Research
Arsenic Presentations
4/2005, AvRuskin et al. Association of American Geographers. Individual exposure reconstruction using a time geographic approach.
4/2005, Jacquez et al. Association of American Geographers. Case-control clustering for residential histories.
10/2004, Meliker et al., International
Society for Exposure Analysis
Generating Continuous Exposure Estimates over the
Life Course: Applications of a Space Time Information
System
11/2004, Slotnick et al., American Public Health Association
Improving exposure assessment in environmental
epidemiology: Application of a Space-Time
Information System (STIS) to assess arsenic exposure
in drinking water
11/2004 AvRuskin et al. GIScience 2004
Creating a
Space Time Information System to Investigate
Arsenic Exposure in Drinking Water.
Individual exposure reconstruction using a time geographic approach
Gillian Avruskin1, Geoffrey Jacquez1, PhD, Andrew Kaufmann1, MS, Jaymie Meliker2, MS
1 BioMedware, Inc., 516 North State Street, Ann Arbor, MI 48104
2 Environmental Health Sciences, University of Michigan School of Public Health, 109 S. Observatory, SPH-I, Ann Arbor, MI 48109.
Researchers in environmental health and epidemiology have recently become interested in spatial temporal relationships to investigate individual exposure over time to environmental contaminants. Inclusion of spatial data through the use of Geographic Information Systems (GIS) is enhancing exposure reconstruction in environmental epidemiology; however, it inadequately characterizes temporal changes and their impact on exposure reconstruction. Here, we extend Hagerstrand’s time geographic perspective to reconstruct individual exposure to environmental contaminants. The space time path presents a foundation on which an individual’s exposure history can be reconstructed. Looking at all the places an individual has lived and for how long provides a simple account of an individual’s exposure. This approach can be extended to include a more in depth aspect of exposure reconstruction by developing ‘exposure constraints’ and ‘exposure prisms’, similar in theory to the constraints and space time prisms of Hagerstrand. Investigating these ‘exposure histories’ as space time paths is an innovative method that researchers in environmental health sciences will find useful. Preliminary results of the exposure reconstruction will be presented using data from a case control study of bladder cancer in Michigan. It is expected that the time geographic approach to exposure reconstruction will constitute a valuable tool for validating and supplementing traditional tools of exposure reconstruction.
Case-control clustering for residential histories
Geoffrey Jacquez1, PhD, Andrew Kaufmann1, MS, Jaymie Meliker2, MS, Pierre Goovaerts1, PhD, Gillian Avruskin1, MS, Jerome Nriagu2, PhD.
1 BioMedware, Inc., 516 North State Street, Ann Arbor, MI 48104
2 Environmental Health Sciences, University of Michigan School of Public Health, 109 S. Observatory, SPH-I, Ann Arbor, MI 48109.
This paper introduces a new approach for evaluating clustering in case-control data that accounts for residential histories. Although many statistics have been proposed for assessing local, focused and global clustering in health outcomes, few, if any, exist for evaluating clusters when individuals are mobile. In this paper local, global and focused tests for residential histories are developed based on sets of matrices of nearest neighbor relationships that reflect the changing topology of cases and controls. Exposure traces are defined that account for the latency between exposure and disease manifestation, and that use exposure windows of varying duration. Several of the methods so derived are applied to evaluate clustering of residential histories in a case-control study of bladder cancer in south eastern Michigan. Because humans are mobile, the methods proposed in this paper are preferred over traditional approaches that assume sessile individuals.
Generating Continuous Exposure Estimates over the Life Course: Applications of a Space Time Information System
Jaymie Meliker1, MS, Melissa J. Slotnick1, MPH, MESc, Jerome Nriagu1, PhD., Gillian Avruskin2, MS, Andrew Kaufmann2, MS, Geoffrey Jacquez2, PhD,
1 Environmental Health Sciences, University of Michigan School of Public Health, 109 S. Observatory, SPH-I, Ann Arbor, MI 48109.
2 BioMedware, Inc., 516 North State Street, Ann Arbor, MI 48104.
Presented at the International Society for Exposure Analysis annual meeting in Philadelphia, PA, October 2004.
