Inter- and Intra-Species Extrapolation in Risk Assessment of Different Classes of Pesticides

Risk assessors routinely use the reference dose (RfD) approach for non-cancer risk assessment. In this approach, No-Observed-Adverse-Effect-Level (NOAEL) is divided by the product of uncertainty factors (UFs) and, occasionally, an additional modifying factor (MF), each usually employed by default as factors of 10. In the present investigation, kinetic and dynamic data have been used in order to reduce uncertainties when establishing exposure guidelines for examples of chemicals representing four classes of pesticides (warfarin, lindane, carbaryl and parathion). An intensive search of databases was conducted for these pesticides, and toxicokinetic and toxicodynamic parameters in inter- and intra-species were evaluated. The kinetic and dynamic subfactors were less than the proposed values of Renwick and the International Programme on Chemical Safety (IPCS). The composite factors for all the examined pesticides were less than 100. The present study indicated that in setting exposure levels it is important to incorporate kinetic and dynamic data, as they become available, rather than rely on default uncertainty factors, which are imprecise in many cases.     

Pesticides and heavy metals in Danish streambed sediment

The role of streambed sediment as a sink for pesticides and heavy metals was investigated in 30 Danish lowland streams. The investigated streams drain catchments varying in hydrology, topography, soil type and land use. The <250 m newly accumulated fraction of the uppermost 1–2 cm layer of streambed sediment was analysed for 19 old and modern pesticides and 9 heavy metals. DDE was present in the sediment of all the streams. Of the herbicides, fungicides and insecticides currently in use, the most frequently detected was diuron (50.0%), fenpropimorph (66.7%) and lambda-cyhalothrin (6.7%), respectively. The pesticides detected in the highest concentration were fenpropimorph (1700 ng g^–1), propiconazole (130 ng g^–1) and isoproturon (110 ng g^–1). The heavy metals are listed in order of increasing median concentration: Cd (0.80 g g^–1), Co (9.1 g g^–1), As (12.0 g g^–1), Ni (19.0 g g^–1), Cr (19.2 g g^–1), Pb (19.7 g g^–1), Cu (20.1 g g^–1), V (28.5 g g^–1), Zn (103 g g^–1). The average number of pesticides detected in the 27 streams draining predominantly agricultural catchments was (3.7±2.0) being higher (p=0.077) than in the three streams draining non-agricultural catchments (1.7±0.6). Pesticides were significantly related to catchment size, soil type and hydrological regime. Several heavy metals (Cr, Cu, Pb, V and Zn) were related to urban activity and soil type.     

The Life-Cycle of Chlorine, Part IV

Some cyclic organo-chlorines share key characteristics to a significant degree, notably volatility, solubility in lipids, environmental persistence, a tendency to bioaccumulation, and toxicity to animals. A subset of this group has been designated "persistent organic pollutants" (POPs). Because of their volatility, persistence, and tendency to bioaccumulate, POPs are found in remote locations, such as the Arctic, far from the locations where they were initially used or produced.
Except PCDDs (dioxins) and PCDFs (furans), all are, or were, originally produced for use as such , mainly as pesticides or herbicides. PCDDs and PCDFs have never been produced for their own sake; they are unwanted contaminants of chemical intermediates that were passed on and incorporated in final products, notably herbicides; they are also generated spontaneously in most combustion processes and chlorine bleaching of paper. Most POPs have been sharply restricted or banned outright in most of the industrialized countries, but not in less developed countries.
The qualities of persistence and bioaccumulation give special urgency to monitoring not only point source emissions and local concentrations, but also the mobile environmental reservoirs and exposure routes of these chemicals. To conduct adequate risk analyses, far more detailed data is needed on quantities produced and used, quantities and location of storage, mode of use, location of use, and period of use. Such data are not collected consistently by government or international agencies.     

