## 3 Results and Discussion
### Effect of Peeling on the Content of Pesticides
Among 240 analysed samples, 207 samples contained residues of plant protection agents such as imazalli, thiabendazole and prochloraz, in 70%, 36% and 11% of the samples, respectively. In addition, those authors observed notable levels of chlorpyrifos, hexythiazox, methidathion and tebufenpyrad. They also noted considerable concentrations of pesticides in the peels of the analysed fruits. On the basis of an experiment on lemons and oranges, they concluded that fungicides applied after the harvest of the fruits accumulated in 85-90% in the fruit peel. In samples of lemon peels, the presence of fenhexamid was detected, at an average concentration of 30.25 \(\pm\) 18.34 mg/kg and a maximum of 66 mg/kg [78]. Analysis of the specific parts of the fruits of orange and mandarin revealed significant differences in the level of imazalli. In addition, differences in the level of fenhexamid were noted in the analysed parts of lemon fruit samples. In the analysed samples of orange, 6% of imazalli migrated from the peel to the flesh, while in the case of mandarin that value was as low as 1.6%. In the case of samples of mandarins, 16% of carbendazim migrated from the peel to the flesh, and in the case of samples of lemons 25% of fenhexamid penetrated from the peel to the flesh. The relatively low rate of penetration of fungicides to the flesh probably resulted from the physicochemical properties of the analytes under examination and of the peel of the analysed fruit samples. In reality, the levels of both fungicides were considerably higher in the peels than in the whole fruits. In view of the above, and of the lack of knowledge on the origin of the products, it is not recommended to use peels of citrus fruits for the preparation of meals or drinks. In actual life, the peels of citrus fruits are often used in the preparation of liqueurs, jams, or pastry. In a study on oranges, [PERSON] et al. [91] demonstrated a significantly higher content of pesticides in the peels compared to the flesh (7.5-17.9%), with the exception of prochloraz, whose content in the flesh of the fruits was 65.4%. Peeling resulted in a significant reduction in the level of residues of pesticides in the fruit flesh [91]. Impregnation of citrus fruits through immersion in a solution containing fungicides is extensively applied to prevent losses during fruit storage and distribution [81]. That procedure was the cause of residue levels exceeding the MRL demonstrated by the cited authors in the case of chlorpyrifos and imazalli. In the case of imazalli, the highest concentration was ca. 1.1 mg/kg, and in the case of chlorpyrifos ca. 1.6 mg/kg, i.e., considerably higher than in the peels of citrus fruits analysed in this study. Such a situation poses a potential hazard to the consumer, especially when also fruit peels are consumed, e.g., candid peel of lemons, oranges and grapefruits (commonly used in the confectionery industry). Another important aspect is the total content of all pesticides, which can have a synergistic effect on human health, hence the importance of limitation of the use of pesticides. This is reflected in the observed trend, especially in the case of apples, where in 2020 the levels and numbers of identified pesticides were significantly lower compared to the year 2012.