A Guide to Interpreting Soil Ingestion Studies. 1. Development of a Model to Estimate the Soil Ingestion Detection Level of Soil Ingestion Studies

Abstract

This paper provides a model to predict soil ingestion recovery values in soil ingestion studies either retrospectively or prospectively. The predictive equations generated from the model can be used to estimate minimum soil ingestion detection levels from soil ingestion studies which use mass-balance methods. The model is derived from data assessing soil recovery efficiencies in adults using eight different predictive tracer elements. The results constitute a methodology to determine minimum detection levels of soil ingestion, and hence have important regulatory significance.     

Soil Ingestion Estimates for Children in Anaconda Using Trace Element Concentrations in Different Particle Size Fractions

This investigation assessed the effect of soil particle size on soil ingestion estimates of children residing at a superfund site. Earlier research indicated that wide intertracer variability in soil ingestion estimates are based on soil concentrations with a soil particle size of 0 to 2?µm was markedly reduced when the estimates were based on soil tracer concentrations for a soil particle size of 0-250?µm. The reduced intertracer variation was principally attributed to changes in soil concentrations of only three of the soil tracers (i.e., Ce, La, Nd) which became concentrated in the finer particle size by approximately 2.5 to 4.0-fold. It was hypothesized that the intertracer agreement in soil ingestion estimates may continue to improve if the estimates are based on concentrations of tracers at finer particle sizes assuming that children ingest finer particles and that the above three tracers would continue to be further concentrated in the finer sized soil particles. The principal findings indicate: 1. The soil concentrations of Al, Si, and Ti do not increase at the two finer particle size ranges measured. 2. The soil concentrations of Ce, La, and Nd increased by a factor 2.5 to 4.0 in the 100 to 250?µm particle size range when compared with the 0 to 2?µm particle size range. No further substantial increase in concentration was observed in the 53 to 100 |jm particle size range. 3. The soil ingestion estimates are consistently and markedly changed only between the estimates based in 0 to 2?µm and 100 to 250?µm for Ce, La, and Nd. These changes reduced the intertracer variability in estimating soil ingestion, suggesting that the children eat finer soil particle sizes. 4. Because the particle sizes for all tracers (except Zr) were only modestly affected at the 53 to 100?µm range, it was not possible to confidently resolve the particle size of soil ingested by the children. 5. Residual intertracer variability in soil ingestion estimates based on Ce, La, Nd are likely to be significantly affected by non-food, non-soil sources of these tracers (i.e., source error). 6. Soil ingestion estimates of this study will be more reliable when derived from the finer-sized particles.     

A Guide to Interpreting Soil Ingestion Studies. 2. Qualitative and Quantitative Evidence of Soil Ingestion

Abstract

Four major studies have attempted to qualitatively and quantitatively assess the extent of soil ingestion in children using the soil tracer methodology. The validity of the estimates of soil ingestion of each study was reevaluated in light of the inherent strengths and limitations of study design and/or execution as well as via a novel methodology to estimate the soil recovery variance of each tracer which then lead to the estimation of soil ingestion detection limits of each tracer for studies performing mass-balance analyses. Based on these analyses it is concluded that the Binder et al. (1986) and Van Wijnen et al. (1990) studies provide no convincing evidence to support qualitative and quantitative estimates of soil ingestion due to inherent limitations of their respective study designs. The Davis et al. (1990) and Calabrese et al. (1989) studies displayed convincing qualitative evidence of soil ingestion. However, the results indicate that the median soil ingestion estimates of Davis et al. were less reliable than those of Calabrese et al. The range of detection limits vary according to the tracer and the assumption of acceptable precision in recovery estimation. The minimum detection level of soil ingestion in children in the Calabrese et al. study with a variance in recovery of 100% ± 20% was 16 mg day^?1 based on Zr.

These findings are of particular regulatory significance since they provide: (1) a method of assessing the level of detection inherent in soil ingestion studies, (2) a reevaluation of the major soil ingestion studies in light of new methodology, and (3) guidance for future studies so that detection capacity can now be included in the presentation of study findings.     

