National maps of the effects of particulate matter on mortality: exploring geographical variation.
(9/1285)
In this paper, we present national maps of relative rates of mortality associated with short-term exposure to particulate matter < 10 micro m in aerodynamic diameter (PM(10)). We report results for 88 of the largest metropolitan areas in the United States from 1987 to 1994 for all-cause mortality, combined cardiovascular and respiratory deaths, and other causes of mortality. Maximum likelihood estimates of the relative rate of mortality associated with PM(10)and the degree of statistical uncertainty were obtained for each of the 88 cities by fitting a separate log-linear regression of the daily mortality rate on air pollution level and potential confounders. We obtained Bayesian estimates of the relative rates by fitting a hierarchical model that takes into account spatial correlation among the true city-specific relative rates. We found that daily variations of PM(10) are positively associated with daily variations of mortality. In particular, the relative rate estimates of cardiovascular and respiratory mortality associated with PM(10) are larger on average than the relative rate estimates of all-cause and other-cause mortality. The estimated increase in the relative rate of death from cardiovascular and respiratory mortality, all-cause mortality, and other-cause mortality were 0.31% (95% posterior interval, 0.15-0.5), 0.22% (95% posterior interval, 0.1-0.38), and 0.13% (95% posterior interval, -0.05 to 0.29), respectively. Bayesian estimates of the city-specific relative rates ranged from 0.23% to 0.35% for cardiovascular and respiratory mortality, from 0.18% to 0.27% for all causes, and from 0.10% to 0.20% for other causes of mortality. The spatial characterization of effects across cities offers the potential to identify factors that could influence the effect of PM(10) on health, including particle characteristics, offering insights into mechanisms by which PM(10) causes adverse health effects. (+info)
Time-location analysis for exposure assessment studies of children using a novel global positioning system instrument.
(10/1285)
Global positioning system (GPS) technology is used widely for business and leisure activities and offers promise for human time-location studies to evaluate potential exposure to environmental contaminants. In this article we describe the development of a novel GPS instrument suitable for tracking the movements of young children. Eleven children in the Seattle area (2-8 years old) wore custom-designed data-logging GPS units integrated into clothing. Location data were transferred into geographic information systems software for map overlay, visualization, and tabular analysis. Data were grouped into five location categories (in vehicle, inside house, inside school, inside business, and outside) to determine time spent and percentage reception in each location. Additional experiments focused on spatial resolution, reception efficiency in typical environments, and sources of signal interference. Significant signal interference occurred only inside concrete/steel-frame buildings and inside a power substation. The GPS instruments provided adequate spatial resolution (typically about 2-3 m outdoors and 4-5 m indoors) to locate subjects within distinct microenvironments and distinguish a variety of human activities. Reception experiments showed that location could be tracked outside, proximal to buildings, and inside some buildings. Specific location information could identify movement in a single room inside a home, on a playground, or along a fence line. The instrument, worn in a vest or in bib overalls, was accepted by children and parents. Durability of the wiring was improved early in the study to correct breakage problems. The use of GPS technology offers a new level of accuracy for direct quantification of time-location activity patterns in exposure assessment studies. (+info)
A geographic information system for characterizing exposure to Agent Orange and other herbicides in Vietnam.
(11/1285)
Between 1961 and 1971, U.S. military forces dispersed more than 19 million gallons of phenoxy and other herbicidal agents in the Republic of Vietnam, including more than 12 million gallons of dioxin-contaminated Agent Orange, yet only comparatively limited epidemiologic and environmental research has been carried out on the distribution and health effects of this contamination. As part of a response to a National Academy of Sciences' request for development of exposure methodologies for carrying out epidemiologic research, a conceptual framework for estimating exposure opportunity to herbicides and a geographic information system (GIS) have been developed. The GIS is based on a relational database system that integrates extensive data resources on dispersal of herbicides (e.g., HERBS records of Ranch Hand aircraft flight paths, gallonage, and chemical agent), locations of military units and bases, dynamic movement of combat troops in Vietnam, and locations of civilian population centers. The GIS can provide a variety of proximity counts for exposure to 9,141 herbicide application missions. In addition, the GIS can be used to generate a quantitative exposure opportunity index that accounts for quantity of herbicide sprayed, distance, and environmental decay of a toxic factor such as dioxin, and is flexible enough to permit substitution of other mathematical exposure models by the user. The GIS thus provides a basis for estimation of herbicide exposure for use in large-scale epidemiologic studies. To facilitate widespread use of the GIS, a user-friendly software package was developed to permit researchers to assign exposure opportunity indexes to troops, locations, or individuals. (+info)
Investigation of an anthrax outbreak in Alberta in 1999 using a geographic information system.
