Purpose: The aim of the study was to develop a microbiological-chemical risk assessment model to quantify the risk associated with the use of tap water in France for preparation of infant formula (during the first six months of life).
Methods: Cryptosporidium spp. and arsenic were selected as the hazards of greatest concern in microbiology and chemistry, respectively. The risk assessment model, with uncertainty and variability separated, was built using French data (or European data, alternatively). Outputs were expressed, firstly, at the individual level, as probability of illness; and then, at the population level, by using the DALY (Disability Adjusted Life Year) indicator. Two scenarios of milk preparation were considered: the use of boiled and unboiled tap water.
Results: Consuming infant formula rehydrated with unboiled tap water during the first six months of life led to 6,000 DALY per 100,000 infants (90% uncertainty interval [1500; 12000]) for Cryptosporidium spp. causing diarrhea and 2 DALY [1.6; 2.3] for arsenic causing lung and bladder cancers. For the whole infant population, boiling water would suppress the risk from Cryptosporidium spp. In contrast, the cancer risk, although low at the population level, was rather high for infants having a high level of exposure to arsenic. For those, exposure would be decreased by changing the tap water supply point.
Significance: This model can help authorities quantify the risk associated with tap water used for preparation of infant formula. More generally, it is an example of a microbiological-chemical risk assessment and, thus, falls into the emerging risk-benefit assessment area.