Heavy metals in honey collected from contaminated locations: a case of Lithuania

Abstract

Honey, as a bioindicator, can be used to determine the level of pollution in the environment with selected pollutants, including heavy metals. Twelve locations were selected for experimental studies near the main sources of pollution: industrial sites, landfills, railways, and highways. The honey samples were burned to ash, and the heavy metals in ashes were determined using aqua regia digestion in the microwave digestion system. The concentration of heavy metals (Cd, Cr, Cu, Pb, and Ni) was determined using a Buck Scientific model 210 VGP atomic absorption spectrophotometer with a graphite furnace atomizer and an acetylene-air flame. These median amounts of heavy metals were found in the analyzed honey samples: 0.0030 mg/kg for Cd, 0.0179 mg/kg for Pb, 0.0317 mg/kg for Cr, 0.0999 mg/kg for Cu, and 0.0332 mg/kg for Ni. The obtained results were compared with honey samples research conducted in other countries. It is difficult to compare the level of heavy metal results found in honey from different countries, as the type of honey, soil composition, rainfall, air temperature, the plants from which it was harvested, its vegetation and flowering duration, and the degree of anthropogenic pollution in the area differ. The heavy metal content tested in honey was found to be low, except for the Pb content in one sample of honey, and did not pose a risk to human health. A statistical analysis including average, median, standard deviation, confidence intervals, and Spearman coefficients was performed for the evaluation of the relationships between the heavy metal quantities and the determination of the impact of pollution sources (transport and industry). The correlation analysis showed a strong negative correlation coefficient between heavy metals and distance (r = −0.593 to −0.204).