Distribution and toxicity of sediment-associated pesticides in agriculture-dominated water bodies of California's Central Valley

The agricultural industry and urban pesticide users are increasingly relying upon pyrethroid insecticides and shifting to more potent members of the class, yet little information is available on residues of these substances in aquatic systems under conditions of actual use. Seventy sediment samples were collected over a 10-county area in the agriculture-dominated Central Valley of California, with most sites located in irrigation canals and small creeks dominated by agricultural effluent. The sediments were analyzed for 26 pesticides including five pyrethroids, 20 organochlorines, and one organophosphate. Ten-day sediment toxicity tests were conducted using the amphipod Hyalella azteca and, for some samples, the midge Chironomus tentans. Forty-two percent of the locations sampled caused significant mortality to one test species on at least one occasion. Fourteen percent of the sites (two creeks and four irrigation canals) showed extreme toxicity (>80% mortality) on at least one occasion. Pyrethroid pesticides were detected in 75% of the sediment samples, with permethrin detected most frequently, followed by esfenvalerate > bifenthrin > lambda-cyhalothrin. Based on a toxicity unit analysis, measured pyrethroid concentrations were sufficiently high to have contributed to the toxicity in 40% of samples toxic to C. tentans and nearly 70% of samples toxic to H. azteca. Organochlorine compounds (endrin, endosulfan) may have contributed to the toxicity at a few other sites. This study provides one of the first geographically broad assessments of pyrethroids in areas highly affected by agriculture, and it suggests there is a greater need to examine sediment-associated pesticide residues and their potential for uptake by and toxicity to benthic organisms.     

Pyrethroid insecticides and sediment toxicity in urban creeks from California and Tennessee

Pyrethroid pesticides have replaced organophosphates for many urban applications, including structural pest control, landscape maintenance, and residential home and garden use. This study was intended to determine if pyrethroids are detectable and widespread in diverse urban systems and if concentrations are high enough to cause associated aquatic toxicity. Urban creeks in California and Tennessee were tested on up to four occasions for pesticide residues in sediments, and aquatic toxicity was determined by acute toxicity tests using the amphipod, Hyalella azteca. In California, 12 of the 15 creeks tested were toxic on at least one sampling occasion, and sediment pyrethroid concentrations were sufficient to explain the observed toxicity in most cases. The pyrethroid bifenthrin, due to its high concentrations and relative toxicity as compared to other pyrethroids, was likely responsible for the majority of the toxicity at most sites. Cypermethrin, cyfluthrin, deltamethrin, and lambda-cyhalothrin also contributed to toxicity at some locations. The source of cypermethrin and deltamethrin was probably almost entirely structural pest control by professional applicators. Bifenthrin, cyfluthrin, and lambda-cyhalothrin may have originated either from professional structural pest control or from lawn and garden care by homeowners. None of the sediments collected from the 12 Tennessee creeks were toxic, and pyrethroids were rarely detectable. Regional differences between Tennessee and California are possibly attributable to climate, differences in types of residential development, and pesticide use practices.     

Occurrence and potential sources of pyrethroid insecticides in stream sediments from seven U.S. metropolitan areas

A nationally consistent approach was used to assess the occurrence and potential sources of pyrethroid insecticides in stream bed sediments from seven metropolitan areas across the United States. One or more pyrethroids were detected in almost half of the samples, with bifenthrin detected the most frequently (41%) and in each metropolitan area. Cyhalothrin, cypermethrin, permethrin, and resmethrin were detected much less frequently. Pyrethroid concentrations and Hyalella azteca mortality in 28-d tests were lower than in most urban stream studies. Log-transformed total pyrethroid toxic units (TUs) were significantly correlated with survival and bifenthrin was likely responsible for the majority of the observed toxicity. Sampling sites spanned a wide range of urbanization and log-transformed total pyrethroid concentrations were significantly correlated with urban land use. Dallas/Fort Worth had the highest pyrethroid detection frequency (89%), the greatest number of pyrethroids (4), and some of the highest concentrations. Salt Lake City had a similar percentage of detections but only bifenthrin was detected and at lower concentrations. The variation in pyrethroid concentrations among metropolitan areas suggests regional differences in pyrethroid use and transport processes. This study shows that pyrethroids commonly occur in urban stream sediments and may be contributing to sediment toxicity across the country.     

