A perspective of pesticide residue variability and acute dietary risk assessment.

The question of the variability of pesticide residues and acute risk assessment has arisen in the context of the work of the European Commission's Scientific Committee for Plants (SCP). A brief outline is presented of European Community legislation on pesticide residues and the authorization of plant protection products. It is stated that although chronic risk assessment is systematically carried out in connection with the fixing of Community MRLs, the same has not applied for acute risk assessment. The reasons for this situation have been the absence of an agreed methodology, acute reference dose (RfD) and adequate dietary and residue data. It is stated that in the opinion of the Scientific Committee for Plants an acute risk assessment should be considered on a routine basis and that steps should be taken to ensure the availability of the necessary data. Possible implications for risk communication and the authorization of plant protection products in the EC are also discussed.     

How the variability issue was uncovered: the history of the UK residue variability findings

As a result of routine monitoring data on carrots generated in the 1990s indicating MRL exceedances, further studies showed that residues of organophosphorus compounds in individual roots could vary up to 25 times the levels found in composite samples. Additional work found that this phenomenon also extended to other crops including apples, peaches and celery. Variability (defined as the highest residue level found in any one crop item divided by the level found in a composite sample from the same batch) of up to 34 times mean values was found in one batch of plums. Conventional deterministic methods used in consumer assessments were likely to give gross overestimates of short-term exposure because of the assumptions employed. This led to the development of probabilistic models which made the best use of all available information and was capable of indicating percentages of consumers that could exceed relevant toxicological end points. This indicated that there was unlikely to be serious health effects as a result of ingesting these residues and has subsequently proved to be a useful aid to regulatory decision making.     

The US Food Quality Protection Act--policy implications of variability and consumer risk.

The passage of the Food Quality Protection Act (FQPA) in August of 1996 increased the role of risk assessment in the decision-making process of the US Environmental Protection Agency (EPA). Although the law and guidance issued by the EPA provide for more sophisticated risk assessments, the databases for many chemicals may not be robust enough for such data-sensitive analyses. FQPA mandated a major change in how the EPA evaluates the safety of pesticides. This change was immediate, without provision for a phase-in period. Consequently, the EPA is still in the process of learning how to evaluate pesticides under the new paradigm. The EPA's task was further compounded by the lack of scientifically tested methodologies for evaluating aggregate and cumulative risk, as required under the new law. Clearly, the EPA is still in a state of transition between evaluating aggregate and cumulative risks to pesticides and evaluating them one chemical and one exposure route at a time. In all likelihood, the transition period will continue as the discipline of risk assessment develops the mental constructs and computational methodologies to fulfil the requirements of the law. In this interim period, therefore, policies are needed so the regulators and the regulated industry know what is currently acceptable, and how the EPA's thinking is evolving.     

Residue variability and sampling practical problems and consequences for residues monitoring

Data generated in the UK have indicated that pesticide residue levels can be highly variable between the individual fruit or vegetables from the same crop or lot in trade. Statistical experiments with these data showed that residues in composite samples, taken according to Codex recommendations, are unlikely to differ by more than a factor of 3-4 from the mean level in the lot. This was corroborated by results obtained from real composite samples. Many fruit or vegetables in trade are mixed after harvest to form combined lots. Analysis of composite samples provides a good indication of average residues but, where the lot has been mixed, such average values are potentially misleading. Residues monitoring is the best means available for general control of pesticide use and consumer exposure, but new strategies for sampling and analysis are required to address the combined effects of residues variability and mixing of lots.     

