Risk assessment of nitrate in drinking water
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This is the main page of the WP3.4 assessment of the health impacts of nitrate in drinking water. This and the articles linked to it describe the first pass assessment.
- There is considerable general material available on this wiki on the development of the WP3.4 assessment
- The article on the WP3.4 First pass assessment provides an overview of all the assessments grouped under WP3.4
- The models described on this page are Analytica files. While the software is proprietary (i.e. not free), a free viewer (Analytica player) is available in which models can be investigated, and a free trial version is available at the Lumina Decision Systems website.
This is the main page of nitrate risk assessment conducted in INTARESE WP3.4. The analytica file can be uploaded here: File:Nitrate.ANA. Detailed information about nitrates in drinking water is found in INTARESE wiki.
To investigate the effects of nitrate contaminated drinking water.
European countries in selected regions:
- First pass assessment:
- England and Wales
- Second pass assessment:
- England and Wales
- Infants < 6 months of age
- Exposure to nitrate via baby food formula mixed with drinking water and via drinking water (onlt tap water in the first pass asessment)
- Effects: infant methemoglobinemia (iMetHb). More detailed information about methemoglobinemia and other nitrate related health effects is found in INTAESE wiki.
This assessment focused only on the current situation, therefore scenarios are not included in the assessment. In the future the assessment may contain the following scenarios:
- Drinking water source: Tap water or well water
- Increased use of bottled water
For the first pass it was deemed appropriate to carry out a diagnostic assessment i.e. to estimate the scale of the health impacts under present conditions, which in this case make use of 2003 as the baseline year. We also looked at only areas in England and Wales. It was recognised that the causal diagram should be constructed in such a way that the introduction of policy scenarios is possible, since this is intended for the second pass of the assessment. The introduction of such potential policy scenarios would allow the diagnostic assessment to be transformed into a prognostic assessment i.e. a causal diagram which allows the estimation the likely consequences of different policy options, primarly as a basis for choosing between them. 
- Researchers at KTL
- Researcher at Imperial College London
- Researchers at London School of Hygiene & Tropical Medicine
- Researchers at Municipal Institute of Medical Research Foundation
Detailed documentation of the design, elaboration and construction of the causal diagram to be used in this assessment is given in article found in |INTARESE wiki. The final draft is presented in figure 1. The working Analytica version of the nitrate model File:Nitrate.ANA.
- Drinking water source (population using public/private water supplies)
- Health risk estimates for iMetHb
- Excess cases of iMetHb
- Total ingestion of nitrates from drinking water by infacts < 6 months
- Nitrate concentration in drinking water
- Exposure of infants < 6 months to water from private supply
- Infection status of infants < 6 months
- Exposure response function for nitrate and iMetHb: Detailed discussion of this can be found in INTARESE wiki
- Water companies in England and Wales
- Finland areas
- Water source
Calculating from Excess cases of iMetHb the following numbers:
- Std. Dev.
Excess cased of iMetHb
Table 1. The statistics of excess cases of iMetHb in areas of England & Wales.
The median of excess cases of iMetHb is low (under 0.01 cases for each area), which is due to low consumption of drinking water, a very low background prevalence of iMetHb and low nitrate levels in drinking water.
The results of integrated environmental health impact assessment for nitrate in drinking water causing iMetHb indicate that there is a risk of iMetHb with high levels of nitrate, though the nitrate levels in drinking water in UK are low. The number of excess cases of iMetHb was under one in each of the studied areas. The major sources of uncertainty in the assessment and results were total daily consumption of water by infants, nitrate concentrations in drinking water and background prevalence of iMetHb. The uncertainty of the ERF slope was unknown. Confounding factor of pathogens was excluded from the assessment and should be taken into account in any future assessment.
- Briggs DJ. Integrated assessment for policies on environmental health. Draft. Unpublished document. 2008.