Selective treatments,including combinations of pyrethroid and organophosphorus insecticides. For control of stored product Coleoptera at two temperatures

Selective treatments, appropriate to simulated storage conditions, reinfestation pressures and species or strains of insects present in the wheat, required less insecticide than any “blanket” or all-purpose treatment. In particular, the pyrethroids bioresmethrin, synergized bioresmethrin or synergized pyrethrins were especially effective where Rhyzopertha dominica and especially a strain resistant to organophosphorus insecticides, was the only species present. Conversly, the organophosphorus insecticides dichlorvos, malathion, fenitrothion and pirimiphos-methyl were especially effective against Tribolium and Sitophilus species. There was no antagonism between any of the pyrethroids and any of the organophosphorus insecticides when they were applied in combination, in that the period of protection given by combinations was the period of protection given by the pyrethroid component against R. dominica and the organophosphorus component against Tribolium and Sitophilus species. As an example of the data required for selective treatments, bioassays were conducted at 20 and 30°C and it was found that the net effect of the lower temperature in reducing toxicity but increasing persistence was to increase the period of protection given by insecticides in cooled storages. It is suggested that the amounts of insecticides applied to grain could be considerably reduced if more consideration was given to grain conditions, if reinfestation pressures were more carefully examined and if less attention were given to surviving adults under conditions where progeny do not develop.     

Identifying the causes of sediment-associated toxicity in urban waterways of the Pearl River Delta, China

Twenty-one sediments collected in urban waterways of the Pearl River Delta (PRD) in China were screened for acute toxicity using Chironomus dilutus in addition to being examined for potential contributors of sediment toxicity, including 19 organochlorine, five organophosphate, and nine pyrethroid insecticides, 28 polycyclic aromatic hydrocarbons, 27 polychlorinated biphenyls, 15 polybrominated diphenyl ethers, 12 metals, and ammonia. Fifteen of the 21 sediments exhibited acute toxicity to C. dilutus, with 33% of the samples exhibiting 100% mortality. This is one of the first studies in China which directly correlates a broad range of sediment-associated contaminants to ecological effects measured by bioassays. A toxic unit approach showed that pyrethroids contributed most to the observed toxicity; as cypermethrin alone was predicted to cause significant mortality in about half of the sites. Specific toxicity identification evaluation analysis confirmed pyrethroid toxicity. Other contaminants may also be supplemental contributors at a few sites. The current study suggests that pyrethroids are the principal cause of contamination and that future risk assessment and mitigation efforts in this area should focus primarily on pyrethroids but should not disregard other contaminants as potential risk is evident.     

Determination of Pyrethroid Insecticides in Crude and Canned Vegetable Samples by Supercritical Fluid Chromatography

A supercritical fluid chromatography method for the determination of seven pyrethroid insecticides (allethrin, resmethrin, phenothrin, permethrin, tetramethrin, cypermethrin, deltamethrin) and one of their common metabolites, phenoxybenzyl alcohol, in whole and peeled potatoes and mixed vegetables was developed. The efficiencies of the two extraction techniques, supercritical fluid extraction and microwave-assisted extraction, for the extraction of pyrethroids from vegetable samples were also compared. The retention times of various pyrethroids ranged from 8.4 to 22.9 min, while all of the peaks were well-resolved and distinctly identified. The limits of detection of pyrethroid insecticides ranged between 0.31 and 0.54 ppm, whereas the limits of detection of phenoxybenzyl alcohol was 0.62 ppm. The recoveries of pyrethroid insecticides from whole potatoes, peeled potatoes, and mixed vegetables ranged as 93.83–99.8%, 92.3–105.8%, and 93.67–102.7%, respectively, with the use of supercritical fluid extraction. The corresponding recovery ranges while using microwave-assisted extraction were 94.2–102%, 96.6–101.2%, and 96–103.2%. These findings suggested that supercritical fluid chromatography was a sensitive and rapid technique for the analysis of pyrethroids in complex matrices, such as vegetables, fruits, and other agricultural products.     

Statewide investigation of the role of pyrethroid pesticides in sediment toxicity in California's urban waterways

