ABSTRACT
Vegetation fires release large amounts of smoke particles which carry artificial and natural radionuclides into the atmosphere. Naturally-occurring radionuclides were found to be concentrated from wood to smoke materials by factors of 102–103 on a mass basis. These radionuclides are present in smoke particles (fly ash) from all sizes, from 0.5 μm to >7 μm. Polonium-210, which is the most volatile among all radionuclides analyzed and the most radiotoxic, becomes concentrated especially in the smallest smoke particles, <0.5 μm, which are inhalable. Prolonged breathing in smoked air, as it occurs often during wild forest fires, may give rise to increased inhalation of radionuclides carried by smoke, and polonium-210 alone may originate a radiation dose to the lungs some 2000 times higher than the natural radioactivity background. Altogether natural radionuclides, especially those from uranium and thorium series including polonium-210, may give rise to radiation doses exceeding the dose limit of 1 mSv/year adopted for protection of members of the public. This risk of radiation exposure from smoke makes highly recommended the protection of respiratory tract when breathing in areas affected by forest fires. Although fire fighters generally wear gear to protect the respiratory tract, members of the public often do not and this is likely to having radiological exposure consequences in the population. Recommendations are made to enhance occupational and public safety.
