You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Application of Ultra-Performance Liquid Chromatography/Mass Spectrometry-Based Metabonomic Techniques to Analyze the Joint Toxic Action of Long-Term Low-Level Exposure to a Mixture of Organophosphate Pesticides on Rat Urine Profile. In previously published articles, we evaluated the toxicity of four organophosphate (OP) pesticides (dichlorvos, dimethoate, acephate and phorate) to rats using metabonomic technology at their corresponding no observed adverse effect level (NOAEL). Results show that a single pesticide elicits no toxic response. The present study aimed to determine whether chronic exposure to a mixture of the above four pesticides (at their corresponding NOAEL) can lead to joint toxic action in rats using the same technology. Pesticides were administered daily to rats through drinking water for 24 weeks. The above mixture of the four pesticides showed joint toxic action at the NOAEL of each pesticide. The metabonomic profiles of rats urine were analyzed by ultra-performance liquid chromatography/mass spectrometry. The 16 metabolites statistically significantly changed in all treated groups compared with the control group. Dimethylphosphate and dimethyldithiophosphate exclusively detected in all treated groups can be used as early, sensitive biomarkers for exposure to a mixture of the OP pesticides. Moreover, exposure to the OP pesticides resulted in increased 7-methylguanine, ribothymidine, cholic acid, 4-pyridoxic acid, kynurenine and indoxyl sulfate levels, as well as decreased hippuric acid, creatinine, uric acid, gentisic acid, C18-dihydrosphingosine, phytosphingosine, suberic acid and citric acid. The results indicated that a mixture of OP pesticides induced DNA damage, oxidative stress, disturbed the metabolism of lipids as well as interfered with the tricarboxylic acid cycle. Ensuring food safety requires not only the toxicology test data of each pesticide for the calculation of the acceptable daily intake, but also the joint toxic action.
{"Chemical": ["acephate", "Organophosphate", "indoxyl sulfate", "dimethoate", "gentisic acid", "suberic acid", "phorate", "Dimethylphosphate", "dichlorvos", "dimethyldithiophosphate", "ribothymidine", "tricarboxylic acid", "organophosphate", "phytosphingosine", "uric acid", "kynurenine", "creatinine", "C18-dihydrosphingosine", "citric acid", "4-pyridoxic acid", "cholic acid", "hippuric acid", "7-methylguanine"]}