A meta-analysis of variability in continuous-culture ruminal fermentation and digestibility data

A meta-analysis was conducted to compare ruminal fermentation and digestibility data and variability between continuous-culture (CC) experiments and in vivo data. One hundred eighty CC studies representing 1,074 individual treatments, published in refereed journals between 1980 and 2010 were used in this analysis. Studies were classified into 2 groups based on the type of CC used: CC systems specified as rumen simulation techniques (RUSITEC) and non-RUSITEC CC systems (non-RUSITEC). The latter was a diverse group of systems, all of which were termed CC by the investigators. The CC data were compared with a data set of in vivo trials with ruminally cannulated lactating dairy cows (data from a total of 366 individual cows). The reported neutral detergent fiber (NDF) concentration of the diets fed in the 3 data sets was, on average (dry matter basis), 44, 34, and 32%, respectively. The average total volatile fatty acid (VFA) concentration for the RUSITEC and non-RUSITEC data sets was 67 and 80% (respectively) of the total VFA concentration in vivo. The average concentration of acetate was also lower for the CC data sets compared with in vivo and that of propionate was considerably lower for RUSITEC compared with in vivo, but butyrate concentrations were similar between the CC and in vivo data sets. Variability in the VFA data was generally the highest (higher coefficients of variation and variance) for the non-RUSITEC data set, followed by RUSITEC, and was the lowest for in vivo. Digestibilities of NDF and particularly organic matter were lower in the CC data sets compared with in vivo; the average NDF digestibility was 34.2, 45.5, and 53.0% for RUSITEC, non-RUSITEC, and in vivo, respectively. Variability in nutrient digestibility data followed the pattern of variability of the VFA data: highest variability for the non-RUSITEC data set, followed by RUSITEC, and the lowest for in vivo. This analysis showed that CC systems are generally characterized by lower total VFA and acetate concentrations, extremely low counts or lack of ruminal protozoa, and lower organic matter and NDF digestibilities than in vivo. Overall, variability was much greater for CC than for in vivo experimental data.     

Comparison of two field sampling procedures (En Core and field methanol extraction) for volatile organic compounds

In-situ Lasagna technology was recently evaluated at a contaminated site at Offutt Air Force Base. The site was contaminated with low levels (<30 mg/kg) of volatile organic compounds (VOCs). Originally, researchers planned to use field methanol extraction for both pre- and post-treatment sampling to evaluate the effectiveness of the technology on contaminant reduction. Precharacterization sampling, however, indicated that concentrations of some contaminants of concern were much lower than expected. Because use of methanol increases the detection limit, it was probable that post-treatment concentrations of these target contaminants would be nondetectable if methanol extraction was used. Project management, therefore, decided to use En Core samplers in addition to field methanol extraction during the pretreatment sampling event. The En Core sampling approach, while yielding a lower detection limit, uses discreet samples along the length of a core, whereas the methanol extraction approach samples the entire length of the core. The concern was that discreet samples may bias results if any "hot spots" were present. The two field sampling procedures, En Core and field methanol extraction, were performed side-by-side during the pretreatment phase of the technology evaluation in order to determine if the concern was valid for this site. Results were compared for four contaminants of concern: trichloroethylene, vinyl chloride, cis-1,2-dichloroethene, and trans-1,2-dichloroethene. The two procedures produced similar results with respect to both the concentration means and the variances, and no bias was evident. This finding supports project management's decision to use only En Core samplers post-treatment due to low concentrations of target contaminants.     

Making best use of available residue data for acute intake assessment

Risk assessment for pesticide residues in food has previously concentrated on chronic intake, probably with the assumption that if the chronic intake is acceptable, acute intake will also be acceptable. Data generation is expensive so we should extract, where possible, information useful for acute intake estimation from supervised residue trials. Residues in individual units of fruit or vegetables are more variable than the residues in composite samples and the distribution in individual units is probably best approximated by a lognormal distribution, but further evidence is needed. Theory provides a method for calculating the variability of replicate composite samples and applying it to individual units. The expected residue in the 95th or 99th percentile single fruits may then be calculated. An example for folpet residues in apples showed that the 95th and 99th percentile apples would contain 1.8 x and 2.3 x the residue in the composite sample, respectively. For abamectin in apples the 95th and 99th percentile factors were 6.7 and 15, respectively. The 95th and 99th percentile factors for azinphos-methyl in apples, based on single apple analysis, were 1.7 and 2.1, respectively.     

