Quantitative risk assessment of noroviruses in drinking water based on qualitative data in Japan

Yoshifumi Masago, Hiroyuki Katayama, Toru Watanabe, Eiji Haramoto, Atsushi Hashimoto, Tatsuo Omura, Tsuyoshi Hirata, Shinichiro Ohgaki

Research output: Contribution to journalArticlepeer-review

36 Citations (Scopus)


Noroviruses are one of the major causes of viral gastroenteritis in Japan. A quantitative risk assessment was conducted to evaluate the health risk caused by this virus in drinking water. A Monte Carlo analysis was used to calculate both the probability of infection and the disease burden using disability-adjusted life years (DALYs). The concentration of noroviruses in tap water was estimated based on qualitative data and a most probable number (MPN) method with an assumed Poisson lognormal distribution. This numerical method was evaluated using two sets of available count data of Cryptosporidium: that collected from a river and that found in tap water in Japan. The dose-response relationships for noroviruses were estimated using assumed ID50 (10 or 100). The annual risk was higher than the US-EPA acceptable level (10 -4 [infection/person·year]) but around the WHO level (10 -6 [DALYs/person·year]). As suggested by others, since microbial concentrations are generally lognormally distributed, the arithmetic mean was directly related to the annual risk, suggesting that the arithmetic mean is more useful in representing the degree of microbial contamination than the geometric mean.

Original languageEnglish
Pages (from-to)7428-7433
Number of pages6
JournalEnvironmental Science and Technology
Issue number23
Publication statusPublished - 2006 Dec 1
Externally publishedYes

ASJC Scopus subject areas

  • Chemistry(all)
  • Environmental Chemistry


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