Methodological Considerations in Soil Ingestion Estimation

Abstract

Methodological considerations play an important role in forming population estimates of soil ingestion in children. Two important areas of controversy are the hypothesized log-normal distribution of ingested soil and the identificatbn and appropriateness of methods for handling outliers. Each of these issues is discussed in the context of data collected on soil ingestion in Amherst, Massachusetts. Non-parametric methods are recommended as most suitable and appropriate for analysis of soil ingestion studies.     

Soil Ingestion Distributions for Monte Carlo Risk Assessment in Children

Monte Carlo environmental risk assessment requires estimates of the exposure distributions. An exposure of principal concern is often soil ingestion among children. We estimate the long-term (annual) average soil ingestion exposure distribution using daily soil ingestion estimates from children who participated in a mass-balance study at Anaconda, MT. The estimated distribution is accompanied by uncertainty estimates. The estimates take advantage of developing knowledge about bias in soil ingestion estimates and are robust. The estimates account for small particle size soil, use the median trace element estimate for subject days, account for the small sample variance of the median estimates, and use best linear unbiased predictors to estimate the cumulative long term soil ingestion distribution. Bootstrapping is used to estimate the uncertainty of the distribution estimates. The median soil ingestion is estimated as 24?mg/d (sd = 4?mg/d), with the 95 percentile soil ingestion estimated as 91?mg/d (sd = 16.6?mg/d). Strategies are discussed for use of these estimates in Monte Carlo risk assessment.     

Genome-Wide Association Studies and Heritability Estimates of Body Mass Index Related Phenotypes in Bangladeshi Adults

Many health outcomes are influenced by a person''s body mass index, as well as by the trajectory of body mass index through a lifetime. Although previous research has established that body mass index related traits are influenced by genetics, the relationship between these traits and genetics has not been well characterized in people of South Asian ancestry. To begin to characterize this relationship, we analyzed the association between common genetic variation and five phenotypes related to body mass index in a population-based sample of 5,354 Bangladeshi adults. We discovered a significant association between SNV rs347313 (intron of NOS1AP) and change in body mass index in women over two years. In a linear mixed-model, the G allele was associated with an increase of 0.25 kg/m² in body mass index over two years (p-value of 2.3·10⁻⁸). We also estimated the heritability of these phenotypes from our genotype data. We found significant estimates of heritability for all of the body mass index-related phenotypes. Our study evaluated the genetic determinants of body mass index related phenotypes for the first time in South Asians. The results suggest that these phenotypes are heritable and some of this heritability is driven by variation that differs from those previously reported. We also provide evidence that the genetic etiology of body mass index related traits may differ by ancestry, sex, and environment, and consequently that these factors should be considered when assessing the genetic determinants of the risk of body mass index-related disease.     

A Simple Determination Method for Herbicides,NIP and CNP in Soil Using Single Ion Monitoring Mass Spectrometry

A purified extracellular endo β-1,3-xylanase (EC 3.2.1.32) from an isolated strain, Aspergillus terreus A-07, was found to hydrolyze 1,3-xylosyl linkages only. When rhodymenan (β-1,4 and β-1.3-linked xylan) was hydrolyzed by β-1,3-xylanase (EF-6), four β-1,4-linked xylooligosaccharide fractions were produced. The main product was β-1,4-xylotriose, with trace amounts of other β-1,4-linked xylooligosaccharides. Successive degradation by β-l,4-xylosidase of the β,4-xylooligosaccharides that were produced from hydrolysis of β-1,3-xylanase on rhodymenan yielded only xylose as the final product.