环境监测现场采样质量控制措施研究

现场采样是环境监测的重要环节,能够为环境监测提供必要的参考数据和决策依据,从而进行更加科学、全面的环境评价,对于提升环境监测质量具有重要意义.但是由于现场采样受到多种因素的影响,导致采样质量不稳定因素增多,严重影响环境监测的最终效果.因此,强化对环境监测现场采样质量控制措施的研究势在必行.本文主要分析了环境监测现场采样...     

Locating and quantifying PCB sources in Chicago: receptor modeling and field sampling

Potential source contribution function (PSCF) modeling using polychlorinated biphenyl (PCB) concentrations measured in the Chicago area resolved three PCB source sectors. They were (i) the direction northwest of Chicago, (ii) the direction southwest of Chicago, and (iii) the south side of Chicago in the neighborhood of Lake Calumet. The area south of Chicago was further examined by taking upwind/ downwind samples near a landfill and sludge drying beds. Results identified the sludge drying beds and a large landfill as PCB sources to the atmosphere. Another PCB source identified in Chicago was a transformer storage yard. This site had the highest upwind/downwind concentration increments in this study (downwind PCB concentrations were more than 5 times those in the upwind air). These PCB sources were characterized in terms of inventories, emission rates, contributions, and PCB congener profiles (fingerprints). Preliminarily results indicate that the sludge may emit up to 90 kg/yr of PCBs to the air. This amount is probably not a significant contribution of PCBs to the Chicago atmosphere on the basis of dispersion modeling results and a simple box model.     

The variability of urinary cotinine levels in young children: implications for measuring ETS exposure.

This study examined the within-subject variability of urinary cotinine levels in young children (aged = 0.6-7.2 years) of smoking parents to determine the number of urine samples needed to provide accurate estimates of exposure to environmental tobacco smoke (ETS) for different time intervals. Secondary analyses were conducted of five independent studies (N = 376), in which multiple urinary cotinine measures had been collected over time periods up to 13 months. Over measurement periods of 4-15 days, the within-subject cotinine levels varied 3-5 times more than would be expected based on measurement error alone. Over 7-13 months, the within-subject variability was 10-20 times higher than would be expected based on the measurement error. Findings indicated that cotinine measures from single urine samples provided highly accurate estimates of only recent exposure (i.e., 2-3 days; rho = 0.99). To achieve similarly precise estimates of the mean cotinine level of an individual child over 4-15 days, up to nine urine samples may be necessary. Up to 12 urine samples may be required to achieve similarly precise estimates of ETS exposure over a 4- to 13-month period. Epidemiologic and clinical research on ETS exposure in children can benefit from multiple urine samples (a) to accurately measure average exposure at the level of the individual child, (b) to describe temporal patterns, (c) to detect incidences of peak exposure that would remain underrecognized if monitoring is limited to a single time point, and (d) to establish stable baseline levels and endpoints based on urine samples collected over clinically relevant time periods.     

Genetic variability of milk components based on mid-infrared spectral data

The aim of this study was to estimate the genetic parameters of the mid-infrared (MIR) milk spectrum represented by 1,060 data points per sample. The dimensionality of traits was reduced by principal components analysis. Therefore, 46 principal components describing 99.03% of the phenotypic variability were used to create 46 new traits. Variance components were estimated using canonical transformation. Heritability ranged from 0 to 0.35. Twenty-five out of 46 studied traits showed a permanent environment variance greater than genetic variance. Eight traits showed heritability greater than 0.10. Variances of original spectral traits were obtained by back transformation. Heritabilities for each spectral data points ranged from 0.003 to 0.42. In particular, 3 MIR regions showing moderate to high heritability estimates were of potential genetic interest. Heritabilities for specific wave numbers, linked with common milk traits (e.g., lipids, lactose), were similar to those estimated for these traits. This research confirms the genetic variability of the MIR milk spectrum and, therefore, the genetic variation of milk components. The objective of this study was to better understand the genetics of milk composition and, maybe in the future, to select animals to improve milk quality.     

