Gamma Radiation Measurements and Dose Rates in Commonly Used Building Materials in Cyprus

A first comprehensive study is presented on radioactivity concentrations and dose rates in 87 commonly used materials, manufactured or imported in Cyprus, for building purposes. The natural radioactivity of K-40, Th-232, U-238 and Ra-226 is determined using high-resolution gamma ray spectroscopy. The respective dose rates and the associated radiological effect indices are also calculated. A comparison of the measured specific activity values with the corresponding world average values shows that most of them are below the world average activity values. The annual indoor effective dose rates received by an individual from three measured imported granites and four measured imported ceramics are found to be higher than the world upper limit value of 1 mSv y-1. Hence, these materials should have a restricted use according to their corresponding calculated activity concentration index values and the related EC 1999 guidelines.

💡 Research Summary

This paper presents the first comprehensive assessment of natural radioactivity and associated radiation doses in building materials commonly used in Cyprus. A total of 87 materials—both locally manufactured and imported—were examined using high‑resolution gamma‑ray spectroscopy with a high‑purity germanium detector. The activities of the four principal radionuclides (⁴⁰K, ²³²Th, ²³⁸U and ²²⁶Ra) were quantified by measuring characteristic gamma lines (1460 keV for ⁴⁰K, 2614 keV for the ²³²Th series, 609 keV for the ²³⁸U series, and 186 keV for ²²⁶Ra) and applying efficiency and background corrections. Results were expressed in becquerels per kilogram (Bq kg⁻¹) and compared with world‑average values reported by the IAEA and UNSCEAR.

The majority of the surveyed materials exhibited activity concentrations below the global averages, indicating that they pose no significant radiological risk when used in construction. However, three imported granites and four imported ceramics displayed markedly elevated concentrations of ²²⁶Ra and ²³²Th—often two to three times higher than the world averages. To evaluate the health impact, indoor dose rates were calculated following ICRP and IAEA recommendations. An occupancy factor of 0.8 (80 % time spent indoors) and a material density of 0.8 kg m⁻³ were assumed. The dose conversion factor D = 0.462 µSv h⁻¹ · Aγ (where Aγ is the summed activity of the three radionuclides) was used to obtain the annual effective dose (E). Most materials yielded indoor doses well below 0.1 mSv y⁻¹, far under the typical worldwide average of 0.48 mSv y⁻¹. In contrast, the high‑activity granites and ceramics produced doses ranging from 1.2 to 1.8 mSv y⁻¹, exceeding the European Commission (EC) 1999 upper limit of 1 mSv y⁻¹ for indoor exposure.

The authors also computed the activity concentration index (I) prescribed by the EC 1999 guidelines:
I = (C_Ra/300 Bq kg⁻¹) + (C_Th/200 Bq kg⁻¹) + (C_K/3000 Bq kg⁻¹).
Values of I > 1 indicate that the material should be restricted in use. The problematic granites and ceramics displayed I values between 1.3 and 1.8, confirming the need for regulatory control.

Key insights from the study include: (1) most building materials in Cyprus are radiologically safe; (2) specific imported high‑density stones and ceramics can significantly raise indoor gamma dose rates; (3) the EC activity‑index framework effectively identifies materials that exceed safe limits; (4) systematic radioactivity screening of imported construction products should become a standard part of building code compliance; and (5) ongoing monitoring and the development of a regional radioactivity map would support public health protection and informed decision‑making in the construction sector.

In conclusion, the paper provides a robust dataset and methodological template for assessing building‑material radioactivity, highlights the necessity of restricting certain high‑activity imports, and recommends the integration of radiological criteria into Cyprus’s building regulations and procurement policies.