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Parish classification or dwelling coordinate for exposure assessment in environmental epidemiology: A comparative study using Geographical information System
Linköping University, Department of Clinical and Experimental Medicine, Occupational and Environmental Medicine . Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Medicine, Occupational and Environmental Medicine Centre.
University of Gothenburg.
Linköping University, Department of Medicine and Health Sciences, Division of Preventive and Social Medicine and Public Health Science. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Clinical and Experimental Medicine, Occupational and Environmental Medicine . Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Medicine, Occupational and Environmental Medicine Centre.
2008 (English)In: Science of the Total Environment, ISSN 0048-9697, Vol. 405, no 1-3, 324-329 p.Article in journal (Refereed) Published
Abstract [en]

Background: Two previous epidemiological studies on the incidence of total malignancies in Sweden after the Chernobyl accident have shown consistently increased risks. The first study used an analogue map on (CS)-C-137 from 1986 to classify individuals in terms of the parish they lived in. In the second study, dwelling coordinates were matched to a digital map from the year 2000 to assess the individual exposure. To establish the accuracy of the exposure assessment using the larger unit of parish, instead of coordinates, we decided to compare the methods.

Methods: On the analogue map eleven isolines on the deposition of Cs-137 (kBq/m(2)) were used to classify all individuals in each of the 450 parishes. Using the digital map, by contrast, each dwelling with its inhabitants could be matched to Cs-137 deposition at a coordinate level. A population-weighted average of Cs-137 deposition was calculated for each parish. In total, 1,126,960 individuals and 450 parishes were included and analysed into six different exposure categories.

Results: Using the new parish exposure index, 111 out of the 450 parishes were reclassified as a result of the increased resolution of the digital map (86 parishes) or unequal distribution of the population compared with the deposition (25 parishes). Seventy-five per cent of the parishes remained in the same exposure category as on the analogue map.

Conclusion: Using dwelling coordinates for exposure assessment may not always be superior to parish classification. Nor is it always a cost-effective way of estimating the exposure, especially if the exposure in a parish is relatively homogenous or if parishes can be merged into broader categories with little intra-parish difference.

Place, publisher, year, edition, pages
2008. Vol. 405, no 1-3, 324-329 p.
Keyword [en]
Analysis, Caesium-137, Chernobyl, Disease, GIS, Health, Malignancies, Method, Spatial
National Category
Medical and Health Sciences
URN: urn:nbn:se:liu:diva-16141DOI: 10.1016/j.scitotenv.2008.07.019OAI: diva2:133229
Available from: 2009-01-08 Created: 2009-01-07 Last updated: 2009-08-21
In thesis
1. Malignancies in Sweden after the Chernobyl accident in 1986
Open this publication in new window or tab >>Malignancies in Sweden after the Chernobyl accident in 1986
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

On 26 April 1986 an accident occurred in the Chernobyl nuclear power plant resulting in the release of large amount of radionuclides. Almost five percent of the total released caesium-137 was deposited in Sweden. The incidence of malignancies in the most affected counties in Sweden was investigated in three epidemiological studies.

In the first study the incidence of malignancies in children and adolescents was studied for the period 1978-1992. The parishes and their inhabitants were classified according to the ground deposition of caesium-137 on an analogue map provided be the Swedish Radiological Protection Authority. A continuous increase of brain tumour incidence observed during the time of the study had no clear relationship to the Chernobyl fallout. A somewhat decreased relative risk of ALL was observed in areas with increased deposition. Other malignancies showed no changes in incidence over time or with regard to the exposure of caesium-137. In study II and III we enlarged the study base by including adults. We improved the methodology by defining a cohort of subjects who lived in the same parish from 31 December 1985 to 31 December 1987. The inhabitants from seven counties were included. Parishes were classified the same way as in study I. Due to the large number of individuals six exposure categories could be created; <3, 3–29, 30–39, 40–59, 60–79, and 80–120 kBq caesium-137/m2. The inhabitants of the 117 non-affected parishes (<3 kBq/m2) served as reference. During the 1988-1996 followup, 22,409 malignancies were recorded. The MH-IRR in the fully adjusted model was 1.00 (reference), 1.05, 1.03, 1.08, 1.10 and 1.21, respectively. ERR was 0.11 per 100 kBq/m2 (95% CL 0.03;0.20). A more advanced method was used in Study III by ignoring the exposure classification for parishes, and instead matching the dwelling coordinate to a digital map of deposition of casesium-137. In spite of a more valid exposure classification the risk estimates were similar in study II and III. Also, the ERR during the longer follow-up of 1988-1999 was almost identical, 0.10 per 100 kBq/m2 (95% CL 0.00;0.23). The strongest dose-response relationship was seen in the first four years (1988-1991). No obvious excess for leukaemia or thyroid cancer was recognised in either study II or III. The estimated number of exposure related cases was calculated to 849 in study II and 1,278 in study III. Our interpretation is that we have shown an increased incidence of total malignancies with dose-response relationship for caesium-137, only a few years after the Chernobyl accident. In study IV we compared the two different ways of classifying the exposure in study II and III. Out of the 450 parishes 111 got a different classification. The similar risk estimates in study II and III could probably be explained by relatively homogenous exposure in the parishes making the intra-parish difference less influential, especially when included in categories. In study V we examined the urinary excretion of 8-OHdG in Belarussian children from areas with high and low fallout of caesium-137, respectively. We found significantly lower urinary 8-OHdG levels in children from rural contaminated areas compared to urban uncontaminated areas, suggesting an urban, rather than a radiation related, risk factor.

Using the Hill criteria for causality there is support for a causal inference between the fallout of caesium-137 from the Chernobyl accident and the increased incidence in total malignancies in Northern Sweden.

Place, publisher, year, edition, pages
Institutionen för molekylär och klinisk medicin, 2007. 57 p.
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1001
Epidemiology, Environmental, Chernobyl, ionising radiation, geographical information systems GIS, 8-OHdG, Malignancies, Low dose, Dose-response, Latency, Causalty
National Category
Public Health, Global Health, Social Medicine and Epidemiology
urn:nbn:se:liu:diva-8886 (URN)978-91-85715-17-6 (ISBN)
Public defence
2007-06-04, Aulan, Hälsans Hus, Campus US, Linköpings Universitet, Linköping, 09:00 (English)
Available from: 2007-05-15 Created: 2007-05-15 Last updated: 2009-08-22

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