缓坡植烟田土壤微量元素的空间变异特征

采用地统计学和地理信息系统(GIS)相结合的方法,对典型缓坡植烟田土壤有效微量元素含量的空间变异规律进行研究,并运用普通克里格(Kriging)进行最优无偏线性估计,绘制空间分布图。结果表明,研究区域4种微量元素含量均属于中等程度变异,变异性大小表现为Zn>Mn>Fe>Cu。土壤Fe和Zn的最适模型为指数模型;Mn和Cu为球状模型。土壤Cu和Zn块金系数分别为20%、23.7%,具有强烈的空间相关性;Fe和Mn为28%和43.5%,具有中等程度的空间相关性。各向异性分析表明,土壤Cu存在较强烈的各向异性,Mn的各向异性则较小。研究区4种土壤元素含量的低值均出现在坡度大的中北部,东北部较平缓的区域含量则较高;同一坡向下,坡度是影响微量元素含量空间分布的重要地形因素。因此,在山地烟田精准施肥决策中应考虑坡度等地形因素对微量元素空间变异的影响。     

Problems of Salmonella sampling.

Modern husbandry practices, regional concentration of the industry, high stocking densities, uniform age-distribution of birds and continuous feeding promote the spread of poultry diseases. Moreover, the immature state of the intestinal microflora or disturbance of the developing flora by antibiotics increases susceptibility of chicks to salmonellas. If an estimate of the number of salmonella-positive birds in a flock is needed, then the required number of samples can be assessed by using the binomial distribution function. Whenever a qualitative result is sufficient, the samples can be pooled or the flock litter can be sampled using an 'overshoe method', which is a novel, low-cost and rapid technique. An optimal pooling factor can be assessed at low prevalence levels (less than 10%). Serological methods will only detect the presence of antibodies to invasive strains of Salmonella. The sampling interval depends on the strategy of the Salmonella Control Programme. Breeder flocks should be sampled more frequently than meat flocks and laying flocks. The new salmonella standard, ISO 6579-1990, is applicable in the poultry industry. When bacterial numbers are likely to be low, or the organisms in a stressed condition, a pre-enrichment step should be included. In the case of faecal samples, however, pre-enrichment should be omitted. A whole carcass rinsing and massaging method is preferred for the examination of finished carcasses.     

绵羊服装革湿热舒适性与取样部位关系的研究

按照ISO2418—2004的规定对绵羊服装革臀背、颈、腹、腹肷部位革进行取样,分别测定其透气、透水汽、耐汗及保暖性能,分析湿热舒适性在整张皮革中存在的部位差,并将各部位湿热舒适性的平均值与ISO2418—2004中取样部位的测定值进行分析比较。试验发现：颈、腹肷部革能分别反映铬鞣绵羊整革的透水汽性、保暖性能：腹部革可以反映铬鞣绵羊整革的透气性和耐汗性。同时,对绵羊革各部位产生湿热性能差异的原因进行了分析,希望为服装厂合理使用皮革提供科学数据,避免不必要工序、资源的浪费,也为我国服装革的标准工作提供数据支持。     

Application of solid-phase microextraction for in vivo laboratory and field sampling of pharmaceuticals in fish

Previous field studies utilizing solid-phase microextraction (SPME) predominantly focused on volatile and semivolatile compounds in air or water. Earlier in vivo sampling studies utilizing SPME were limited to the liquid matrix (blood). The present study has expanded the SPME technique to semisolid tissues under laboratory and field conditions through the investigation of both theoretical and applied experimental approaches. Pre-equilibrium extraction and desorption were performed in vivo in two separate animals. Excellent linearity was found between the amounts extracted by SPME from the muscle of living fish and the waterborne concentrations of pharmaceuticals. A simple SPME method is also described to simultaneously determine free and total analyte concentrations in living tissue. The utility of in vivo SPME sampling was evaluated in wild fish collected from a number of different river locations under varying degrees of influence from municipal wastewater effluents. Diphenhydramine and diltiazem were detected in the muscle of fish downstream of a local wastewater treatment plant. Based on this study, SPME demonstrated several important advantages such as simplicity, sensitivity, and robustness under laboratory and in vivo field sampling conditions.     