A statewide investigation of urban creek sediment toxicity was conducted in California in recognition of increased incidences of toxicity linked to pyrethroid pesticides. The goals were to examine the spatial occurrence and magnitude of sediment toxicity in California urban creeks, and to examine the role of pyrethroids in toxic urban creek sediment samples. After a preliminary screening of 90 sites, 30 creeks were sampled in eight geographical regions. Sediment toxicity was assessed using 10 day bioassays with the resident amphipod Hyalella azteca. Bioassays were conducted at two test temperatures of 23 degrees C and at 15 degrees C to provide evidence of the cause of toxicity, and to more accurately reflect ambient environmental temperatures. Twenty-five of 30 samples were toxic when tested at 23 degrees C, and all 30 samples were toxic when tested at 15 degrees C. The magnitude of toxicity increased in samples tested at 15 degrees C suggesting the influence of pyrethroids, which are more toxic at colder temperatures. Pyrethroids were present in all sediment samples and were the only compounds detected at concentrations toxic to H. azteca. Bifenthrin was the pyrethroid of greatest toxicological concern, occurring in all 30 samples at concentrations up to 219 ng/g. Pyrethroid contamination of urban creeks was most severe in the Los Angeles, Central Valley, and San Diego regions, respectively. However, pyrethroids were also linked to urban creek aquatic toxicity in all regions sampled, including the less urbanized areas of the North Coast and Lake Tahoe.     

Control failure and insecticides resistance in populations of Rhyzopertha dominica (Coleoptera: Bostrichidae) from Colombia

The lesser grain borer Rhyzopertha dominica is a serious pest that causes significant economic damages in stored grains. The presence of this pest is mainly controlled using a small number of insecticides increasing risks of compromising the control efficacy due to the selection of resistant populations. Here, the control failure and potential resistance to pyrethroid and organophosphate insecticides frequently used for the control of R. dominica in Colombia were assessed. Concentration–mortality bioassays with synergized and unsynergized insecticides were used to assess potential metabolic-based pyrethroids resistance mechanisms. Based on the field recommended doses, the results revealed that while the pirimiphos-methyl is still efficient against R. dominica, both type I (i.e., bifenthrin) and type II (i.e., deltamethrin) pyrethroids presented control failure and their insecticidal activity was compromised. Although no differences in susceptibilities between the populations were found for the bifenthrin insecticide, the LC₅₀s of Ibagué (1.83 μl/gr of grains) and El Espinal (1.67 μl/gr of grains) populations were higher than the recommended rate. Furthermore, significant differences in susceptibility to deltamethrin resulted in resistance ratios RR₅₀ > 32-fold and RR₉₅ > 188-fold between the least (El Espinal) and the most (Ibagué) susceptible populations. Moreover, when synergized, the toxicity of deltamethrin was enhanced but resistance ratios kept at high levels (RR₅₀ > 11-fold and RR₉₅ > 40-fold) indicating possible existence of simultaneous metabolic and altered action-site mechanisms of resistance to pyrethroids in Colombian populations. Our results highlight the urgent need for nationwide monitoring of insecticides control failure and resistance in stored pests for better management schemes.     

Organophosphorus insecticides in agricultural and residential runoff: field observations and implications for total maximum daily load development

Development of total maximum daily loads (TMDLs) for nonpoint source pollutants requires mass flux estimates for targeted compounds from contributing sources. We measured organophosphorus insecticide concentrations in surface runoff from agricultural and residential land-use sites in a southern Californian watershed over the course of runoff-producing irrigation and rainfall events. Event mean concentrations (EMCs) for chlorpyrifos, diazinon, and malathion exhibited considerable variability among irrigation and storm runoff events at agricultural sites; residential storm runoff EMCs for these compounds were considerably less variable. Event loads and EMCs were higher for runoff events following reported insecticide applications. Organophosphorus insecticide EMCs were not consistently correlated with hydrologic characteristics of runoff events. Our results indicate that on an area basis, loads from residential land may exceed those from sites planted in row crops for a given rainfall depth, suggesting that residential land use warrants explicit consideration in TMDL development and implementation. No consistent first flush effect was discernible for organophosphorus insecticides in storm or irrigation runoff. A relative potency factor approach is introduced to permit evaluation of organophosphorus insecticides on a common toxicological basis and allow development of TMDLs and pollutant control strategies for these compounds as a class.     

Deltamethrin- and spinosad-mediated survival,activity and avoidance of the grain weevils Sitophilus granarius and S. zeamais

The granary and maize weevils are serious worldwide threats to stored products and their control has heavily relied on synthetic insecticides, which are largely recommended based on studies with acute lethal doses neglecting the importance of potential sublethal effects of insecticides. Deltamethrin has been widely used for managing grain weevils and other stored grain pest species, but reported control failures with this insecticide sparked the search for alternative insecticidal compounds. The bioinsecticide spinosad is one of such alternatives whose use against stored grain insect pests is relatively recent, but encompasses the control of grain weevils. Nonetheless, little is known about the sublethal effects of spinosad on these insect pest species. Here we assessed the insecticidal effects of commercial formulations of spinosad and deltamethrin against the weevil species Sitophilus granarius and S. zeamais. Both spinosad and deltamethrin were able to effectively control the insects, although the latter caused a faster mortality than the former. Behavioral pattern changes were caused by both insecticides, especially deltamethrin, triggering irritability (i.e., avoidance after contact). Different feeding and drinking responses were also detected for both weevil species, which exhibited significant avoidance to deltamethrin and to spinosad, but with a milder response to the latter. Apparently spinosad is not as easily recognizable as deltamethrin by S. zeamais and S. granarius, remaining effective against both species without minimizing as much the potential exposure as deltamethrin.     

