## 3 Results and Discussion
### Pesticide Residues in Apples and Citrus Fruits--Comparison
#### 3.1.1 Apples
The most frequently identified pesticides were: captan (35% of the samples, with mean concentration of 0.171 mg/kg) and boscalid (22% of the samples, with mean concentration of 0.017 mg/kg) [70]. In addition, the authors of the report noted the presence of tebuconazole in 12% of the samples, and fluidoxonil in 9% of the samples [70]. A study on pesticide residues in apples grown in Greece demonstrated that 84% of analysed fruits contained pesticide residues, 55.6% of the analysed samples contained from two to four pesticides, while in 7% of the analysed samples a minimum of four of the analysed compounds were detected [71]. The most frequently detected compound was carbendazim (45.7%), followed by chloryprifos (44.4%). The average detected levels of concentration varied from 0.169 ppm (fluopyram) to 0.005 ppm (triazofos). Furthermore, 19 out of the 40 analysed pesticides were not identified in any of the analysed samples of apples. In several instances, the detected levels of concentration exceeded the relevant MRL values for four pesticides. A monitoring study on apples conducted in Kuwait revealed that 90% of the analysed samples of apples contained a detectable residue of pesticides, with 80% exceeding the MRL values [72]. In five samples of the analysed apples, values above the MRL were noted for imidaloprid, in one sample the excessive concentration related to deltamethrin, and in two samples it related to malathion. Figure 3 presents the frequency of occurrence of pesticides in the analysed samples of apples in the years of the experiment, expressed in the form of percentage share of burdened samples. In 2012, diphenylamine, a growth regulator, was detected in all samples of apples, but the level of the substance did not exceed the MRL. Furthermore, 89% of the samples of apples contained the insecticide disulfoton, and the next most frequently identified compound, at 67%, was the acaricide propagrite, whereas in 2020, fungicides were detected in apple samples: boscalid with frequency of 80%, followed by pyraclostrobin and captan, detected in 60% of the analysed samples. This report also takes into account the long-term hazard, characterised in the form of estimated daily intake of pesticide residues with apples, and indicates that the chronic exposure to captan and boscalid at the average levels observed in the analyses does not pose a threat to any consumer group. The highest estimated daily intake was noted in the case of captan, and it amounted to 213% of the value of the Acceptable Daily Intake (ADI). It was found that, in the case of children, the potential one-time (one day) intake of chloryprifos with a large portion of apples exceeds the value of the Acute Reference Dose (ARfD), which created a potential hazard for consumer health in that individual instance [70]. In Poland, in the period of 2014-2019, the following frequency of pesticide residue occurrence in apples was noted: from the group of fungicides, captan (88%), boscalid (38%), pyraclostrobin (28%), tebuconazole (21%), difeconazole (14%), pirymethananil (12%), fluidoxonil (12%), tofonate methyl (12%), fluopyram (10%), cyprodimil (4%), trifoxystrobin (5%), fluksapryroksad (2%), tetraconazole (2%), bupirymat (1%), izoprirazam (1%), and pentiopyrad (1%); and from the insecticides, acetamipid (58%), methoxyfenzo (30%), indoxacarb (22%), pyrimicarb (13%), chloryprifos methyl (10%), thiazolprid (%), phosmet (5%), flonicamid (4%), and deltamethrin (1%) [17]. More than one pesticide was identified in many samples of analysed apples in Kuwait [72]. Co-occurrence of pesticide residues in a single sample may result from the application of various kinds of pesticides to protect fruits against various pests or diseases. In the cited study, the presence of a single compound was noted in 13 analysed samples of apples (16.25%), while the co-occurrence of two pesticides was identified in two samples (2.5%).