First-trimester amniotic fluid and extraembryonic coelomic fluid acetylcholinesterase electrophoresis

Acetylcholinesterase (AChE) gel electrophoresis was performed on samples of amniotic fluid and extraembryonic coelomic fluid obtained by high resolution transvaginal ultrasound-guided amniocentesis from 38 women between 8 and 12 weeks of pregnancy. AChE was positive in 33 per cent (12/36) of the amniotic fluid samples; the percentage of positive results decreased as gestation advanced. AChE was positive in 32 per cent (9/28) of the extraembryonic coelomic fluid samples. In 81 per cent (21/26) of matched samples, the AChE results were identical in the two fluids. Amniotic fluid and extraembryonic coelomic fluid AChE electrophoresis cannot be used to diagnose neural tube defects prior to 12 weeks of gestation.     

Polyzyklische aromatische Kohlenwasserstoffe aus diffusen Quellen

Goal and Scope

Polycyclic aromatic hydrocarbons (PAHs) are one group of persistent organic pollutants which are ubiquitous distributed in soils, even in rural areas. After their release into the atmosphere, transportation and deposition, they tend to accumulate in topsoils and sediments. Similar distribution pattern of PAHs in atmospheric deposition, soil samples as well as sediment samples indicate a close relationship between atmospheric input and accumulation of PAHs in the terrestrial environment. The intention of this paper was to estimate the time when precautionary values of the German law of soil protection will be exceeded in rural areas. Furthermore, current soil concentrations will be linked to the historical record of PAHs by means of enrichment factors.

Methods

The historical record of the atmospheric deposition rates of PAHs can be obtained from investigation of sediment cores. Based thereon, enrichment factors of PAHs in the environment were calculated. With these enrichment factors it was possible to estimate the recent PAH concentration in soils in rural areas from currently measured annual deposition rates. Furthermore, concentrations of PAHs in soils and deposition rates can be used to calculate the time when precautionary values will be reached.

Results and Conclusion

PAH deposition rates have been decreasing since about 1960 by a factor of 2–3, but stabilized during the last decade on a level high above pre-industrial time. Thus, further enrichment of PAH in topsoils has to be expected. Actual deposition rates in connection with historical enrichment factors allow to determine the median concentrations of PAHs in rural soils. The time when precautionary values will be reached was calculated to about 300 Years.

Outlook

The database to predict the further development of atmospheric deposition rates is very weak. There was a lack of validated methods concerning direct measurements of atmospheric POP deposition. Meanwhile, a national draft of a standard base on time-integrated passive sampling exists. This method can be implemented to establish a combined soil and deposition-monitoring program in order to assess the risk of further accumulation of POPs in soils.     

Evaluation of the validity of the US EPA's cancer risk assessment of arsenic for low-level exposures: a likelihood ratio approach

Skin cancers associated with ingesting of arsenic have been documented since the 19th century. A study in the southwestern coastal area of Taiwan where people drank well water containing arsenic is generally recognised as providing the best data available for quantifying the risk, and the US Environmental Protection Agency (EPA) used these data to conduct a risk assessment of arsenic ingestion. However, the lowest exposure category in the Taiwan study included arsenic levels up to 290 µg L^–1, which is nearly six times higher than the current EPA maximum contaminant level (MCL), 50 µg L^–1. Therefore, the EPA risk assessment model extrapolated data on high-level exposures to generate risk estimates for low-level exposures. To evaluate the validity of this model, we conducted a quantitative review of epidemiological studies observing arsenic exposures below 290 µg L^–1. A ratio of the likelihood of the EPA model being inappropriate to that of it being appropriate was calculated for each study population as a measurement of the validity of the EPA model. Although existing human data on low-level exposures are limited, the review suggested that the EPA model is unlikely to be able to predict the risk of skin cancer accurately when the arsenic exposure level is between 170 and 270 µg L^–1.     

Geophagy in the tropics: an appraisal of three geophagical materials

Geophagy, the deliberate consumption of soil, is a common practice amongst the world's poorer or more tribally oriented people of the tropics. An appraisal of three geophagical samples suggests that Fe is a mineral nutrient which can be supplied to humans in significant amounts via ingested soil. Geophagy provides a direct link between the geochemistry of soils and human health, but as yet this association has only a limited awareness amongst research workers.     

Conservation Implications of the Natural Loss of Lineages in Wild Mammals and Birds

Because populations in zoological parks and nature reserves often are derived from only a few individuals, conservationists have attempted to minimize founder effects by equalizing family group sizes and increasing the reproductive contributions of all individuals. Although such programs reduce potential losses of genetic diversity, information is rarely available about the actual persistence of family groups or genetic lineages in natural populations. In the absence of such data, it can be difficult to weigh the importance of human intervention in the conservation of small populations. Separate long-term studies of two mammals, the North American bison (Bison bison) and the white-nosed coati (Nasua narica), and a bird, the Acorn Woodpecker (Melanerpes formicivorus), demonstrate differential extinction of genetic lineages. Irrespective of the mechanisms affecting population structure, which may range from stochastic environmental events to such behavioral phenomena as poor intrasexual competitive abilities, our results show that lineages can be lost at rapid rates from natural populations. A survey of comparable studies from the literature indicates that the loss of matrilines over the course of the study varies from 3% to 87% in wild mammals and from 30% to 80% in birds, with several small mammals losing approximately 20% of matrilines per year of study. These lineage extinctions were not an artifact of the length of the study or the generation time of the species. Such rapid losses of lineages in less than 20-year periods in natural populations suggest that efforts to maintain maximal genetic diversity within populations may not always reflect processes that occur in the wild. Conservation biologists need to give further thought to the extent to which parity among genetic lines should be a primary goal of management of captive and small wild populations.