Biological effects of radiation and their consequences depends strongly on the level of dose rate obtained. Dose rate is a measure of radiation dose intensity (or strength). Low-level doses are common for everyday life. In the following points there are a few examples of radiation exposure, which can be obtained from various sources.
- 05 µSv – Sleeping next to someone
- 09 µSv – Living within 30 miles of a nuclear power plant for a year
- 1 µSv – Eating one banana
- 3 µSv – Living within 50 miles of a coal power plant for a year
- 10 µSv – Average daily dose received from natural background
- 20 µSv – Chest X-ray
From biological consequences point of view, it is very important to distinguish between doses received over short and extended periods. Therefore, biological effects of radiation are typically divided into two categories.
- Acute Doses. An “acute dose” (short-term high-level dose) is one that occurs over a short and finite period of time, i.e., within a day.
- Chronic Doses. A “chronic dose” (long-term low-level dose) is a dose that continues for an extended period of time, i.e., weeks and months, so that it is better described by a dose rate.
High doses tend to kill cells, while low doses tend to damage or change them. High doses can cause visually dramatic radiation burns, and/or rapid fatality through acute radiation syndrome. Acute doses below 250 mGy are unlikely to have any observable effects. Acute doses of about 3 to 5 Gy have a 50% chance of killing a person some weeks after the exposure, if a person receives no medical treatment.
Low doses spread out over long periods of time don’t cause an immediate problem to any body organ. The effects of low doses of radiation occur at the level of the cell, and the results may not be observed for many years. Moreover, some studies demonstrate, most of human tissues exhibit a more pronounced tolerance to the effects of low-LET radiation in case of a prolonged exposure compared to a one-time exposure to a similar dose.