Final answer:
People who survive high-level radiation exposure have a higher risk of cancer and genetic defects, with the risk assumed to be cumulative. Low-level radiation may stimulate repair mechanisms, a controversial concept known as hormesis, but most safety guidelines follow the linear hypothesis that any radiation carries risk.
Step-by-step explanation:
It is true that people who survive high-level exposure to radiation are at a much higher risk than the general public of subsequently developing cancer or producing defective offspring. Survivors from events like Hiroshima and Nagasaki and occupational exposures have exhibited increased rates of cancer, such as childhood thyroid cancer following the Chernobyl disaster. While the lifetime risk due to radiation of producing genetic defects is lower compared to cancer deaths, it is not insignificant. Furthermore, the risk for both cancer and genetic defects from radiation are considered to be cumulative with little capacity for self-repair, similar to the risk of skin cancer from UV exposure.
Contrary to the severe risks at high doses, there is a concept known as hormesis, which suggests that at very low levels of radiation, there may be beneficial effects due to the stimulation of repair mechanisms or cellular adaptation. This view is controversial and not universally accepted, with most safety regulations being based on the linear hypothesis, which assumes that all radiation exposure, even at low levels, carries some degree of risk.
Studies on different species have shown varied responses to radiation, indicating that the extrapolation to humans is complex and uncertain. However, based on our biochemical similarity to mice, many scientists believe that humans may also have some natural repair mechanisms that protect against low doses of radiation, though these mechanisms can be overwhelmed at higher exposures.