Differential susceptibilities of two closely-related stored product pests,the red flour beetle (Tribolium castaneum) and the confused flour beetle (Tribolium confusum), to five selected insecticides

The red flour beetle (Tribolium castaneum Herbst) and the confused flour beetle (Tribolium confusum Jacquelin du Val) are among the most commonly encountered insects infesting stored food, but their susceptibilities to different insecticides often differ significantly, which complicates efforts to manage populations in milling and processing facilities. In this study, the susceptibilities of T. castaneum and T. confusum late-stage larvae to five selected insecticides, esfenvalerate, pyrethrins, dichlorvos, methoprene and pyriproxyfen, were assessed with and without synergists using topical applications. In four-day bioassays (without flour) with dichlorvos, esfenvalerate and pyrethrins, T. castaneum larvae were less susceptible (low larval mortality) to dichlorvos and esfenvalerate than T. confusum, whereas the reverse was true for treatment with pyrethrins. Pre-treatment with one of three synergists, piperonyl butoxide (PBO, cytochrome P450 monooxygenase inhibitor), S,S,S-tributyl phosphorotrithioate (DEF, esterase inhibitor), or diethyl maleate (DEM, glutathione S-transferase inhibitor), suggested involvement of esterases in the detoxification of dichlorvos and pyrethrins, and cytochrome P450 monooxygenases in the detoxification of esfenvalerate in both species. Interestingly, pre-treatment with some synergists increased the toxicity of insecticides in only one species: DEM and DEF increased the toxicity of dichlorvos to T. castaneum, whereas only DEF increased dichlorvos toxicity to T. confusum. In 28-day bioassays with larvae treated with each of two insect growth regulators (IGRs), methoprene and pyriproxifen, T. confusum was the more tolerant species. All T. castaneum died in either the larval or pupal stages with either IGR. In contrast, only pyriproxyfen caused complete mortality in T. confusum larvae, and even the highest dose of methoprene allowed nearly 70% of T. confusum larvae to pupate, and 4.5% of adults to emerge. Our results show that although these two species are closely related, they display very different susceptibilities to different insecticides, and different metabolic detoxification mechanisms may contribute to their differential insecticide susceptibilities.     

Gel filtration on sephadex LH-20. A general clean-up method for pesticides extracted from grain

Gel filtration on Sephadex LH-20 in ethanol was shown to be a practical method for the single stage clean-up of insecticide residues from grains. The advantage over previous column clean-up procedures is that one set of conditions is applicable to most insecticides. The process is thought to be particularly applicable where routine screening procedures are operated. The clean-up is adequate for thin-layer chromatography.     

Can SPME fiber and Tenax methods predict the bioavailability of biotransformed insecticides?

Recent studies recognize the ability of chemical techniques such as solid phase microextraction (SPME) fibers and Tenax extraction to predict bioavailability more effectively than exhaustive chemical extractions for sediment-associated organic contaminants. While the majority of research using these techniques studied legacy compounds such as PCBs and PAHs, there is great potential for these methods to work well for highly toxic, rapidly biotransformed compounds such as pyrethroid insecticides. The current study compared the ability of the two techniques to predict the bioavailability of permethrin and bifenthrin to two benthic invertebrates (Lumbriculus variegatus and Hexagenia sp.). In addition, variations in the application of the two techniques, specifically duration and conditions of exposure of the SPME fibers and duration of extraction with Tenax, were explored. The SPME fiber concentrations correlated strongly to both 6 and 24 h Tenax concentrations. The SPME fiber concentrations and 6 h and 24 h Tenax extractable concentrations correlated with both the parent permethrin and bifenthrin concentrations in the tissues of both species at steady state. Parent compound tissue concentrations for both species could be predicted with a single relationship for individual pyrethroids. This demonstrated the potential value of these methods to predict the bioavailability of compounds subject to biotransformation and application to multiple species.     

