Background radiation includes both natural and artificial sources of ionizing radiation that people are exposed to on Earth. Natural sources, such as cosmic rays and radon gas from rocks, contribute significantly to radiation exposure, while artificial sources include radioactive waste and medical x-rays. Radon gas, produced from uranium decay, accounts for about 50% of natural background radiation and can accumulate in enclosed spaces.

2. Background radiation
• Background radiation is the
present ionizing radiation that people
on the planet Earth are exposed to,
including natural and artificial
sources.

3. Natural Sources
Natural sources of background radiation include:
• Cosmic rays - radiation that reaches the Earth
from space
• Rocks and soil - some rocks are radioactive and
give off radioactive radon gas
• Living things - plants absorb radioactive materials
from the soil and these pass up the food chain
• For most people, natural sources contribute the
most to their background radiation dose.

4. Artificial Radiation
Human activity has added to background radiation by
creating and using artificial sources of radiation.
These include:
 Radioactive waste from nuclear power stations
 Radioactive fallout from nuclear weapons testing
 Medical x-rays.

5. Internal radiation
Internal radiation is background radiation due to
radioactive sources present inside our bodies.
Some of these are from naturally occurring
events. An example is carbon 14 that is formed
in the atmosphere by the Sun’s radiation. This
behaves chemically and biologically in the same
way as non-radioactive carbon 12.

8.  Cosmic rays are a form of natural background
radiation produced by the nuclear reactions occurring
in stars and exploding stars called supernovae.
These produce high energy particles which
continually bombard the Earth.
Our atmosphere gives us good protection from
cosmic radiation

9. Radon gas accounts for about 50% of
natural background radiation.
Radon is a colourless and extremely volatile gas
produced by the decay of uranium U238.
Radon gas occurs naturally, and is constantly produced
by certain rocks in the Earth’s crust.
The main source of Radon gas is the ground: it seeps
through the soil and accumulates into rooms and
enclosed places.