Assessment of heavy metals in propolis and soil from the Pelagonia region, Republic of Macedonia

Abstract

In this study, the contents of five representative heavy metals (Cr, Pb, Zn, Cd and Cu) were determined in soil and propolis samples from four locations in southwestern Macedonia using atomic absorption spectrometry. The aim was to pinpoint the key factors that influence the content of heavy metals in propolis and to establish whether there is a connection between the contents of heavy metals in soil and in propolis from the same location. Generally, at all of the locations, the relative concentrations of heavy metals in soil were found to decrease in the following order: Zn>Cr>Cu>Pb>Cd. The highest mean values for concentrations of heavy metals in these soils were found to be: 72.03, 38.28, 26.64, 17.15 and 0.60 mg kg–1 for Zn, Cr, Cu, Pb and Cd, respectively, and they are all below the target values from the new Dutch list. The general trend of the heavy metal contents in propolis from the same four locations, in decreasing order, is: Pb>Cr>Zn>Cu≈Cd. Generally, the propolis samples from the highland locations (Orle and Rapeš) had lower overall contents of heavy metals than the lowland locations (Novaci and Makovo). All of the analyzed propolis samples meet the requirements of the Macedonian legislation and the international organizations for the maximum allowed levels for heavy metals. Attempts were made to find a correlation between the heavy metal contents in soil and propolis. According to our aim, the investigation presented herein offers one step towards a complete picture of ecological safety of the specific areas in the Republic of Macedonia. To do so, it is necessary to perform additional studies and to find appropriate biomonitoring methods. Further studies are needed to complete the picture and to determine the major pathways of incorporation of heavy metals in beehive products.

Keywords

• atomic absorption spectrometry
• biomarker
• heavy metals
• propolis
• soil