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

https://doi.org/10.1016/j.jenvrad.2014.01.003Get rights and content

Highlights

  • 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.

Abstract

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.

Introduction

Naturally occurring radioisotopes, such as 40K and radionuclides from the 232Th and 238U series and their decay products are the main source of external radiation to the human body (Al-Masri et al., 2006, Tzortzis and Tsertos, 2004, UNSCEAR, 2000). Numerous studies all over the world have been conducted to determine the activity of these radioisotopes in soils and rocks to estimate the external gamma-radiation dose to the public. Data from several countries are presented in the UNSCEAR report (UNSCEAR, 2000). However, this report did not include data from the countries of the Arabian Peninsula.

During the last decade, several studies have been conducted in the countries of the Arabian Peninsula, including Saudi Arabia, to determine the activity concentrations of the naturally occurring radionuclides in soil and rock samples (Al-Kheliewi et al., 2012, Al-Sulaiti et al., 2012, Pietsch and Mabit, 2012, Abdul-Hadi et al., 2011; Al-Trabulsy et al., 2011; Al-Trabulsy et al., 2010, Abusini et al., 2008, Orabi et al., 2006, Saleh, 2003, Al-Kahtani et al., 2001). In most of these studies the external radiation dose was calculated. Internal radiation dose form ingestion (Kadi, 2005, Tayyeb et al., 1998), tobacco (Farid, 2012) and building materials (Alharbi and AlZahrani, 2012) were also studied. However, internal dose due to inhalation of fine aerosol particles in the Arabian Peninsula are not found in the literature although atmospheric aerosol concentrations are expected to be high due to the arid nature of the region and the frequent dust storms from the desert. In addition, it is estimated that more than a half of total radioactive dose rate received by world's population is associated to radioactivity inhalation via aerosol particles (UNSCEAR, 2000).

Fine aerosol particles, particularly PM2.5, are of interest because they have the ability to penetrate deep into the lung and can cause harmful health effects (Aburas et al., 2011, Na and Cocker, 2009, Sloss and Smith, 2000). For instance, The European Environment Agency estimated the average loss of life expectancy in Europe due to atmospheric fine particulate (PM2.5) to be 9 months (Monks et al., 2009).

Radioactivity of aerosol particles depends on their sources. In arid areas, such as Saudi Arabia, natural sources are the main contributor to PM2.5, as revealed by Aburas et al. (2011). Therefore, it is expected that naturally occurring radionuclides are the main contributor to PM2.5 radioactivity in such areas.

The objective of the current study is to determine the activity concentrations of 40K, 232Th and 238U in airborne PM2.5 and the associated internal radiation dose to the public due to inhalation in Jeddah City, Saudi Arabia.

Section snippets

Air sampling locations

Air sampling for PM2.5 was conducted at four sites distributed throughout Jeddah City, as shown in Fig. 1. Site A was located at a residential location (Annahdah District) south west of King Abdulaziz International Airport and near three main roads, namely Hira'a Street, Prince Sultan Street, and King Abdulaziz Street. Site B was located at a mixed residential/commercial area (Alfaysalyah District) and near three main roads, being King Fahad Road, Sari Street, and Almadinah Road. Site C was

Airborne PM2.5 concentration

During the study period, the concentration range of airborne PM2.5 was 16.5–188.4 μg/m3 (mean: 50.81 ± 34.02 μg/m3). Table 3 shows that the differences of PM2.5 concentrations among the four sampling sites were statistically insignificant (P-value = 0.578). The relatively higher average at sampling site D was attributed to very high PM2.5 concentration at one sampling day (188.4 μg/m3) due to a dust storm.

Stationary and mobile anthropogenic sources of airborne dust in Jeddah City are found

Conclusion

High atmospheric PM2.5 concentrations (50.81 ± 34.02 μg/m3) were found in Jeddah City, Saudi Arabia. The natural radioactivity associated with PM2.5 due to the isotopes 40K, 232Th and 238U was assessed. The mean activity concentrations of the three isotopes 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 radionuclides 232Th and 238U were suggested to be originated from crustal enrichment, whereas the isotope 40K might be

Acknowledgment

The authors would like to thank Jeddah Municipality for funding this study.

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