五种杀虫剂对烟草潜叶蛾的毒力测定

为筛选出有效的烟草潜叶蛾防治药剂,试验了5种药剂对烟草潜叶蛾卵及幼虫的毒力.研究结果表明,五种药剂对烟草潜叶蛾卵的毒力排序为三氟氯氰菊酯＞溴氰菊酯＞甲氨基阿维菌素苯甲酸盐＞高效氯氰菊酯＞氰戊菊酯;五种药剂对烟草潜叶蛾幼虫的毒力排序为三氟氯氰菊酯＞溴氰菊酯＞高效氯氰菊酯＞氰戊菊酯＞甲氨基阿维菌素苯甲酸盐.因此在防治中可选用三氟氯氰菊酯和溴氰菊酯对烟草潜叶蛾进行药剂防治.     

Allyl isothiocyanate actions on populations of Sitophilus zeamais resistant to phosphine: Toxicity,emergence inhibition and repellency

The risks associated with the use of synthetic insecticides have caused increased interest in the research of essential oils and their main constituents for use in the pest management of stored products. Allyl isothiocyanate (AITC) is the main component of mustard essential oil and has been reported as a potential replacement pesticide for conventional insecticides that control stored product insect pests. Here, we assessed the toxicity (including emergence inhibition) and repellent actions of AITC on Brazilian populations of the maize weevil Sitophilus zeamais (Coleoptera: Curculionidae) resistant to conventional insecticides (e.g., phosphine). We also evaluated physiological (e.g., respiration) and behavioral (e.g., walking and flight) traits of AITC-exposed insects. The AITC showed consistent insecticidal activity against the populations resistant to phosphine and other synthetic insecticides, with LC₅₀ values ranging from 1.5 to 2.9 μL L⁻¹. Significant inhibition of the offspring emergence was achieved after the exposure of parental adults to sublethal levels (i.e., LC₁ and LC₅) of AITC. Reductions in respiration rates were also registered in all the populations sublethally exposed to AITC. In all five populations, a high number of insects avoided AITC-treated (1.5 μL L⁻¹) grain masses, and although individuals of a phosphine-susceptible (i.e., Abre Campo) population increased walking and reduced flight activities, individuals of another phosphine-susceptible (i.e., Tunápolis) population exhibited higher flight activity under AITC exposure. Thus, our findings suggest that AITC is a potential tool that may be integrated into the control strategies of maize weevils where resistance to phosphine and other conventional insecticides is a problem.     

Toxicity and repellency of dimethoate,pirimiphos-methyl and deltamethrin against Tribolium castaneum (Herbst) using different exposure methods

Tribolium castaneum, the red flour beetle, is one of the major pests of cereal grains and their products. Infestation of raw food products by T. castaneum can be tackled by use of insecticides which offer a rapid and effective control method for different insect pests. In the present study, toxicity and repellency of three widely used insecticides was assessed on adult red flour beetles to investigate how a flour substrate affects the results of the standard laboratory toxicity and repellency test methods. The red flour beetles were exposed to the organophosphates dimethoate and pirimiphos-methyl and the pyrethroid deltamethrin, following the original and two modified residual film methods (toxicity assessment) and by the area preference method to assess repellency. Since the conditions of exposure (glass and filter paper surfaces as exposure substrates) in the original methods are quite different compared to the exposure carried out in stored-product protection, methods were modified to include flour as an exposure substrate. The results showed that according to the LC₅₀ values, toxicity of the investigated insecticides could be arranged in the following order: pirimiphos-methyl > dimethoate > deltamethrin. Also, both mortality and repellency were dependent on the exposure methods, i.e. presence and treatment of flour substrate. Mortality was significantly reduced in comparison to the original method. Repellency was recorded when beetles were exposed to deltamethrin using flour as a substrate, whereas using the filter paper surface (original method) repellency was not obtained. The results of the present study clearly indicate that there is an influence of substrate on the susceptibility of T. castaneum to insecticides and that the efficacy of different insecticides is affected by exposure substrate.     

