Work with pesticides and organophosphate sheep dips

Pesticides are an important hazard in agriculture. In developed countries their use is strictly regulated. Risk assessment for new pesticides includes comparison of the potential exposures of spray operators and other farm workers with a reference value. Usually, this is derived from toxicological studies in animals with allowance for the uncertainties in extrapolating between and within species. Older pesticides undergo periodic reviews, for which epidemiological data may also be available. Unintentional fatal poisoning by pesticides is extremely rare in Britain. Documented reports of non-fatal acute poisoning are also uncommon, but there may be substantial under-ascertainment of minor incidents. Pesticides have been linked with various chronic diseases, but few associations have been clearly established. A particular concern recently in Britain has been the possibility that organophosphate insecticides can cause chronic neuropsychiatric illness.     

PXR-dependent induction of human CYP3A4 gene expression by organochlorine pesticides

OCP are xenobiotics which display various toxic effects on animal and human health. One of their effects is to bind and activate estrogen receptor alpha (ERalpha). We have previously studied the down-regulation of induced CYP1A1 (cytochrome P450) expression by this class of molecules in mammary carcinoma cells and shown the importance of ERalpha in this process. However, an alternative mechanism was suggested by those experiments in hepatoma cells. In this study, we have performed Northern blot and transient transfection assays in various cell lines and shown that OCP activate human pregnane X receptor (PXR) and subsequent CYP3A4 mRNA expression. This effect is mediated by the distal xenobiotic responsive element modulator of the promoter. The induction of CYP3A4 by OCP was dose-dependent within the 1-10 microM range. The data suggest that chronic exposure to OCP could alter a major metabolite pathway in human liver and putatively modify the pharmacokinetics of drugs and pollutants.     

Effects of a mixture of two insecticides in freshwater microcosms: I. Fate of chlorpyrifos and lindane and responses of macroinvertebrates

Effects of chronic application of a mixture of the insecticides chlorpyrifos and lindane were studied in indoor freshwater microcosms. The exposure concentrations (based on 0, 0.005, 0.01, 0.05, 0.1 and 0.5 times the LC50 of the most sensitive standard test organism for each compound) were kept at a constant level for four weeks. The calculated mean concentrations for chlorpyrifos were found to be almost at their corresponding nominal level during the treatment period. The mean calculated lindane concentrations, however, were found to be 15–40% higher than intended. In the post treatment period both insecticides dissipated fast (t _1/2: chlorpyrifos 9 days, lindane 22 days) from the water phase. The concentrations of the mixture at the highest treatment level corresponded to 0.53 toxic units (TU) for Daphnia magna and 0.61 TU for the most sensitive fish. The decomposition of Populus leaves in litter bags was significantly lower at the three highest insecticide concentrations. The macroinvertebrate community was seriously affected at the three highest treatment levels, with Crustacea and the Chironomidae Corynoneura proving to be the most sensitive groups. Gastropoda and Oligochaeta were relatively insensitive and some taxa (e.g. Valvata piscinalis, juvenile Physa fontinalis, Nemertea and Stylaria lacustris) increased in numbers. The observed effects could be explained from the individual toxicity of the insecticides to the invertebrates, and did not indicate synergistic effects. A second paper (Van den Brink et al., 2002) addresses the effects on other endpoints, as well as the overall risk assessment of the insecticide mixture.     

Effects of a mixture of two insecticides in freshwater microcosms: II. Responses of plankton and ecological risk assessment

This paper reports on the chronic effects of a mixture of the insecticides chlorpyrifos and lindane in freshwater microcosms. Chronic treatment levels corresponding to concentrations of 0, 0.005, 0.01, 0.05, 0.1 and 0.5 times the LC50 of the most sensitive standard test organism were evaluated. The zooplankton community structure was altered from the 0.05*LC50 treatment level upwards. Cladocerans were the most susceptible group, followed by Copepoda and Ostracoda. Rotifera increased in abundance at the higher treatment levels. Increased abundance of some phytoplankton taxa and increased chlorophyll-a levels were found at the two highest treatment levels, most probably a consequence of decreased grazing pressure. Threshold levels for the mixture, both at population and community/ecosystem level, corresponded well with those reported in the literature for the individual compounds. The overall risk assessment indicates no antagonistic or synergistic effects of the mixture at ecosystem level. It was found that the safety factors set by the Uniform Principles for individual compounds also ensure protection against chronic exposure to a mixture of insecticides at community level, though not always at species level.     

