Recent aspects of uranium toxicology in medical geology.

Uranium (U) is a chemo-toxic, radiotoxic and even a carcinogenic element. Due to its radioactivity, the effects of U on humans health have been extensively investigated. Prolonged U exposure may cause kidney disease and cancer. The geological distribution of U radionuclides is still a great concern for human health. Uranium in groundwater, frequently used as drinking water, and general environmental pollution with U raise concerns about the potential public health problem in several areas of Asia. The particular paleo-geological hallmark of India and other Southern Asiatic regions enhances the risk of U pollution in rural and urban communities. This paper highlights different health and environmental aspects of U as well as uptake and intake. It discusses levels of U in soil and water and the related health issues. Also described are different issues of U pollution, such as U and fertilizers, occupational exposure in miners, use and hazards of U in weapons (depleted U), U and plutonium as catalysts in the reaction between DNA and H2O2, and recycling of U from groundwater to surface soils in irrigation. For use in medical geology and U research, large databases and data warehouses are currently available in Europe and the United States.

Metals in soils of children's urban environments in the small northern European city of Uppsala.

Metals occur naturally in soil, but contents are generally increased in the urban environment due to anthropogenic activities. The presence of elevated metals in soils of the urban environment has been recognized as an important source of metal intake in children and is linked to elevated metal levels in children's blood. Several metals have undesirable health effects, especially on children due to their still developing nervous system and small body volumes. Playgrounds are where urban children spend most of their time outdoors and are also where children most frequently come in contact with soil. Elevated contents of metals in playgrounds are therefore of great concern for children's wellbeing. This study investigates the soil metal content of 25 playgrounds located in different land use areas in urban Uppsala, Sweden's fourth largest city. Uppsala covers an area of approximately 100 km2 and has a population of 136,000. The soil samples were analysed for 12 metals (Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, W, Zn) using aqua regia. Median metal contents were found to be 1.8, 3.4, 0.21, 32, 25, 2.5, 0.14, 494, 19, 26, 0.35 and 84 mg kg(-1) soil for each of the above metals, respectively. The median clay content was around 20% while the organic matter content was measured by loss on ignition at a median of 8%. The land use areas included industrial land, the city center, road verges, natural land and former industrial land. The results showed that land use did not have the expected large influence on the total metal contents of the soils tested. The clay content together with the age of the site proved to be a more important factor. Sites with elevated clay contents had in general elevated metal contents, which were explained by the relatively high adsorption capacity of clay particles. The soils at sites where land use had not been altered since the 1800s had increased metal contents compared to playgrounds constructed in the late 1900s. The immobility of metals once they had entered the soil system was the reason for increased metal content in soils of old playgrounds. It was concluded that in cities with few internal pollution sources, the soil characteristics of the site and the time the soil has been on-site to accumulate metal residues become important factors in determining the soil metal content.

The emerging Medical and Geological Association.

The impact on human health by natural materials such as water, rocks, and minerals has been known for thousands of years but there have been few systematic, multidisciplinary studies on the relationship between geologic materials and processes and human health (the field of study commonly referred to as medical geology). In the past few years, however, there has been a resurgence of interest in medical geology. Geoscientists working with medical researchers and public health scientists have made important contributions to understanding novel exposure pathways and causes of a wide range of environmental health problems such as: exposure to toxic levels of trace essential and non-essential elements such as arsenic and mercury; trace element deficiencies; exposure to natural dusts and to radioactivity; naturally occurring organic compounds in drinking water; volcanic emissions, etc. By linking with biomedical/public health researchers geoscientists are finally taking advantage of this age-old opportunity to help mitigate environmental health problems. The International Medical Geology Association has recently been formed to support this effort.

Comparison of two monitoring systems for Cu and Mo in the Swedish environment.

Bio-geochemical samples (BGS) are roots of certain aquatic plants and mosses suitable for monitoring elements dissolved in stream water. The moose, a wild ruminant living in most parts of Sweden, represents higher trophic level and another manifestation of bioavailability. By analyzing BGS (n approximately 33600) and moose liver (n approximately 2400), a systematic survey has been performed in the terrestrial environment of Sweden. Cu and Mo are essential elements for life, and their presence is especially important for the Cu-dependent processes in ruminants. The availability of Cu and Mo as monitored in BGS and moose was visualized in the form of maps and subjected to further statistical analysis. The medians, with lower and upper quartiles indicated as intervals, for the country as a whole were: moose liver, Cu = 34 (20-59), Mo = 0.82 (0.58-1.06) mg kg(-1) wet weight; BGS, Cu = 50 (35-77), Mo = 9.0 (5.3-18.0) mg kg(-1) dry weight. The ranges of medians for the 22 Swedish counties were: moose liver, Cu = (20-62), Mo = (0.54-1.18) mg kg(-1) wet weight; BGS, Cu = (28-115), Mo = (5-47) mg kg(-1) dry weight. The relationships between the counties and the connections between the monitoring variables were elucidated by principal component analysis (PCA). It was demonstrated that two monitoring systems could give divergent results. An unexpectedly strong negative correlation was found between the county medians for Cu in BGS and moose liver. A possible explanation, based on the interaction between Cu and Mo in moose, could not be verified.

Bioaccessibility of metals in urban playground soils.

Children ingest soil. The amount ingested varies with the child's behaviour, and daily ingestion rates have been calculated to be between 39 and 270 mg day(-1). During play, children ingest soil both involuntarily and deliberately, and it can be assumed that the latter may result in ingestion of a larger soil particle size fraction and a larger soil mass than the former. Measurements of soil metal contents commonly display the total metal content, where soil sieved to <2 mm has been digested with strong acids. This procedure does not consider differences in metal contents between size fractions or ingested soil masses. Moreover, it does not consider the difference between bioaccessible and total metal content, possibly resulting in an incorrect evaluation of the potential health risks from soil intake. Intervention and guideline values are commonly calculated via tolerable daily intake values, in turn derived from toxicological studies where the contaminant is administered to a test animal in feed or water. It is then assumed that the bioavailability of a contaminant in soil equals the bioavailability in the matrix used in the toxicology study. However, the complexity and heterogeneity of soil often results in a lower bioavailability than from food or water. The current study investigated the bioaccessibility of soil As, Cd, Cr, Ni and Pb from two different particle size fractions representing deliberate (<4 mm) and involuntary (<50 microm) ingestion, as well as from two different soil masses representing deliberate soil intake; 2 g for a child with pica behaviour and 0.6 g for a non-pica child. The bioaccessibility was investigated using an in vitro digestion model and urban playground soils collected away from any point pollution sources. The bioaccessibility (%) of the different metals increased in the order Ni=Cr=Pb<