Possible Relationship Between Nitrate in Drinking Water and Childhood Type 1 Diabetes Mellitus in the Netherlands. H. J. Albering, telephone (031) 43-3881088, fax (031) 43-3670924, e-mail H.Albering@GRAT.Unimaas.NL, J. M. S. van Maanen, S. G. J. van Breda, and D. M. J. Curfs, Department of Health Risk Analysis and Toxicology, Maastricht University, Maastricht, The Netherlands; M. Reeser, Juliana Children's Hospital, The Hague; J. Fritz and R. A. Hirasing, TNO Prevention and Health, Leiden; B. Wolfenbüttel, Department of Internal Medicine, Academic Hospita1 Maastricht, Maastricht, The Netherlands; and J. C. S. Kleinjans, Department of Health Risk Analysis and Toxicology, Maastricht University, Maastricht, The Netherlands
During the past decades, the incidence of type 1 diabetes mellitus has increased. The causes of the increasing incidence as observed in several countries are unknown. Exogenous as well as endogenous factors appear to be involved in the onset of childhood IDDM (insulin-dependent diabetes mellitus). Nitrate exposure is one of the exogenous factors postulated in IDDM etiology. Two ecological studies, in the US (Colorado) and the UK (Yorkshire) suggest that nitrate levels in drinking water are positively correlated with IDDM. The present study investigates the geographical differences (based on postcode areas) in incidence of IDDM in relation to the nitrate concentration in drinking water in The Netherlands. Postcodes provide a hierarchic classification of addresses. Any address consists of a postcode area (comprising 4 figures), which can further be divided into individual postcodes (6 figures), which are unique for a small number of dwellings. In The Netherlands 3932 postcode areas are defined, which comprise addresses from a small villages to town districts. From 1993 onwards the Dutch Observation Centre of Pediatrics registered the incidence of IDDM. In the age group of 0-14 years a total of 1081 children were diagnosed with IDDM between 1993 and 1995. The registration covers the year of diagnosis, age at diagnosis (0-4 years), sex and the postcode of residence at diagnosis. The nitrate levels in drinking water within each postcode area have been obtained from the National Institute of Public Health and the Environment and 25 water supply companies. Regulations under the water supply act requires that per 10.000 inhabitants the water supply companies have to measure nitrate levels twice a year. 23248 nitrate levels in drinking water from 1991-1996 were available. To obtain the nitrate exposure within each individual postcode area, mean values based on the samples taken from 1991 to 1996 were calculated. Statistical analysis is in progress and the results of this study will be presented and the implication for human health will be discussed.
Conclusions: The representative aggregated indicator for drinking water supply is the size of population with access to safe water: size of population supplied with drinking water out of which size of population supplied with water in compliance with standards and size of population continuously supplied.
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