Use of Exposure Simulation Models and GIS-integrated health registers

EUROHEIS/SAHSU Conference March 2003Östersund, Sweden 30 – 31 March 2003

Dr. Arne Poulstrup & Dr. Henrik L. Hansen

Regional Public Health OfficeSouthern Jutland and Funen, Denmark

Vedelsgade 17 A, DK – 7100 VejleE-mail: arne@vej.eli.dk

Medical Office of Health, Province of Vejle, Denmark

Case Study:

Cancer development in an urban population due to airborne dioxin,

assessed by use of an exposure simulation model

and a GIS-integrated health register

Medical Office of Health, Province of Vejle, Denmark

Prevailing problems concerning environmental exposures and health outcomes:

Levels of exposure of individuals are often unknownAreas of exposure are difficult to demarcateTime of exposure is difficult to determineHence: the number of individuals in time and space exposed for certain levels of environmental

hazards are rarely possible to identify precisely

Medical Office of Health, Province of Vejle, Denmark

A solution to environmental exposure level assessment:

Simulation models for exposure can be used, like atmospheric dispersion models for airborne pollution:A Danish Gaussian plume model (OML) simulates the dispersion of plumes, incorporating features like Heights of one or more stacks (more sources) Smoke emissions, velocity and temperature High rise nearby buildings, surrounding terrains Atmospheric conditions, like prevailing wind

directions, wind temperatures, fall of rain, snow etc.

Medical Office of Health, Province of Vejle, Denmark

Case Study: Simulated immissions of hourly conc. of dioxin, using OML, has been geo-coded and layered into GIS.Colours represent conc. of dioxin

Medical Office of Health, Province of Vejle, Denmark

A solution to the demarcation of the exposed population:

The population at risk is identified by applying all addresses (inclusive historical) into GIS, using geo-coded addresses

And by linkage of all individuals to these addresses using the unique CPR number (10 digit number in Central Population Register [Civil Registration System])

Medical Office of Health, Province of Vejle, Denmark

All addresses since 1986 have been applied as a layer in GIS.Each address contains info on migration of every indivi-dual who lives or has lived there, as well as duration of stay

Medical Office of Health, Province of Vejle, Denmark

The boundaries of the dioxin exposure (simulated immission of dioxin > 0 pg/h/m3)is then used to demarcate the exposed area.Polygon 1.

Medical Office of Health, Province of Vejle, Denmark

Polygon 2: area withdioxin conc. ≥ 3 pg/h/m3

Medical Office of Health, Province of Vejle, Denmark

Polygon 3:area withdioxin conc.≥ 4.5 pg/h/m3

Medical Office of Health, Province of Vejle, Denmark

Polygon 4:area with dioxin conc.between 0 -3 pg/h/m3

Medical Office of Health, Province of Vejle, Denmark

Polygon 5:Area with dioxin conc. between 3-4.5 pg/h/m3

Medical Office of Health, Province of Vejle, Denmark

Solution to exposure time assessment:

Number of records are reduced to number of individualsOnly individuals who have stayed more than two years are selectedOnly individuals relevant for selected health outcome, e.g. cancer are selected

Medical Office of Health, Province of Vejle, Denmark

The selected exposed individuals in time and space are then linked to the National Cancer Registry using the CPRs.The map shows the diagnosed cancers (in dark blue) among all exposed individuals (in yellow) in polygon 1

Medical Office of Health, Province of Vejle, Denmark

Same procedure is used to select and demarcate the control area:

Selection of a suitable area (non exposure)

Selection of sufficient number of controls

Selection of individuals who have stayed sufficient time in the area

Medical Office of Health, Province of Vejle, Denmark

Final analyses of the case area will include the different bands of exposure (from 0 – 6 g-12 of dioxin/hour),

and in the analyses of health outcome (i.e. “all cancer”) in the selected open cohorts, the following confounders will be controlled for gender ratio, age stratas and at least one socio-economic variable

Medical Office of Health, Province of Vejle, Denmark

So far analyses have been made, comparing cancer rates from the exposed area from the period 1986 – 1998 with national cancer rates, and:

SIR (Standardized Incidence Ratio) and

IRR (Incidence Rate Ratio)

showed no excess of cancer in the area of exposure

Medical Office of Health, Province of Vejle, Denmark

Financially the study has been supported by grants from:

European Commission,DG for Health and Consumer Protection

Ministry of Health, Denmark