Relative cancer risks of chemical contaminants in the great lakes

Anyone who drinks water or eats fish from the Great Lakes consumes potentially carcinogenic chemicals. In choosing how to respond to such pollution, it is important to put the risks these contaminants pose in perspective. Based on recent measurements of carcinogens in Great Lakes fish and water, calculations of lifetime risks of cancer indicate that consumers of sport fish face cancer risks from Great Lakes contaminants that are several orders of magnitude higher than the risks posed by drinking Great Lakes water. But drinking urban groundwater and breathing urban air may be as hazardous as frequent consumption of sport fish from the Great Lakes. Making such comparisons is difficult because of variation in types and quality of information available and in the methods for estimating risk. Much uncertainty pervades the risk assessment process in such areas as estimating carcinogenic potency and human exposure to contaminants. If risk assessment is to be made more useful, it is important to quantify this uncertainty.     

Snowblower injuries in Vermont, 1981–1984

The Vermont Department of Health carried out two studies of snowblower injuries in Vermont during the winters of 1982–1983 and 1983–1984. The first was a case-control study in which we assessed risk factors that predisposed operators to injury during snowblower use. We found 20 persons who had been injured by snowblowers and matched 28 controls to these by neighborhood. In this study, owning a snowblower for 1 year or less and having operated a snowblower for 10 days or less in one's lifetime were significantly associated with injury. The second study was population-based. We estimated that approximately 1.5% of Vermont residents owned snowblowers during the winter of 1982–1983 and that, among snowblower owners, injuries occurred at a rate of 1.3/1,000 person-years of ownership (0.1% chance of injury).     

GROUNDWATER QUALITY IN THE CORTARO AREA NORTHWEST OF TUCSON,ARIZONA1

ABSTRACT The Cortaro Area is currently the depository for much of the liquid waste from the City of Tucson. In the past, more than one-half of the sewage effluent was used for crop irrigation. However, since 1970 virtually all of the sewage effluent has been percolated in the normally dry Santa Cruz River channel. Nitrate and chloride contents were monitored monthly in water samples from about 20 large-capacity irrigation wells. Contents and seasonal trends for these constituents were closely related to the disposal of sewage effluent. Water quality problems other than nitrate include total dissolved solids, boron, coliform, and lead. High lead contents in the area appear to be a natural phenomenon and the coliform contents are likely related to poor well construction. The other quality problems are primarily due to sewage effluent.     

Soil vapor extraction system design: A case study comparing vacuum and pore‐gas velocity cutoff criteria

Soil vapor extraction (SVE) systems are typically designed based on the results of a vadose‐zone pumping test (transient or steady‐state) using a pressure criterion to establish the zone of influence (ZOI). A common problem associated with pressure‐based SVE design is overestimating the ZOI of the extraction well. As a result, design strategies based upon critical pore‐ gas velocity (CPGV) have become more common. Field tests were conducted at the Savannah River Site (SRS) to determine the influence of a vapor extraction well based upon both a pressure and pore‐ gas velocity design criterion. The results from these tests show that an SVE system designed based upon a CPGV is more robust and will have shorter cleanup times due to increased flow throughout the treatment zone. Pressure‐based SVE design may be appropriate in applications where soil gas containment is the primary objective; however, in cases where the capture and removal of contaminated soil gas is the primary objective, CPGV is a better design criterion. © 2006 Wiley Periodicals, Inc.     

Impacts of land use conversion on bankfull discharge and mass wasting

Mass wasting and channel incision are widespread in the Nemadji River watershed of eastern Minnesota and northwestern Wisconsin. While much of this is a natural response to glacial rebound, sediment coring and tree ring data suggest that land use has also influenced these erosional processes. We characterized land use, inventoried mass wasting, surveyed stream channels and collected discharge data along segments of five streams in the Nemadji River watershed. Due to natural relief in this region, wetlands and agricultural lands are concentrated in the flatter terrain of the uplands of the Nemadji watershed, while forestland (coniferous or deciduous) is concentrated in the deeply incised (50-200% slope) stream valleys. Bankfull discharge was higher where forests had been converted from coniferous to deciduous forests and where there were fewer wetlands. Mass wasting increased exponentially with bankfull flows. While mass wasting was not correlated with forest type conversion and agricultural land use, it was negatively dependent upon wetland extent in headwater areas. Interactions between the spatial distribution of land use and terrain obfuscate any clear cause-and-effect relationships between land use, hydrology and fluvial processes.     

Case study approach to modeling historical disinfection by-product exposure in Iowa drinking waters

In the 1980 s, a case–control epidemiologic study was conducted in Iowa(USA) to analyze the association between exposure to disinfection by-products(DBPs) and bladder cancer risk. Trihalomethanes(THMs), the most commonly measured and dominant class of DBPs in drinking water, served as a primary metric and surrogate for the full DBP mixture.Average THM exposure was calculated, based on rough estimates of past levels in Iowa. To reduce misclassification, a follow-up study was undertaken to improve estimates of past THM levels and to re-evaluate their association with cancer risk. In addition, the risk associated with haloacetic acids, another class of DBPs, was examined. In the original analysis, surface water treatment plants were assigned one of two possible THM levels depending on the point of chlorination. The re-assessment considered each utility treating surface or groundwater on a case-by-case basis. Multiple treatment/disinfection scenarios and water quality parameters were considered with actual DBP measurements to develop estimates of past levels. The highest annual average THM level in the re-analysis was156 μg/L compared to 74 μg/L for the original analysis. This allowed the analysis of subjects exposed at higher levels( 96 μg/L). The re-analysis established a new approach, based on case studies and an understanding of the water quality and operational parameters that impact DBP formation, for determining historical exposure.     

THE FOREST–HYDROLOGY–POVERTY NEXUS IN CENTRAL AMERICA: AN HEURISTIC ANALYSIS

A ‘forest–hydrology–poverty nexus’ hypothesis asserts that deforestation in poor upland areas simultaneously threatens biodiversity and increases the incidence of flooding, sedimentation and other damaging hydrological processes. This paper uses rough heuristics to assess the applicability of this hypothesis to two montane forested countries in Central America: Guatemala and Honduras. We do so by using simple rules of thumb to identify watersheds at greater risk of hydrologically significant land use change, using information about land cover, slope, and watershed size. The location of these watersheds is compared to spatial maps of poverty and forests. We find plausible evidence for a forest–biodiversity–poverty connection in Guatemala, and to a lesser extent in Honduras.