We compared the action pattern of this enzyme with that of an extracellular endo β-l,4-xylanase (EC 3.2.1.8) of Streptomyces. From a mixture of products of β-1,4-xylanase hydrolysis on rhodymenan, an isomeric xylotriose was isolated by charcoal chromatography after treating with β-1.4-xylosidase. The structure of this isomeric xylotriose was elucidated by methylation analysis and its susceptibility to β-1,4-xylanase, β-1,3-xylanase, and β-1,4-xylosidase. The obtained isomeric xylotriose was identified as 3-O-β-xylopyranosyl-4-O-β-D-xylopyranosyl-D-xylose (X1→3X1→4X). It has a melting point of 224~225°C and ${\left[\alpha \right]}_{\text{D}}^{20}$(c = 1, H₂O)= —46°.     

Simple Methods of Determining Confidence Intervals for Functions of Estimates in Published Results

Often, the reader of a published paper is interested in a comparison of parameters that has not been presented. It is not possible to make inferences beyond point estimation since the standard error for the contrast of the estimated parameters depends upon the (unreported) correlation. This study explores approaches to obtain valid confidence intervals when the correlation is unknown. We illustrate three proposed approaches using data from the National Health Interview Survey. The three approaches include the Bonferroni method and the standard confidence interval assuming (most conservative) or (when the correlation is known to be non-negative). The Bonferroni approach is found to be the most conservative. For the difference in two estimated parameter, the standard confidence interval assuming yields a 95% confidence interval that is approximately 12.5% narrower than the Bonferroni confidence interval; when the correlation is known to be positive, the standard 95% confidence interval assuming is approximately 38% narrower than the Bonferroni. In summary, this article demonstrates simple methods to determine confidence intervals for unreported comparisons. We suggest use of the standard confidence interval assuming if no information is available or if the correlation is known to be non-negative.     

Adjusting for Heritable Covariates Can Bias Effect Estimates in Genome-Wide Association Studies

In recent years, a number of large-scale genome-wide association studies have been published for human traits adjusted for other correlated traits with a genetic basis. In most studies, the motivation for such an adjustment is to discover genetic variants associated with the primary outcome independently of the correlated trait. In this report, we contend that this objective is fulfilled when the tested variants have no effect on the covariate or when the correlation between the covariate and the outcome is fully explained by a direct effect of the covariate on the outcome. For all other scenarios, an unintended bias is introduced with respect to the primary outcome as a result of the adjustment, and this bias might lead to false positives. Here, we illustrate this point by providing examples from published genome-wide association studies, including large meta-analysis of waist-to-hip ratio and waist circumference adjusted for body mass index (BMI), where genetic effects might be biased as a result of adjustment for body mass index. Using both theory and simulations, we explore this phenomenon in detail and discuss the ramifications for future genome-wide association studies of correlated traits and diseases.     

A Simple Holder for Efficient Mass Staining of Thin Sections for Electron Microscopy

An inexpensive simply-constructed gridholder for reproducible staining of sections and storage of grids is made of a platelet of dental wax (Ladd No. 2460, or Belladi, rosa, normal) mounted on a glass slide. The grids are simply inserted perpendicularly into the wax and are held securely at their edges by the slightly sticky wax. Staining solutions may be applied directly to the standing grids or the gridholder may be inverted in a trough containing the staining solution, thus avoiding excessive contact with the air. Washing is carried out by dipping the gridholder in a series of beakers with distilled water or by flushing gently. The grids may be labeled directly on the slide and are therefore identified easily. The wax-gridholder eliminates excessive handling of the grids with tweezers not only during the staining procedure but as well as during storage and thus helps to prevent mechanical damage of the delicate sections mounted on the grids. Waxes other than those specified should not be used because of a tendency for particles to adhere to the grids, with the attendant possibility of column contamination.     

一种简便的DNA定量分子量标准的制备

目的：制备一种具有琼脂糖凝胶电泳定量功能的DNA分子量标准。方法：以pMD18-TSimple载体为基础骨架构建了长度为4.7kb的质粒,应用定点突变的方法,在载体上分别间隔100bp、200bp、400bp、800bp、1200bp处,加入了HindⅢ限制性内切酶的酶切位点,将该质粒扩增后并应用HindⅢ酶切后,1.5%琼脂糖凝胶电泳鉴定。结果：获得的分子量条带大小依次为100bp、200bp、400bp、800bp、1200bp和2000bp,每次使用4μl可获得质量范围为10ng、20ng、40ng、80ng、120ng和200ng的定量标准品。结论：应用该方法制备标准品,具有制备简单、成本低、定量快速等优点。     

Alpharadiography: A Simple Method for Determination of Mass Concentration in Cells and Tissues

A simple apparatus for the production of contact microradiographs with the help of a polonium alpha source and nuclear emulsion plates is described. This apparatus best adapted for soft tissue and low grade mineralization studies offers advantages as to resolution, geometry of specimen as well as ease of operation and cost.     

Effect of H. pylori Infection on Cytokine Profiles and Oxidative Balance in Subjects with Chronic Alcohol Ingestion

Different amounts of ingested alcohol can have distinct effects on the human body. However, there is limited research on chronic alcohol consumption with Helicobacter pylori infection. We sought to investigate the relationship between the cytokine profile, oxidative balance and H. pylori infection in subjects with chronic alcohol consumption. A total of 142 subjects were divided into three groups: 59 subjects with chronic alcohol ingestion and H. pylori infection (group A); 53 subjects with chronic alcohol ingestion without H. pylori infection (group B); and 30 control subjects (group C). The serum levels of CagA, interleukin (IL)-10, E-selectin, TNF-α, malondialdehyde (MDA) and superoxide dismutase (SOD) activity were measured by enzyme-linked immunosorbent assay (ELISA). We found that the ages and serum H. pylori CagA levels among the three groups, as well as both the mean drinking age and the mean daily alcohol consumption between groups A and B, were matched and comparable. Comparing the BMIs among the three groups, the BMI differences were found to be statistically significant (F=3.921, P<0.05). Compared with group C, the BMIs in groups A and B were significantly higher (P<0.001 and P<0.01, respectively); however, the BMI differences between group A and group B were not statistically significant (P>0.05). Additionally, no differences in the serum CagA levels were found in comparisons among the groups (all P>0.05). The serum IL-10 and E-selectin levels in group A were significantly lower than those in group B (serum IL-10: P<0.05; E-selectin: P<0.05). The serum IL-10 in group A was significantly higher than that in group C (P<0.01); the serum E-selectin levels in group A did not significantly differ compared with those in group C (P>0.05). Furthermore, the serum IL-10 and E-selectin levels in group B were significantly higher than those in group C (serum IL-10: P<0.001; E-selectin: P<0.05); however, the serum TNF-α levels did not differ among groups (all P>0.05). Although the serum levels of MDA and SOD in groups A and B were slightly lower than those in group C, there were no significant differences among groups (all P>0.05). In conclusion, we believe that H. pylori infection might cause a significant inhibition of certain cytokine profiles in subjects with chronic alcohol ingestion. Moreover, chronically ingested alcohol may exert an adjusted inflammatory effect, but there was no association between H. pylori infection, chronic alcohol consumption and oxidative balance.     

A Screening Level Mass Balance Model of Sediment Remediation Options

It is suggested that dynamic mass balance models can provide valuable support information when sediment remediation activities, such as dredging, are contemplated. A model with sufficient credibility and accuracy can be used to compare and contrast the results of various remediation actions and the effect of natural remediation processes. A food web model can also be included. The information provided by the model can be summarized in periodic (e.g. annual) “Report Cards” documenting the status of the contaminated system during and after the remediation process. Time plots of relevant properties of the system, such as contaminant masses, concentrations and levels in water, sediment and biota, can convey the essential information required for decision-making. This approach is illustrated by applying it with screening level accuracy to the remediation activities currently being undertaken in the St. Clair River, which flows from Lake Huron to Lake St. Clair near Sarnia, Ontario, Canada. The effects of dredging to reduce concentrations of hexachlorobenzene in sediment, water and biota are explored.