Toxicity of pesticides to the citrus leafminer and its parasitoid Ageniaspis citricola evaluated to assess their suitability for an IPM program in citrus nurseries

The relative toxicity of pesticides to Phyllocnistis citrella and its parasitoid Ageniaspis citricola was compared by several bioassay methods. A clip-cage bioassay measured survival of adults exposed to fresh residues at 0.25-times (0.25×), 0.5×, 1×, and 2× the lowest recommended rate of each pesticide, a water control (0×), and 24- and 48-h aged residues of oil at 1.5% (1×) rate. A one-species cylinder bioassay determined the effects of pesticides on immature stages of the citrus leafminer after treating young citrus trees with the same rates of pesticides (except for avermectin, tested at 0×, 0.01×, 0.025×, 0.05×, 0.1×, and 0.25× rates). A sublethal rate of petroleum oil (0.4%) was added as an adjuvant in some treatments. The effect of pesticides on immature stages of A. citricola was determined with a two-species cylinder bioassay after treating young citrus trees with the same rates as above. An index of IPM compatibility was developed based on the efficacy of the pesticide as a control agent of the leafminer (or other pests) and its selectivity to the parasitoid at the lowest recommended field rate (0.25× the field rate for avermectin). Azadirachtin (Neemix) + oil, diflubenzuron (Micromite) + oil, fenoxycarb (Eclipse) + oil, and oil alone (FC 435-66) were classified as IPM-compatible insecticides. Sprays of azadirachtin (Align) + oil, neem oil (Neemgard), and drenched imidacloprid (Admire) were ranked as a semi-compatible insecticides. The fungicide copper hydroxide (Kocide 101) and a fish oil-based foliar fertilizer (Zapata HFE) were considered compatible. Avermectin (Agri-Mek) + oil, ethion (Ethion), and imidacloprid (Provado) applied as a spray were IPM-incompatible insecticides. These products should be tested under field conditions to confirm these ratings.     

Evaluation and application of aquatic toxicity tests: use of the Microtox test for the prediction of toxicity based upon concentrations of contaminants in soil

The quality control for the reuse of cleaned soil from a contaminated site consisted in the determination of the main contaminants by analytical chemical methods such as GC and HPLC. Since it is not possible to analyze for all contaminants a toxicity test should be used to detect large concentrations of not routinely analyzed chemicals. The aim of the study was to develop a system for toxicity testing, which should be able to predict the toxicity of soil samples based on the concentration of chemicals in the soil and to detect toxic chemicals not analyzed by the routinely conducted soil analysis.Based upon the relative sensitivity to various contaminants as well as practical aspects such as test duration and costs the Microtox® test was favoured over the bioassays with Daphnia magna and Scenedesmus subspicatus. The Microtox® test was used to measure the toxicity of various pesticides and their major metabolites. The toxicity data of the pure compounds were used to predict the toxicity (EC₅₀ and % inhibition of the bioluminescence reaction) of defined mixtures of chemicals in water by applying two different mathematical appriaches which are based on the additivity of the effects of the single chemicals. The predicted values were compared with the experimental data and showed good agreement.In order to be able to predict the toxicity of soil samples using the Microtox® test the soil/water partition coefficient (K _d) was measured for the main contaminants. The toxicity of soil samples was predicted by calculating the concentration of the contaminants in the leachate by using the corresponding concentration in the soil and applying the K _d values determined. From the calculated composition of the leachate the expected toxicity was estimated. This value was compared with the toxicity experimentally determined in the Microtox® test.     

中国植物质杀虫剂的研究(英语)

本文主要集中反映及讨论中国植物质杀虫剂近年主要的研究成果.内容包括:印楝、苦楝、川楝、黄杜鹃、毛鱼藤、非州山毛豆、紫背金盘及其它杀虫植物.还讨论了植物质杀虫剂的活性及在害虫防治上的应用.     

Analysis of a laboratory method to test the effects of pesticides on adult females of Opius concolor (Hym., Braconidae), a parasitoid of the olive fruit fly,Bactrocera oleae (Dip., Tephritidae)

The laboratory test described in the present paper assesses pesticide effects on the ‘most exposed’ life stage of the parasitic wasp Opius concolor, and it has been developed and interpreted according to the guidelines of the IOBC/WPRS Working Group ‘Pesticides and Beneficial Organisms ‘. The evaluation of results is based on longevity and parasitism of adult females exposed to afresh residue of pesticide on a glass surface. Longevity measurements were based on the time of exposure required to cause 50% mortality (LT₅₀) and were compared to a standard control LT₅₀ in order to calculate the reduction caused by the pesticide. Parasitism was surveyed by means of three sequential determinations: the number of days that females were seen parasitizing, the mean number of attacked hosts and the progeny size per female. These determinations were also compared to a control to calculate the impact of pesticides. Using this ‘worst case’ situation, pesticides reducing the beneficial capacity of O. concolor below the IOBC threshold for harmlessness may be recommended for field use in combination with this wasp.     

