Determination of 40K, 232Th and 238U activity concentrations in ambient PM2.5 aerosols and the associated inhalation effective dose to the public in Jeddah City, Saudi Arabia

• High airborne PM2.5 concentrations over 4 months (24 samples) were found in Jeddah.
• The mean activity concentrations of 40K, 232Th and 238U were assessed in PM2.5.
• Effective inhalation dose due to 40K, 232Th and 238U was 59 nSv/year for adults.
• Effective inhalation dose was higher than the world reference values in air.
• Studying the inhalation dose due to other radioisotopes in PM2.5 is recommended.

Natural radioactivity of soil samples has been studied in many countries of the Arabian Peninsula, including Saudi Arabia. Radiological indices based on soil radioactivity have been widely used in these studies. However, there are no available data about natural radioactivity of fine aerosol particles in such countries. The objective of this study is to determine the activity concentrations of 40K, 232Th and 238U in airborne PM2.5 and the associated internal inhalation radiation dose to the public in Jeddah City, Saudi Arabia. Twenty-four air samples in four locations throughout Jeddah were collected and analyzed for PM2.5 and the associated K, Th and U. The activity concentrations of the isotopes 40K, 232Th and 238U were calculated. High atmospheric PM2.5 concentrations (mean: 50.81 ± 34.02 μg/m3) were found. The natural radioactivity associated with PM2.5 due to the isotopes 40K, 232Th and 238U were 301.8 ± 76.1, 11.8 ± 4.2 and 10.8 ± 3.4 Bq/kg, respectively, and the Raeq was calculated as 44.9 ± 14.0 Bq/kg. The inhalation annual effective radiation dose to the public due to natural isotopes of the airborne PM2.5 was in the range 15.03–58.87 nSv/year, depending on the age group. Although these dose values were associated with the PM2.5 fraction only, they were higher than the world references values in air reported in the UNSCEAR, 2000 report.