Existing retrospective exposure assessment methods rely on temporally aggregated estimates to investigate relationships between exposure history and disease. Examples of such methods include time window analyses, cumulative exposure assessments, and peak exposure estimates over specified time intervals. By using predetermined time windows or cumulative exposure estimates, a critical span of time could be attenuated or overlooked. A Space Time Information System (STIS) is developed to generate continuous exposure estimates, thereby permitting visual examination of whether peak exposure at any point in time is associated with subsequent disease development.
Improving exposure assessment in environmental epidemiology: Application of a Space-Time Information System (STIS) to assess arsenic exposure in drinking water
Melissa J. Slotnick1, MPH, MESc, Jaymie Meliker1, MS, Gillian Avruskin2, MS, Andrew Kaufmann2, MS, Geoffrey Jacquez2, PhD, Jerome Nriagu1, PhD.
1 Environmental Health Sciences, University of Michigan School of Public Health, 109 S. Observatory, SPHI, Ann Arbor, MI 48109.
2 BioMedware, Inc., 516 North State Street, Ann Arbor, MI 48104.
Investigation of the relationship between environmental contaminants and disease often involves retrospective assessment of chronic low-level exposures. Current methods for assessing these exposures are prone to misclassification due to inaccurate recall or use of single exposure measurements. Inclusion of spatial data through the use of Geographic Information Systems (GIS) is enhancing exposure assessment in environmental epidemiology; however, these tools inadequately characterize temporal changes in exposures. A Space-Time Information System (STIS) is being developed to incorporate both temporal and spatial data into exposure assessments. This software features the ability to visualize attribute changes on a continuous time scale, and to capture important characteristics of exposure that are lost with traditional GIS. Application of a STIS for reconstructing arsenic exposure in a population-based bladder cancer case-control study will be presented. Cases, recruited from the Michigan State Cancer Registry, and controls, selected by random-digit dialing, are asked to complete a telephone interview and written questionnaire to assess water consumption patterns and residential history. A STIS facilitates inclusion of spatial data, such as residence location and arsenic concentration maps, and temporal information, such as residence mobility and changes in drinking water arsenic concentration over time, to improve exposure assessment. Sensitive time-windows of exposure and potential disease clusters at different points in time will be presented, thereby illustrating the potential of a STIS to reveal associations that may fail to be detected with traditional GIS. Demonstration of this valuable tool provides insight into improving exposure assessment methodologies for numerous applications in environmental epidemiology.
STIS is used to visualize estimates of lifetime exposure to arsenic in drinking water among participants in a population based bladder cancer case control study in southeastern Michigan. Cases were recruited from the Michigan State Cancer Registry; controls were frequency matched to cases by age (5 years), race, and gender, and recruited using a random digit dialing procedure from an age weighted list. Participants answered a telephone questionnaire concerning drinking water habits, and completed a written questionnaire describing residential and mobility history. Water samples were collected at current residence and analyzed for arsenic; arsenic concentration in drinking water is estimated at previous residences.
Exposure histories for 18 cases and 25 controls are presented to demonstrate applications of STIS. This size dataset allows for straightforward manipulation and visualization of complex exposure scenarios, enhancing communication of the intricacies of STIS. Datasets will be presented, with emphasis on the capability of STIS to transform datasets and permit visualization of continuous exposure histories. Exposure life lines will be exhibited to illustrate how a researcher could investigate if any years of high exposure are more prominent in cases compared with controls. These exposure life lines convey critical information regarding timing of exposure and subsequent disease development. Through enhancing exposure assessment methodology, STIS enjoys numerous applications in environmental epidemiology.
Creating a Space Time Information System to Investigate Arsenic Exposure in Drinking Water
AvRuskin, Gillian A., Jaymie R. Meliker, Melissa J. Slotnick, Andrew Kaufmann, Geoffrey M. Jacquez, and Jerome O. Nriagu.
Creating a Space Time Information System to Investigate Arsenic Exposure in Drinking Water. GIScience 2004, University of Maryland