The biological effects of radiation and their consequences depend strongly on the level of dose rate obtained. Dose rate is a measure of radiation dose intensity (or strength). Low-level doses are common in everyday life. In the following points, a few examples of radiation exposure 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, the biological effects of radiation are typically divided into two categories.
- Acute Doses. An “acute dose” (short-term high-level dose) occurs over a short and finite period, i.e., within a day.
- Chronic Doses. A “chronic dose” (long-term low-level dose) is a dose that continues for an extended period, i.e., weeks and months, so that a dose rate better describes it.
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 don’t cause an immediate problem to any body organ. The effects of low radiation doses occur at the cell level, and the results may not be observed for many years. Moreover, some studies demonstrate that most 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.