Jms. Van Maanen et al., Does the risk of childhood diabetes mellitus require revision of the guideline values for nitrate in drinking water?, ENVIR H PER, 108(5), 2000, pp. 457-461
In recent years, several studies have addressed a possible relationship bet
ween nitrate exposure and childhood type 1 insulin-dependent diabetes melli
tus. The present ecologic study describes a possible relation between the i
ncidence of type 1 diabetes and nitrate levels in drinking water in The Net
herlands, and evaluates whether the World Health Organization and the Europ
ean Commission standard for nitrate in drinking water (50 mg/L is adequate
to prevent risk of this disease. During 1993-1995 in The Netherlands, 1,104
cases of type 1 diabetes were diagnosed in children 0-14 years of age. We
were able to use 1,064 of these cases in a total of 2,829,020 children in t
his analysis. We classified mean nitrate levels in drinking water in 3,932
postal code areas in The Netherlands in 1991-1995 into two exposure categor
ies. One category was based on equal numbers of children exposed to differe
nt nitrate levels (0.25-2.08, 2.10-6.42, and 6.44-41.19 mg/L nitrate); the
other was based on cut-off values of 10 and 25 mg/L nitrate. We determined
standardized incidence ratios (SIRs) for type 1 diabetes in subgroups of th
e 2,829,020 children with respect to both nitrate exposure categories, sex,
and age and as compared in univariate analysis using the chi-square test f
or trend. We compared the incidence rate ratios (IRRs) by multivariate anal
ysis in a Poisson regression model. We found an effect of increasing age of
the children on incidence of type 1 diabetes, but we did not find an effec
t of sex or of nitrate concentration in drinking water using the two exposu
re categories. For nitrate levels > 25 mg/L, an increased SIR and an increa
sed IRR of 1.46 were observed; however, this increase was not statistically
significant, probably because of the small number of cases (15 of 1,064).
We concluded that there is no convincing evidence that nitrate in drinking
water at current exposure levels is a risk factor for childhood type 1 diab
etes mellitus in The Netherlands, although a threshold value > 25 mg/L for
the occurrence of this disease can not be excluded. Key words: drinking wat
er, guideline values, nitrate, type 1 diabetes.