Results of the sixth joint pesticide testing programme of the IOBC/WPRS-working group «pesticides and beneficial organisms»

The side effects of 5 insecticides, 8 fungicides and 6 herbicides on 24 species of beneficial organisms were tested by members of the Working Group «Pesticides and Beneficial Organisms» of the International Organization for Biological Control (IOBC), West Palaearctic Regional Section (WPRS). The tests were conducted by 24 members in 11 countries according to internationally approved guidelines. The insecticide buprofezin (Applaud), the fungicides triforine (Saprol), procymidone (Sumisclex), anilazine (Dyrene), triadimenol (Bayfidan), hexaconazole (Anvil), tridemorph (Calixin) and the herbicides tralkoxydim (Grasp), bentazone (Basagran) were harmless to nearly all the beneficial organisms. Diflubenzuron (Dimilin) affected spiders and the larvae of predatory insects. The remaining 10 preparations were more toxic and should therefore be further tested in semi-field and field experiment on relevant organisms.     

Assessment of the Chemical Quality of Recreational Bathing Water in Argentina by Health Risk Analysis

Del Azul creek (Argentina) is a natural water body used for recreational bathing in which heavy metals and pesticides have been detected. The aim of the study is to estimate the probabilistic non-cancer and cancer risks by recreational bathing, applying U.S. Environmental Protection Agency models for aggregated (exposure through accidental oral intake of water and dermal contact) and cumulative risks (combined exposure to groups of substances) for bathers of 5, 10, 15, and 20 years old. Bathing in Del Azul creek does not generate risks at the concentrations and the exposure scenarios considered. Cypermethrin and arsenic and heptachlor were the riskiest non-cancer and cancer substances, respectively. Our study highlights the importance of considering both routes of exposure because of the great significance of the dermal route and because of the variability of population characteristics, as it has been stated in other studies. These considerations are highly significant for Argentina, where the quality of recreational water for other than microbiological causes is frequently evaluated based only on the harmful oral intake and applied to a hypothetical individual representative of the population.     

Detoxification of organophosphate nerve agents by immobilized dual functional biocatalysts in a cellulose hollow fiber bioreactor

A whole-cell technology for detoxification of organophosphates based on genetically engineered Escherichia coli cell expressing both cellulose-binding domain (CBD) and organophosphorus hydrolase (OPH) onto cell surface was reported recently (Wang et al., 2002). This study reports the application of these biocatalysts when immobilized in a cellulose hollow fiber bioreactor (HFB) for the biodetoxification of a model organophosphate, paraoxon, in a continuous flow mode. In 24 h, 0.79 mg wet cell/cm2 fiber surface were immobilized onto cellulose fibers specifically and strongly through the cellulose binding domain, forming a monolayer demonstrated by Scanning Electronic Micrograph, and essentially no cell was washed away by washing buffer. The immobilized biocatalyst had a high performance of detoxifying paraoxon solution of 5,220 mumol/h x L reactor or 990 mumol/h x m2 reactor. The immobilized biocatalysts maintained a stable degradation capacity for 15 uses over a period of 48 days with only 10% decline in degradation efficiency under operating and storage conditions. In addition, the bioreactor was easily regenerated by washing with 1% sodium dodecyl sulfate (SDS), with 86.7% immobilization capacity and 93.9% degradation efficiency recovery. This is the first report using the HFB in a non-traditional way, immobilizing whole-cell biocatalysts by specific adhesion thus rendering the catalysis operation the advantages of low pressure drop, low shear force, and low energy requirement. The successful application of this genetically engineered dual functional E. coli strain in a model bioreactor shows its promise in large-scale detoxification of organophosphate nerve agents in bulk liquid phase.