Pesticide poisoning is a global health concern with approximately three million cases being reported on an annual basis. The latter includes both intentional and unintentional poisonings. Organophosphorus and carbamate insecticides are frequently found to be ‘responsible’ for pesticide poisoning in developing countries. In South Africa, aldicarb is the most potent carbamate pesticide and is sold in the informal markets as Temik. It is colloquially known as “Two step” or “Galephirimi” resulting in numerous cases of acute poisoning, especially in urban areas. Underreporting of suspected or confirmed pesticide poisoning cases has been a problem encountered in the national notification systems. Although a number of carbamate poisonings have been identified at the Pretoria Medico-Legal Laboratory, the presence of carbamates in post-mortem samples is rarely confirmed analytically. This may be ascribed to insufficient sample preparation, analytical methods not being sensitive enough or storage conditions not being optimal or too long before analysis takes place. It is well documented that most analytical errors occur during the pre-analytical phase, leading to a high prevalence of inconclusive results being attained. This may possibly be due to pre-analytical degradation, binding to biological matrix or the analytical method not been sensitive enough for detection in collected samples. Post-mortem redistribution factors such as physicochemical properties of the xenobiotic compounds (pH, volume of distribution, protein binding affinity, bacterial biotransformation and lipophilicity), characteristics of the matrix, specimen collection procedure and the use of preservatives may also influence the carbamate stability. The primary aim of the study was to optimise the sample preparation and analysis of biological matrices for select carbamates using LC-MS/MS method. Additionally, to analyse pesticide samples sold by street vendors as well as post-mortem samples collected from suspected cases of carbamate intoxication to determine whether the developed method can detect carbamates in real samples. Assessment of the aldicarb decay kinetics was done by spiking biological samples (whole blood, plasma, urine) collected from consenting healthy volunteers. Post-mortem samples (blood, urine, stomach content) of suspected carbamate poisoning cases, were screened for possible carbamate compounds and their metabolites or breakdown products. Optimisation and validation of the method was performed using a high-performance liquid chromatography (HPLC) system coupled to a triple quadrupole mass spectrometer following different extraction methods. The system was operated in positive electrospray ionisation (ESI+) mode. Different columns, mobile phase buffers and cartridges were used to compare the chromatographic separation of the carbamate compounds. Validation according to ICH guidelines was done for aldicarb. A set of matrix-matched standard calibration curves, was constructed using Analyst (version 1.5.2) software. Initial sample preparation of carbamate pesticides using three different SPE cartridges proved to be unreproducible with poor recoveries of specific compounds due to the wide range of carbamate pesticide polarities, so this was abandoned for the stability testing and forensic samples tested. About 85% reduction of the concentration of aldicarb was seen in whole blood only at ambient temperature but was stable at lower temperatures. Stability proved to be better in plasma compared to whole blood, for aldicarb and its oxidation products. Aldicarb was stable in urine stored with boric acid preservative. The ideal storage temperature for biological samples containing these carbamate compounds was found to be -80°C. During analysis of forensic samples, unknown peaks were consistently detected which are believed to correspond to adulterants and diluents which are added to “backstreet” pesticides. A possible match of an organophosphate, terbufos, found in some “backstreet” pesticide products was detected in some of the post-mortem samples. Considering their different physicochemical properties and that several factors can influence the biodegradation of carbamate compounds, no extrapolation of results from one carbamate compound to another can be formulated. The development and validation of an analytical method to quantify aldicarb and its oxidation products (aldicarb sulfoxide and sulfone) in whole blood, plasma and urine, using the protein precipitation method and LC-MS/MS was successful. Method validation to quantify ten standard carbamate pesticides using SPE and UPLC-q-TOF/MS was unsuccessful. The LC-MS/MS technique was found to be a suitable tool for the quantitation of aldicarb and its oxidation products in typical post-mortem sample matrices. / Dissertation (MSc (Medical Criminalistics))--University of Pretoria, 2021. / Faculty of Health Sciences Research Committee / Department of Pharmacology / University of Pretoria Masters research and research award grant / Forensic Medicine / MSc (Medical Criminalistics) / Unrestricted

Field research was undertaken in three Jamaican farming communities to understand the localized health impact of pesticide poisoning in a developing country. The primary research tool was the collection of data through an intra-household survey, complemented by field observations. The goal was to gather information on the extent to which pesticides are used, the physiological symptoms experienced during or after pesticide exposure, and the farmers' knowledge, attitude, and practice of safe pesticide use. Secondly, I examined the structural constraints to regulating pesticide usage and promoting safe practices, based on interviews with local health care providers and key officials in agriculture, health, and agro-business. The research proved that acute pesticide poisoning is widespread in Jamaica. Furthermore, health outcomes varied geographically particularly as related to the nature of the crop and pest problems. There was some effort within the agricultural and medical branch of the Jamaican government to address this concern; however, evidence that farmers had widely adopted safe application practices did not exist. I found that hazardous pesticide practices were not simply traced to farmers' ignorance. Rather, farmers showed substantial awareness of safety procedures but often chose not to practice them. The matter was further complicated by the general lack of knowledge among health care providers in identification and proper treatment of poisoning. / Master of Science