Nuckols et al. 2011 Flashcards
Three disciplines using GIS in exposure assessment
- Geospatial science
- Environmental science
- Epidemiology
Geospatial science
Systematic study of geographic variables relating to, occupying, or having the character of space
Raster model
Grid cells serve as basic units of analysis
Vector model
Uses points, lines, or polygons based on continuous geometry of space to represent data
Triangulated irregular network model
Representing elevation data often used for terrain analysis
Cartigraphic scale
Traditional map scale ratio
Relates the size of feature in life to size on map
Geographic extent
Size of study area
Different results based on study area (rate of caner in county vs. province)
Spatial resolution
Grain or smallest unit distinguishable
Map data at different scales will allow for resolution of different objects
Resolution is chosen based on whats needed
Operational scale
Scale at which process of interest occurs
Can be resolution dependent (detected at one scale but not another)
Accuracy
How well GIS data represents reality in terms of positional, attribute and temporal accuracy
Positional accuracy
Agreement between data representation in GIS and actual location of data on ground (ground truth)
Attribute accuracy
Measure of how well information linked to the data representation format is correct
Temporal accuracy
Appropriateness of using particular snapshot or snapshots of time for GIS analysis or modelling effort
Errors in GIS
Source errors: accuracy of data (differences between data and reality)
Processing errors: introduced into database resulting from GIS-based analysis and modelling
Environmental science
Systematic study of the complex physical, chemical and biotic factors that act upon an organism or ecologic community and ultimately determine its form and survival
Stochastic simulation data
To supplement measurement data
Based on statistical probability
Deterministic simulation data
To supplement measurement data
Based on physical processes
Geophysical plausibility
Application of environmental science to exposure assessment for epidemiology
Association between contaminant source and exposure cannot exist unless there is a plausible geophysical route of transport between source and receptor
Berkson errors
Errors in classifying exposure
Exposure metric is at population level and individual exposures vary because of different activity patterns
Classical error model
Errors in classifying exposure
Exposure metric used in study is measured with error and is imperfect surrogate for true exposure
Sensitivity
Ability of exposure metric to correctly classify as exposed those who are truly exposed
Specificity
Ability of exposure metric to correctly classify as unexposed those who are unexposed
Source identification
Function of the occurrence of the target agent in a specified environmental medium
Allows assessment of likelihood of exposure across study population and route of exposure data needed to calculate personal exposure
MODFLOW
Simulation model which accurately reflected hydraulic characteristics of ground water regime in area
Exposure
Contact of physical, chemical or biological agent with outer boundary of organism
Function of concentration and time
Environmental concentration
Agents presence in a particular carrier medium, expressed in quantitative terms
Exposure concentration
Agents presence in its carrier medium at point of contact
Dose
Amount of pollutant that actually enters human body
GPS
Satellite-based technology composed of a system of satellites encircling earth and emitting radio frequency detectable by receivers
Environmental epidemiology
Areas of epidemiology concerned with the study of associations between environmental exposures and health outcomes
Steps in exposure assessment process (4)
1) Define study population
2) Identify source and potential routes of exposure
3) Estimating environmental levels of target contaminants
4) Estimating personal exposures
Validation
Validate with environmental measures and transport modelling
