Asbestos in potable water

Several published reports indicate that asbestos is found in public drinking water supplies. In order to determine the health effects of ingested asbestos, relevant animal and human studies were reviewed. From these studies, it was not possible to predict potential health hazards associated with ingestion of the levels of asbestos found in drinking water. Detailed examinations of Water samples were carried out by electron microscopy in order to determine the precision of analysis for waterborne asbestos. Asbestos-cement pipes, used to transmit drinking water, were studied under field conditions. No significant release of asbestos was observed. Preliminary work suggests that asbestos is present in Lake Michigan. An investigation of possible sources of asbestos into Lake Michigan indicated that wet deposition of asbestos may be a principal pathway of asbestos contamination of Lake Michigan. A feasibility study was carried out to determine if asbestos is present in rainwater collected in the Chicago area. Chrysotile asbestos was found in Chicago rainwater at a level of 10⁵ to 10⁶ fibers per liter. This finding demonstrates that precipitation scavenges airborne chrysotile asbestos which may result in the contamination of surface waters.U.S. Department of the InteriorU.S. Geological SurveyOpe

Relationship between high sodium levels in municipally softened drinking water and elevated blood pressure

A recent study in Massachusetts found that a group of high school sophomores exposed to 107 mg/l sodium in their drinking water had significantly higher blood pressures than a control group exposed to a lower level of sodium (8 mg/l). The present study was undertaken in Illinois to determine if these findings could be repeated with a group of high school juniors and seniors from two communities, LaGrange and Westchester, located in the Chicago metropolitan area. The concentration of sodium in LaGrange's municipal drinking water is 405 mg/l as compared to 4 mg/l for Westchester. Of the 386 eligible students in LaGrangeI.84%volunteered to have their blood pressures taken. In Westchester, 78% of the 401 eligible students volunteered. Results of the survey indicated that male and female systolic blood pressures in the high sodium community were not higher than those in the low-sodium community (p > 0.05). In contrast, the male and female diastolic blood pressures were significantly higher in the high-sodium community (p < 0.05). However, the increases in diastolic blood pressures were not as large as those observed in the Massachusetts study. The long-term significance of these findings is unknown. However, they do indicate a need for further follow-up study to determine if there is an association with the development of hypertension.U.S. Department of the InteriorU.S. Geological SurveyOpe

Signatures of arithmetic simplicity in metabolic network architecture

Metabolic networks perform some of the most fundamental functions in living cells, including energy transduction and building block biosynthesis. While these are the best characterized networks in living systems, understanding their evolutionary history and complex wiring constitutes one of the most fascinating open questions in biology, intimately related to the enigma of life's origin itself. Is the evolution of metabolism subject to general principles, beyond the unpredictable accumulation of multiple historical accidents? Here we search for such principles by applying to an artificial chemical universe some of the methodologies developed for the study of genome scale models of cellular metabolism. In particular, we use metabolic flux constraint-based models to exhaustively search for artificial chemistry pathways that can optimally perform an array of elementary metabolic functions. Despite the simplicity of the model employed, we find that the ensuing pathways display a surprisingly rich set of properties, including the existence of autocatalytic cycles and hierarchical modules, the appearance of universally preferable metabolites and reactions, and a logarithmic trend of pathway length as a function of input/output molecule size. Some of these properties can be derived analytically, borrowing methods previously used in cryptography. In addition, by mapping biochemical networks onto a simplified carbon atom reaction backbone, we find that several of the properties predicted by the artificial chemistry model hold for real metabolic networks. These findings suggest that optimality principles and arithmetic simplicity might lie beneath some aspects of biochemical complexity