A dirty bomb consists of an explosive component mixed with radiological powder or pellets. On detonation of the device, the explosion would cause the radioactive material to disperse into the immediate area. People would be at risk of the radioactive material being inhaled and landing on their skin/clothing. The initial explosion itself could also cause significant harm and damage depending on its’ size.
Individuals exposed may be at risk of Acute Radiation Syndrome (ARS) or may have future health problems due to development of cancers several years to decades later. The radioactive dust and smoke could also spread further away due to wind and weather, having a wider area of effect and disruption.
Radiation particles cannot be seen, smelt, felt, or tasted. A dirty bomb would also likely result in high economic costs and disruption due to the need for decontamination and possible rebuilding of structures.
Radioactive doses in context:
The measuring unit to show the absorbed radiation dose is called a Sievert (Sv). One Sievert is a large quantity and radiation doses usually encountered are expressed in Millisievert (mSv) or Microsievert (µSv) which are one-thousandth or one-millionth of a Sievert. For example, one chest X-ray will give about 0.2 mSv of radiation dose. Every year our average radiation exposure due to all natural sources amounts to about 2.4 mSv .
To put radiation doses in context and what risk they pose: