Schadstoffbelastung durch Persorption von Bodenpartikeln

The term persorption describes the paracellular uptake of particles from the digestive tract. It has been shown that solid, hard microparticles such as starch granules, cellulose particles, fibres and crystals are incorporated from the digestive tract. It is likely that an uptake of soil contaminants may also occur via this mechanism, thereby increasing the health risks of children through soil ingestion. The aim of this study was to evaluate the significance of such soil contaminant absorption via this mechanism using data from the literature. Since no information was available on the persorption of soil particles, studies using other models had to be evaluated. The results of these studies show that a persorption of soil particles must be expected. The maximum persorption rate occurs for diameters of <35 μm which is in the range of diameters of street dust, clay and coarse clay. The persorption of these particles is therefore of significance. Data from the literature, however, does not allow an estimation of the magnitude of persorption of such soil particles. Basically, it is conceivable that a relevant ingestion of less mobile pollutants is possible through their persorption in the gastrointestinal tract. Aside from an increased internal exposure via the persorption of soil particles carrying contaminants, additional health risks may occur through the long-term deposit of such particles, the presence of potential allergens as well as through the embolisation of small vessels.     

Application of an improved method for the analysis of pesticides and their metabolites in the urine of farmer applicators and their families

As the annual use of pesticides in the United States has escalated, public health agencies have become increasingly concerned about chronic pesticide exposure. However, without reliable, accurate analytical methods for biological monitoring, low-level chronic exposures are often difficult to assess. A method for measuring simultaneously the urinary residues of as many as 20 pesticides has been significantly improved. The method uses a sample preparation which includes enzyme digestion, extraction, and chemical derivatization of the analytes. The derivatized analytes are measured by using gas chromatography coupled with isotope-dilution tandem mass spectrometry. The limits of detection of the modified method are in the high pg/L - low μg/L range, and the average coefficient of variation (CV) of the method was below 20% for most analytes, with approximately 100% accuracy in quantification. This method was used to measure the internal doses of pesticides among selected farmer applicators and their families. Definite exposure and elimination patterns (i.e., an increase in urinary analyte levels following application and then a gradual decrease to background levels) were observed among the farmer applicators and many of the family members whose crops were treated with carbaryl, dicamba, and 2,4-D esters and amines. Although the spouses of farm workers sometimes exhibited the same elimination pattern, the levels of the targeted pesticides or metabolites found in their urine were not outside the ranges found in the general U.S. population (reference range). The farmer applicators who applied the pesticides and some of their children appeared to have higher pesticide or metabolite levels in their urine than those found in the general U.S. population, but their levels were generally comparable to or lower than reported levels in other occupationally exposed individuals. These results, however, were obtained from a nonrandom sampling of farm residents specifically targeted to particular exposures who may have altered their practices because they were being observed; therefore, further study is required to determine if these results are representative of pesticide levels among residents on all farms where these pesticides are applied using the same application techniques. Using this method to measure exposure in a small nonrandom farm population allowed differentiation between overt and background exposure. In addition, the important role of reference-range information in distinguishing between various levels of environmental exposure was reaffirmed.     

Female oviposition-site preference and egg hatching success in the damselfly Calopteryx splendens xanthostoma

By removing males and controlling the rate of water flow past oviposition patches in an experimental area, we showed that female Calopteryx splendens xanthostoma preferred to oviposit in fast flowing water rather than slow flowing water. A series of manipulations revealed the fitness benefits to females for this preference: eggs placed in fast-flowing water developed significantly faster and showed significantly lower mortality than eggs placed in slow-flowing water. A major factor determining this difference was the deposition and growth of encrusting algae which prevented the successful hatching of eggs in slow-flowing water.     

Experimental research on race and sex discrimination: The record and the prospects

Research in industry regarding race and sex access discrimination is reviewed. Review of sex discrimination research suggests that negative access discrimination exists for female applicants when the position is male-stereotyped and positive access discrimination exists when it is female-stereotyped. Results on race discrimination are few in number with mixed results, some showing reverse discrimination and others showing discrimination against blacks. More complex studies examining interactions between race and sex also provide mixed results. Recent evidence, which suggests that selection decisions are much more complex than have been studied, may account for the conflicting findings. Future research with more imaginative and complex designs and larger sample sizes is needed. Research designs should be selected to facilitate better measurement of the effects of civil rights law enforcement.