Background radiation varies from place to place and over time, depending on the amount of naturally-occurring radioactive elements in soil, water and air. Weather conditions also affect radiation levels, as snow cover may shield these elements, and radioactive particulates can wash out of the air during rain storms.

What is background radiation?

The natural radiation that is always present in the environment. It includes cosmic radiation which comes from the sun and stars, terrestrial radiation which comes from the Earth, and internal radiation which exists in all living things.

What is background radiation count?

The background count rate is measured over a period of 20 minutes because of the random nature of radioactive decay. Dividing by 20 enables the average count rate per minute to be determined. Background count rate is typically 18 counts per minute which does not present a serious health risk to humans.