A contribution to reduce sampling variability in the evaluation of deoxynivalenol contamination of organic wheat grain

Fusarium head blight caused by different varieties of Fusarium species is one of the major serious worldwide diseases found in wheat production. It is therefore important to be able to quantify the deoxynivalenol concentration in wheat. Unfortunately, in mycotoxin quantification, due to the uneven distribution of mycotoxins within the initial lot, it is difficult, or even impossible, to obtain a truly representative analytical sample. In previous work we showed that the sampling step most responsible for variability was grain sampling. In this paper, it is more particularly the step scaling down from a laboratory sample of some kilograms to an analytical sample of a few grams that is investigated. The naturally contaminated wheat lot was obtained from an organic field located in the southeast of France (Rhône-Alpes) from the year 2008–2009 cropping season. The deoxynivalenol level was found to be 50.6 ± 2.3 ng g^–1. Deoxynivalenol was extracted with a acetonitrile–water mix and quantified by gas chromatography-electron capture detection (GC-ECD). Three different grain sampling techniques were tested to obtain analytical samples: a technique based on manually homogenisation and division, a second technique based on the use of a rotating shaker and a third on the use of compressed air. Both the rotating shaker and the compressed air techniques enabled a homogeneous laboratory sample to be obtained, from which representative analytical samples could be taken. Moreover, the techniques did away with many repetitions and grinding. This study, therefore, contributes to sampling variability reduction in the evaluation of deoxynivalenol contamination of organic wheat grain, and then, at a reasonable cost.     

Field validation of a milk-line sampling device for monitoring milk component data

The objective of this study was to investigate the ability of a milk-line sampling device to obtain a representative sample under field conditions by comparing the milk component composition between milk-line and bulk-tank samples, for milk harvested from the same group of cows at the same milking. A total of 42 paired milk-line and bulk-tank samples were collected at separate milking events from 21 different dairy herds. Samples were analyzed for milk fat (%), true protein (%), and milk urea nitrogen (mg/dl). Concordance correlation coefficients showed a very high level of agreement between the two sample types, with values ranging between 0.82 and 0.95 for the components measured. ANOVA showed that milk component data derived from milk-line samples were neither statistically nor numerically different from milk component data derived from bulk-tank samples. The strategy of monitoring milk component data through milk line sampling should provide dairy producers with inexpensive, timely, and accurate information that will help to improve ongoing nutritional monitoring programs for individual groups of cows within the dairy herd.     

Escherichia coli sampling reliability at a frequently closed Chicago Beach: monitoring and management implications

Monitoring beaches for recreational water quality is becoming more common, but few sampling designs or policy approaches have evaluated the efficacy of monitoring programs. The authors intensively sampled water for E. coli (N=1770) at 63rd Street Beach, Chicago for 6 months in 2000 in order to (1) characterize spatial-temporal trends, (2) determine between and within transect variation, and (3) estimate sample size requirements and determine sampling reliability. E. coli counts were highly variable within and between sampling sites but spatially and diurnally autocorrelated. Variation in counts decreased with water depth and time of day. Required number of samples was high for 70% precision around the critical closure level (i.e., 6 within or 24 between transect replicates). Since spatial replication may be cost prohibitive, composite sampling is an alternative once sources of error have been well defined. The results suggest that beach monitoring programs may be requiring too few samples to fulfill management objectives desired. As the recreational water quality national database is developed, it is important that sampling strategies are empirically derived from a thorough understanding of the sources of variation and the reliability of collected data. Greater monitoring efficacy will yield better policy decisions, risk assessments, programmatic goals, and future usefulness of the information.