(12/1285)
A Geographic Information System was used to document an anthrax outbreak in Alberta in 1999 and to describe the physical and environmental conditions of the area. The majority of infected farms were located on poorly drained organic soils. Regulatory agencies should consider adopting this tool for animal disease outbreak investigations. (+info)
Using geographic information systems to assess risk for elevated blood lead levels in children.
(13/1285)
OBJECTIVES: Targeted screening for childhood lead poisoning depends on assessment of risk factors including housing age. Using a geographic information system (GIS), we aim to determine high-risk regions in Charleston County, South Carolina, to assist public health officials in developing targeted lead-screening. METHODS: Properties built before 1978 were geocoded (assigned latitude and longitude coordinates) from tax assessor data. Addresses of Charleston County children who have been screened for lead poisoning were also geocoded. Locations of all housing, lead poisoning cases, and negative screens were created as separate map layers. Prevalence ratios of lead poisoning cases were calculated, as were relative risks for each category of housing. RESULTS: Maps of Charleston County were produced showing the location of old housing, where screening took place, and where cases were found. One thousand forty-four cases were identified. Twenty percent of children living in pre-1950 homes had elevated blood lead levels (EBLL). Children living in pre-1950 housing were 3.9 times more likely to have an EBLL than children living in post-1977 housing. There was no difference in risk of living in a 1950-1977 home vs. a post-1977 home. A large number of cases were also found in an area of newer houses, but near a potential point source. Eighty-two percent of all screens were from children in post-1977 homes. CONCLUSIONS: Children living in pre-1950 housing were at higher risk for lead poisoning. GIS is useful in identifying areas of risk and unexpected clustering from potential point sources and may be useful for public health officials in developing targeted screening programs. (+info)
Large-scale mapping and predictive modeling of submerged aquatic vegetation in a shallow eutrophic lake.
(14/1285)
A spatially intensive sampling program was developed for mapping the submerged aquatic vegetation (SAV) over an area of approximately 20,000 ha in a large, shallow lake in Florida, U.S. The sampling program integrates Geographic Information System (GIS) technology with traditional field sampling of SAV and has the capability of producing robust vegetation maps under a wide range of conditions, including high turbidity, variable depth (0 to 2 m), and variable sediment types. Based on sampling carried out in August-September 2000, we measured 1,050 to 4,300 ha of vascular SAV species and approximately 14,000 ha of the macroalga Chara spp. The results were similar to those reported in the early 1990s, when the last large-scale SAV sampling occurred. Occurrence of Chara was strongly associated with peat sediments, and maximal depths of occurrence varied between sediment types (mud, sand, rock, and peat). A simple model of Chara occurrence, based only on water depth, had an accuracy of 55%. It predicted occurrence of Chara over large areas where the plant actually was not found. A model based on sediment type and depth had an accuracy of 75% and produced a spatial map very similar to that based on observations. While this approach needs to be validated with independent data in order to test its general utility, we believe it may have application elsewhere. The simple modeling approach could serve as a coarse-scale tool for evaluating effects of water level management on Chara populations. (+info)
Assessment of land-use impact on macroinvertebrate communities in the Zwalm River basin (Flanders, Belgium) using multivariate analysis and geographic information systems.
(15/1285)
Relationships between land-use and river water quality assessed by means of biological and physical-chemical variables and habitat characteristics were analysed for the Zwalm River basin in Flanders (Belgium). The research focussed on three zones within this river basin, each characterized by different land uses, and consequently, different types of pollution, mainly of diffuse origin. Environmental data have been integrated within a Geographic Information System. Possible relationships between aquatic ecosystem and land-use variables were searched for by means of multivariate analysis. (+info)
The relationship between air pollution from heavy traffic and allergic sensitization, bronchial hyperresponsiveness, and respiratory symptoms in Dutch schoolchildren.
(16/1285)
Studies have suggested that children living close to busy roads may have impaired respiratory health. This study was designed to test the hypothesis that exposure to exhaust from heavy traffic in particular is related to childhood respiratory health. Children attending 24 schools located within 400 m from busy motorways were investigated. The motorways carried between 5,190 and 22,326 trucks per weekday and between 30,399 and 155,656 cars per day. Locations were chosen so that the correlation between truck and car traffic counts was low. Air pollution measurements were performed at the schools for 1 year. Respiratory symptoms were collected by parent-completed questionnaire. Sensitization to common allergens was measured by serum immunoglobulin E and skin prick tests. Bronchial hyperresponsiveness (BHR) was measured with a hypertonic saline challenge. Respiratory symptoms were increased near motorways with high truck but not high car traffic counts. They were also related to air pollutants that increased near motorways with high truck traffic counts. Lung function and BHR were not related to pollution. Sensitization to pollen increased in relation to truck but not car traffic counts. The relation between symptoms and measures of exposure to (truck) traffic-related air pollution were almost entirely restricted to children with BHR and/or sensitization to common allergens, indicating that these are a sensitive subgroup among all children for these effects. (+info)