Leafy vegetables are used in various cuisines worldwide; however, as they cannot be peeled and their leaf surface area is large, the risk of retaining pesticide residues on these vegetables is relatively higher than on others. To our knowledge, this is the first comparative study to reveal the effect of removing pesticide residues from five artificially contaminated leafy vegetables (lettuce, perilla leaves, spinach, crown daisy, and ssamchoo (Brassica lee ssp. namai)) using different removal methods. The percent reduction range for each method was 43.7–77.0%, and the reduction range for the five leafy vegetables was 40.6–67.4%. Lettuce had the highest reduction (67.4 ± 7.3%), whereas ssamchoo had the lowest reduction (40.6 ± 12.9%). Spinach and crown daisy showed no significant difference in their reductions. Based on reduction by method, running water (77.0 ± 18.0%) and boiling (59.5 ± 31.2%) led to the highest reduction, whereas detergent (43.7 ± 14.5%) led to the lowest reduction. The reductions of chlorfenapyr, diniconazole, indoxacarb, fludioxonil, pyraclostrobin, and lufenuron in the leafy vegetables were lower with blanching and boiling than with other methods (p < 0.05). These results highlight the importance of thoroughly washing leafy vegetables to lower the intake of pesticide residues before cooking.

Leafy vegetables are widely consumed in South Korea, especially in the form of kimchi and namul (seasoned vegetables) and are used for wrapping meat. Therefore, the management of pesticide residues in leafy vegetables is very important. A total of 17,977 samples (49 leafy vegetables) were mainly collected in the largest production area of leafy vegetables (Gwangju Metropolitan City and Chonnam Province) in South Korea. They were analyzed within the government’s monitoring programs (Gwangju Metropolitan City) of pesticide residues between 2005 and 2019. Pesticide residues were found in 2815 samples (15.7%), and 426 samples (2.4%) from among these exceeded the specified maximum residue limits (MRLs). Samples exceeding the MRLs were mostly detected in spinach, ssamchoo (brassica lee ssp. namai), crown daisy, lettuce, and perilla leaves. Azoxystrobin, dimethomorph, and procymidone were the most frequently detected pesticides. However, procymidone, diniconazole, and lufenuron were found to most frequently exceed the MRLs. The rate of MRLs exceeding has been managed below the average (2.4%) more recently than in the past in this area. Further, leafy vegetables with the most violations of the MRLs in our study in South Korea were not harmful to health by a risk assessment (the range of the hazard index was 0.001–7.6%).

South Korea has a unique food culture. South Koreans enjoy wrapping meat and eating or making kimchi (traditionally fermented Korean food) and eating using raw leafy vegetables, stalk and stem vegetables. Therefore, there is a high chance of being exposed to pesticide residues of vegetables. The objective of this study was to investigate pesticide residues in leafy vegetables, stalk and stem vegetables from South Korea. A total of 8496 samples were mainly collected from Gwangju and Jeonnam area (the largest production region of leafy vegetables, stalk and stem vegetables) in South Korea from 2010 to 2014. A total of 230 pesticides were used for multi-residue analysis of pesticides. Among 8496 samples, 61 different pesticides (1029 times) were detected in 890 samples, of which 118 samples (1.4%) exceeded the Korea maximum residue limits (MRLs). Samples exceeding the MRLs were mostly found in leafy vegetables (brassica lee ssp. namai, leafy lettuce, spinach, perilla leaves, crown daisy, marsh mallow, aster scaber, pimpinella brachycarpa) and Chinese chive. Procymidone, dimethomorph and azoxystrobin were the most frequently found pesticides. A risk assessment of pesticides exceeding the MRLs was evaluated by calculating the estimated daily intake (EDI) and the acceptable daily intake (ADI). The ratio of EDI to ADI was 0.003–30.4%.

A phylogenetic analysis of Orientia tsutsugamushi was performed to elucidate its antigenic diversity in chiggers, small mammals, and patients. Between September 2014 and December 2016, a total of 3,816 chiggers were identified within nine species of four genera in the southwest region of Korea: Leptotrombidium scutellare (49.9%; 1,907/3,816), Leptotrombidium orientale (21.1%; 804/3,816), Leptotrombidium pallidum (12.4%; 474/3,816), Euchoengastia koreaensis (7.2%; 273/3,816), Leptotrombidium palpale (6.7%; 256/3,816), Neotrombicular gardellai (1.3%; 50/3,816), Leptotrombidium zetum (0.8%; 32/3,816), Walchia fragilis (0.5%; 18/3,816), and Neotrombicular japonica (> 0.1%; 2/3,816). Twelve chiggers (11 L. scutellare and one L. palpale) tested positive for O. tsutsugamushi by polymerase chain reaction and, except for 1 chigger (KY266830), were part of the Boryong strain cluster. Of the 413 small mammals that were analyzed for O. tsutsugamushi, Apodemus agrarius was the most common rodent species (89.5%; 370/413), followed by Crocidura lasiura (6.8%; 28/413) and Myodes regulus (3.6%; 15/413). The sequence identity of an O. tsutsugamushi sample obtained from the A. agrarius sample population belonged to the Saitama strain cluster. Furthermore, a phylogenetic analysis in 125 patients revealed four clusters (Boryong cluster: 82.4% [103/125], Karp: 13.6% [17/125], Kawasaki: 3.2% [4/125], and Saitama: 0.8% [1/125]). This study clarified the phylogenetic relationship for O. tsutsugamushi in chiggers, small mammals, and patients. The Boryong strain was the most common strain in chiggers and patients. In addition, various strains were identified, except for the Boryong strain, in the southwest region of Korea. Overall, the data presented here will be helpful for the establishment of prevention strategies for scrub typhus.