The organochlorine pesticide residues and antioxidant enzyme activities in human breast tumors: is there any association?

The levels of some organochlorine pesticides (OCP)s (hexachlorobenzene, HCB, -hexachlorocyclohexane, -HCH, -HCH, -HCH, heptachlorepoxide, HE, bis (4-chlorophenyl)-1,1-dichloroethene, p.pDDE, bis (4-chlorophenyl)-1,1,1-trichloroethane, p.p DDT and total DDT (-DDT) and antioxidant enzyme activities namely Cu, Zn superoxide dismutase (SOD), catalase (CAT), selenium-dependent glutathione peroxidase (Se-GSH-Px), total glutathione peroxidase (T-GSH-Px), selenium independent glutathione peroxidase (GSH-Px II), glutathione reductase (GRd), level of reduced glutathione (GSH) and lipid peroxidation (LP), glutathione S-transferase (GST) activity toward several substrates including 1-chloro-2,4-dinitrobenzene (CDNB), 1,2-dichloro-4-nitrobenzene (DCNB), ethacrynic acid (EAA), 1,2-epoxy-3-(p-nitrophenoxy)-propane (ENPP) were measured in tumor and surrounding tumor free tissues of 24 female breast cancer patients and was evaluated whether there exist any association between the levels of OCPs and antioxidants. The mean levels of GSH, -BHC, -BHC and HE, and activities of SOD, Se-GSH-Px, T-GSH-Px, GSH-Px II,GRd, GST CDNB, and GST DCNB were significantly higher in tumors than in controls. In tumors, significant correlations were noted between: SOD and -BHC; Se-GSH-Px and -BHC; T-GSH-Px and -BHC; GSH-Px II and -BHC, -BHC; GSH and -BHC, -BHC, HE; GRd and -BHC; CDNB GST and -BHC, -BHC. These results show that free-radical mediated oxidative stress is, at least partly, associated with some of these OCP residues in human breast tumors.     

固相萃取GC/MS法测定血中25种有机磷农药的方法研究

目的：建立一种同时测定中毒血样中25种有机磷农药的固相萃取净化GC／Ms方法。方法：血样中加入异丙威内标物，丙酮提取有机磷农药，采用Oasis HLB固相小柱净化，用毛细柱气相色谱分离，采用选择离子监测（SIM）的质谱扫描模式进行定量分析。结果：25种有机磷农药检测限为20～30ng／ml，定量限为60～90ng／ml，血样加标100～1000ng／ml的平均回收率为48．9％～98．9％，重复测定6次的rsd值小于10％，血样中OPs在加入EDTA二钠盐后在-20℃条件下保存稳定。结论：该方法具有较高的灵敏度、准确度和精密度，可满足中毒血样中有机磷农药快速检测分析的要求。建立一种同时测定中毒血样中25种有机磷农药的固相萃取净化GC/MS方法。     

瓜蒌中有机氯农药残留量测定研究

目的：测定瓜蒌中有机氯农药残留。方法：利用气相色谱法同时测定瓜蒌中9种有机氯农药的残留量。结果：方法回收率为78．0％－102．0％，RSD＜10．0％，所测10个样品中总BHC及总DDT含量＜0．05μg/g。结论：测定结果可见本法符合农药残留分析要求，但应制定相应限量标准。     

浅谈中药材的农药重金属污染与防治

中药材中的农药、重金属残留和污染巳严重影响药材的质量，成为中药走向世界的“瓶颈”，本文论述了中药材中农药、重金属残留和污染产生的原因并提出了有关的解决措施，本文实践性强，可供广大药材种植基地科技人员借鉴。     

血液灌流治疗急性有机磷农药中毒临床研究

目的应用血液灌流（hemoperfusion,HP）治疗急性有机磷农药中毒（acute organophosphorus pesticides poisoning,AOPP）观察其临床意义。方法39例急性有机磷农药中毒患者分为两组。治疗组：急性重度AOPP中毒20例,在其他综合治疗的基础上及时行床边血液灌流治疗,观察血胆碱酯酶（choline esterase,chE）的变化及治疗效果。对照组：同期收治的因为非医疗原因未能行HP治疗的19例重度AOPP,比较观察两组chE恢复时间、脱呼吸机时间、并发肺部感染、住院时间、成活率、住院费用。结果与对照组相比,HP治疗组chE恢复时间快、脱机时间早、成活率高、住院时间短、总住院费用少。结论血液灌流对于急性药物中毒有良好疗效。