不同发育虫态扁谷盗属对S-烯虫脂耐受性研究

扁谷盗属是一类世界性重要的储藏物害虫。目前由于抗药性、可用技术广谱性和成本较高等问题,使得该类虫害的防治受到严重的挑战。针对杀虫剂抗药性问题,我们积极采取了各种措施包括多样化杀虫剂方式,杀虫剂组合如保幼激素类似物(JHA)与其他药剂复配。保幼激素类似物(JHA),如s-烯虫酯,具有很好的安全性和对多种仓储害虫有效性的特点。了解影响可替代技术效果的关键因素才能进行有效的防治管理。此外,了解害虫所有发育阶段的耐药性表达非常重要,因为药剂应用环境中所有虫态都存在。我们测定了扁谷盗属不同虫态及其F1种群对s-烯虫酯的耐受性。从发育阶段来看,成虫耐受性最高,其次是卵,然后是幼虫,其耐受性与F1代中的蛹大致相同。通过比较不同虫种的结果表明,最敏感的是长角扁谷盗,而耐受性最高的是土耳其扁谷盗。当浓度达到30mg/L及以上,锈赤扁谷盗和长角扁谷盗孵化率均小于50%,而土耳其扁谷盗需达到80mg/L时孵化率才低于50%。在幼虫期,仅需施用5 ppm s-烯虫酯,三个扁谷盗虫种死亡率都超过50%。在试验期间,s-烯虫酯并未完全抑制扁谷盗后代的产生,但即使在0.5 ppm浓度下,也会导致所有扁谷盗属的成虫显著减少。本研究这些结论可以得出,s-烯虫酯对这三个虫种非常有效,可作为储粮害虫综合防治的潜在手段。     

Environmental transformations of silver nanoparticles: impact on stability and toxicity

Silver nanoparticles (Ag-NPs) readily transform in the environment, which modifies their properties and alters their transport, fate, and toxicity. It is essential to consider such transformations when assessing the potential environmental impact of Ag-NPs. This review discusses the major transformation processes of Ag-NPs in various aqueous environments, particularly transformations of the metallic Ag cores caused by reactions with (in)organic ligands, and the effects of such transformations on physical and chemical stability and toxicity. Thermodynamic arguments are used to predict what forms of oxidized silver will predominate in various environmental scenarios. Silver binds strongly to sulfur (both organic and inorganic) in natural systems (fresh and sea waters) as well as in wastewater treatment plants, where most Ag-NPs are expected to be concentrated and then released. Sulfidation of Ag-NPs results in a significant decrease in their toxicity due to the lower solubility of silver sulfide, potentially limiting their short-term environmental impact. This review also discusses some of the major unanswered questions about Ag-NPs, which, when answered, will improve predictions about their potential environmental impacts. Research needed to address these questions includes fundamental molecular-level studies of Ag-NPs and their transformation products, particularly Ag(2)S-NPs, in simplified model systems containing common (in)organic ligands, as well as under more realistic environmental conditions using microcosm/mesocosm-type experiments. Toxicology studies of Ag-NP transformation products, including different states of aggregation and sulfidation, are also required. In addition, there is the need to characterize the surface structures, compositions, and morphologies of Ag-NPs and Ag(2)S-NPs to the extent possible because they control properties such as solubility and reactivity.     

Persistent organochlorine pesticide levels in cow's milk samples from tropical regions of Mexico.

Organochlorine pesticides have been used in agriculture as a seed dresser, in sanitation, in malaria control programmes and in livestock to combat ectoparasites. Their residues accumulate in lipid-rich tissues due to their chemical stability and persistence. In the body they circulate throughout all compartments, deposit themselves in adipose fat and can be excreted during lactation. These pesticides are applied in tropical zones and drift to areas where cattle graze. Therefore, analyses of cow's milk samples can serve as an indicator of environmental and cows' exposure to them. One hundred and fifty milk samples were taken each year in 1998 and 2001 and analysed to determine concentrations of HCB, beta-HCH, pp"-DDE, op'-DDT and pp'-DDT. Results obtained indicate that beta-HCH is one of the main contaminants (0.106 and 0.087 mg x kg(-1) on fat basis) followed by pp'-DDT (0.078 and 0.037 mg x kg(-1) on fat basis) and pp'-DDE (0.051 and 0.033 mg x kg(-1) on fat basis). The HCB and op'-DDT were detected in lower quantities respectively (0.008 and 0.006 mg x kg(-1), and 0.031 and 0.010 mg x kg(-1) on fat basis). When comparing the results obtained with those from the previous study, it was noted that DDT levels decreased significantly in 2001 as a result of the substitution of the organochlorine insecticides with pyrethroids sprayed by the Mexican Ministry of Health to combat malaria since 1999.     

食品中有机磷杀虫剂残留对人体健康的损害作用

综述了食品中有机磷杀虫剂残留对人体的急性毒性,遗传毒性,生殖毒性以及免疫毒性的作用,对我国食品中有机磷杀虫剂残留现状作了简要分析并提出控制措施。