Risk assessment for ingestion of off-season longan stimulated by potassium chlorate

Abstract

Off-season longans in Thailand were stimulated by potassium chlorate (KClO₃). KClO₃ is hazardous chemical and prohibited in food since it might cause harm to human health. This research aimed to observe for chemical effects on longan trees, and analyze the chemical residues in longan fruits including ClO₃^-, Cl^-, K⁺ and N⁺, and perform risk assessment for health effects from ingestion. Forty-two longan trees (Dimocarpus longan Lour.) were separated into 8 study groups (n=5) and a control group (n=2). Four dosages of KClO₃ were used according to trees’ bush size, from 25 g/m to 127 g/m. Each dose was for 2 groups, 1 group stimulation via roots and 1 group stimulation via leaves. After application, longan trees were observed for effects on growth, and fruits were collected to analyze for chemical residues at 150, 180 and 210 days. UV-Spectrophotometer was used for ClO₃^- and Cl^- analyses, and Atomic Absorption Spectrophotometer for K⁺ and Na⁺ analyses. Results showed that after KClO₃ application all longan trees had leaves dropped with burned appearance, with lower dose lesser effects and higher dose more effects. Group control grew fruits the earliest and produced bigger fruits than all treated groups at each observation until at fruits-picking time to find that the fruits of group control were the smallest of all. From the growth of longan fruits, we concluded that 43 g/m of KClO₃ should have been the maximum stimulation dose to use for increasing the growth yields for farmer’s benefits, higher dose than this would reduce the benefits, and 25g/m was sufficient for off-season stimulation without significant reduction of yields. Higher KClO₃ doses were found to result in higher ClO₃^-, Cl^-, K⁺, Na⁺ residues in the peel, but accumulation of related chemical residues in the flesh were inconclusive. Application of KClO₃ via roots gave higher accumulation of ClO₃^- and Cl^- residues in the flesh comparing to application via leaves for the same doses. Nevertheless, the study found that stimulation of KClO₃ via roots was a better choice than stimulation via leaves for the same doses when considering for better flesh weights and less adverse effects on plants. The risk assessment for chemical residues found that ingestion of 1,000 g of longan flesh per day was safe since they were all HQ << 1.00, or MOS >> 1.00 for all chemical residues. Therefore, there was no worry for toxicities to concern for general consumers from ingestion of off-season longan flesh within our study settings except for those who had particular underlying health conditions.