were Hanford employees— often times the researchers themselves. In 1951, General Electric scientists exposed twelve subjects with tritium oxide to observe percutaneous (through the skin) absorption of the radionuclide. One of the subjects also received atmospheric whole-body tritium exposure. Results from this test caused researchers to recommend a fifty percent reduction in the permissible maximum level for atmospheric tritium oxide.
Two 1963 studies involved radioiodine; in the first, eight GE/Hanford scientists volunteered to consume milk over a one-month period from dairy cows fed iodine-131. The resulting uptake in the human thyroid was monitored at Hanford's whole body counter facility. The second test involved the release of 120 microcuries of iodine-131 into the environment. Two volunteer subjects positioned in the path of the radiation cloud intentionally inhaled the released radioiodine. "The purpose of the experiment was to enable scientists to determine the fraction inhaled by men, the amount taken up by the thyroid and the retention half-time of radioiodine in the human thyroid." 
By far the most famous classified experiment in Hanford's history is the Green Run of 1949 where nearly 8,000 curies of iodine-131 and 20,000 xenon-133 were intentionally released from a separations plant stack. In comparison the March 1979 Three Mile Island accident released between 15 and 24 curies of radioactive iodine. It is speculated that Hanford officials and the military were attempting to simulate the production capabilities of one of Soviet Union's secret plutonium processing plants.
Other research studies funded solely by the Atomic Energy Commission involved 131 prison inmates from 1963 to 1973 from both Washington and Oregon prisons.  Inmates volunteered to be subjects for testicular irradiations to study the effects on ionizing radiation on the male reproductive system, especially the production of sperm cells. The studies directed by Carl G. Heller, M.D. and his assistant, C. Alvin Paulsen, M.D. were controversial as they served no real therapeutic purpose for the inmates. The research was meant to provide research for the nation's high priority nuclear and space programs.
Incarcerated individuals are not in the best position to volunteer for experimental medical studies. The only incentive for the Washington and Oregon inmates were financial— each test subject was paid $25.00 for each testicular biopsy compared to the typical 25 cents a day for inmates laboring in prison industries.  At some point during the recruitment process doctors required test subjects to agree to a voluntary vasectomy to avoid fathering any genetically damaged children resulting from the procedure. Tested inmates suffered skin burns, pain, orchitis (testicular inflammation), and bleeding from scrotum biopsies. It appears that they were only vaguely informed about the possibility of tumors arising from the procedure but not the possibility of cancer. A series of law suits ensued in 1976 alleging poorly supervised research and lack of informed consent. The suits were settled out of court in 1979 with nine plaintiffs sharing $2,215 in damages.