Preliminary assessment of heavy metal contamination in children’s cereal bars: implications for consumer safety on the Polish market

The primary objective of this study is to evaluate the content of heavy metals, including cadmium, lead, zinc, arsenic, copper and nickel, in cereal bars intended for consumption by children and adolescents. The study also aims to identify factors that differentiate the content of these products. The study material comprised 50 cereal bars, which were consumed by a population group of children and adolescents. The determination of zinc, arsenic, copper and nickel was accomplished through the utilisation of optical emission spectrometry with inductively coupled plasma excitation on a spectrometer, while cadmium and lead were ascertained by atomic absorption spectrometry with electrothermal atomization (ET-AAS) on an atomic absorption spectrometer. In the heavy metal analysis of the cereal bars, lead was not detected in contents above the limit of quantification (LOQ) of 0.10 mg/kg. However, three samples exceeded the maximum permissible levels of cadmium, with contents of 0.046 mg/kg in two cases and 0.043 mg/kg in one case, while the minimum determined cadmium content was 0.011 mg/kg. The arsenic content of the samples oscillated between 0.56 and 4.16 mg/kg. Although there are no established standards for nickel, zinc and copper, their contents are of potential health significance in the context of chronic exposure, requiring detailed assessment. The results of the statistical analysis showed significant differences in copper and zinc depending on product composition (p ≤ 0.0001), suggesting higher contents of these metals in oatmeal-dominant products, possibly due to specific raw material sources or variation in the production process. The homogeneity of nickel, cadmium and arsenic contents regardless of product composition was confirmed by the absence of significant statistical differences (p > 0.05). The analysis of geographical variation showed that products of Polish origin were characterised by higher copper and cadmium contents compared to products from Germany, suggesting a potential influence of local environmental and technological conditions. Hazard quotient (HQ and HI) calculations for the analysed scenarios showed that the limits were exceeded, especially for products with a predominance of oatmeal and Polish production, highlighting the need for further research into the sources of these contaminants and their health implications.