Orders of magnitude (radiation) Orders of magnitude (radiation) Recognized effects of higher acute radiation doses are described in more detail in the article on radiation poisoning. Although the International System of Units (SI) defines the sievert (Sv) as the unit of radiation dose equivalent, chronic radiation levels and standards are still often given in units of millirems (mrem), where 1 mrem equals 1/1000 of a rem and 1 rem equals 0.01 Sv. Light radiation sickness begins at about 50–100 rad (0.5–1 gray (Gy), 0.5–1 Sv, 50–100 rem, 50,000–100,000 mrem). The following table includes some dosages for comparison purposes, using millisieverts (mSv) (one thousandth of
Radiation hormesis "error-prone nonhomologous end joining (NHEJ) repair in postirradiation cellular response, argues strongly against a DNA repair-mediated low-dose threshold for cancer initiation". Recent research observed that DSBs caused by CAT scans are repaired within 24-hours and DSBs maybe more efficiently repaired at low doses, suggesting the risk ionizing radiation at low doses may not by directly proportional to the dose. However, it is not known if low dose ionizing radiation stimulates the repair of DSBs not caused by ionizing radiation "i.e." a hormetic response. Radon gas in homes is the largest source of radiation dose for most individuals and it is