All nuclear power plants release radioactivity in either liquid or gaseous form into the environment on a daily basis. The two reactors at San Onofre release more than 30 radionuclides every day into the atmosphere of Southern California, including highly dangerous Strontium-90 and Caesium-137. Liquid releases into the Pacific Ocean comprise more than 20 radionuclides, including Iodine-131 and Caesium-137.
These are so-called "permissible" levels of contamination under U.S. law, but permissible does not mean safe. The internationally accepted standard is that there is no safe level of radiation exposure – what scientists call a “linear no threshold” standard. Particularly vulnerable are children, infants, and women. Human exposure even to low-level radiation can result in higher risk of damaged tissues, cells, DNA, and other vital molecules – causing programmed cell death (apoptosis), genetic mutations, cancers, leukaemia, birth defects, and reproductive-, immune-, and endocrine-system disorders. In recent years studies have been published that have identified increased risk of leukaemia for children living in proximity to nuclear reactors.
Radiation detectors at most reactors are set to allow contaminated water to be released unfiltered if it does not contain radiation above the "permissible" legal levels. The Nuclear Regulatory Commission relies on self-reporting and computer modelling from reactor operators to track radioactive releases and their projected dispersion. A significant portion of the environmental monitoring data, however, is extrapolated. Basically it’s virtual, not real.
Many of the reactors’ radioactive byproducts continue releasing radioactive particles and rays into the environment for enormously long periods of time – described in terms of "half-lives." The Strontium-90 released from San Onofre, for example, has a half-life of 28 years; Caesium-137 has a half life of 30 years. Other radionuclides released by San Onofre have much longer half lives: Americium-241 is 432 years, and plutonium-239 is 21,400 years. Hazardous radiation is emitted from these radionuclides for at least 10 half lives – for example, plutonium-239 will continue emitting hazardous radiation for 214,000 years.
In addition to the routine releases from San Onofre, the people of Southern California are also exposed to higher levels of radiation when the reactors are shut down for regular refueling and maintenance. To remove the fuel from a reactor, the reactor pressure-vessels must be opened up, which releases large volumes of radioactive gases and vapors into the local environment. These include the noble gases, H-3 (tritium), carbon-14, and iodine-131. People living close to nuclear power stations and downwind from them will be exposed to high doses of radiation during these emission spikes – the estimates range from 20 times to 100 times higher than regular radiation release.
In 2012, the National Academy of Sciences announced that the population around San Onofre would be included in a cancer study of populations surrounding nuclear facilities. Professor Steven Wing prepared for Friends of the Earth a submission to the proposed study, which concluded that:
The pilot study proposed by the Committee should be modified to recognize the current infeasibility of adequately quantifying individual doses in an epidemiological study. Rather than conduct the pilot at specific nuclear facilities, a pilot study of all facilities in one state should be conducted. Methods for establishing necessary inter-agency agreements, linking multiple record systems, assuring confidentiality of data, and involving relevant stakeholders would be extremely useful for planning a multi-state study. Studies of childhood cancer based on selection of cases and controls from cohorts of births with exposure classification based on distance of birthplace, and possibly residence history, are justified based on several European studies and the lack of any such study in the United States. Such a study is feasible because it could be based entirely on linkage of existing records. A study of approximately eight states would include a majority of the country’s children born near nuclear facilities during time periods when the candidate state cancer registries have adequate quality and completeness. The Committee’s recommendation for this approach provides the best prospects for producing meaningful research that will advance knowledge about the role of nuclear facilities in cancer risks of neighbouring populations.