project

Risk of opportunistic pathogens in drinking water

The water utilities have indicated that research into opportunistic pathogens in drinking water has a high priority. This is because these pathogens could represent a potential health risk. This project’s priority is to determine the risk represented by opportunistic pathogens in drinking water on two fronts. First, in relation to faecal pathogens and, second, in relation to sources other than drinking water and the gravity of the associated risk. The results should place the water utilities in a position to a make well-informed decision about the need for supplementary research into opportunistic pathogens in drinking water.

Opportunistic pathogen risks

Earlier research under the Joint Research Programme of KWR and the water utilities [ML1] showed that, besides Legionella pneumophila, the opportunistic pathogens Pseudomonas aeruginosa, Aspergillus fumigatus and Stenotrophomonas maltophilia can occur in drinking water in the Netherlands. Subsequent research then showed that the drinking water strains of P. aeruginosa and A. fumigatus are genetically similar to patient strains, indicating that the presence of these microorganisms in drinking water could represent a potential health risk. It is however unclear how this risk compares to the acceptable risk level for the presence of faecal pathogens in drinking water. This project is therefore determining what the critical concentration of opportunistic pathogens in drinking water may be, based on an infection risk of 10-4 per year, or a DALY of 10-6 per year. These concentrations will then be compared to the critical concentrations that are accepted for faecal pathogens.

Quantitative microbial risk assessment

Through reverse quantitative microbial risk assessment (QMRA), based on an infection risk of 10-4 per year and a DALY of 10-6 per year, a calculation will be made of what the critical concentrations of Legionella pneumophila, Pseudomonas aeruginosa, Mycobacterium kansasii and Aspergillus fumigatus may be in drinking water. To enable these calculations, the international literature will be examined and the parameter values it contains will be taken into account.

Opportunistic versus faecal pathogens

Currently the water utilities are fully engaged in controlling the risk of faecal pathogens in drinking water. Up until this point, however, little has been done regarding the risk of opportunistic pathogens. The project results will clarify whether the health risks justify this prioritisation, or whether the water utilities should also pay more attention to opportunistic pathogens. The project will moreover identify knowledge gaps that possibly hamper a reliable QMRA.