Pesticides released into the environment may pose both ecological and human health risks. Governments set the
regulations and guidelines for the allowable levels of active components of pesticides in various exposure
sources, including drinking water. Several pesticide risk indicators have been developed using various methodologies,
but such indicators are seldom used for the selection of pesticides to be included in national regulations
and guidelines. The aimof the current studywas to use risk indicators for the selection of pesticides to be included
in regulations and guidelines. Twenty-four risk indicators were created, and a detection rate was defined to
judge which indicators were the best for selection. The combination of two indicators (local sales of a pesticide
for the purposes of either rice farming or other farming, divided by the guideline value and annual precipitation,
and amendedwith the scores fromthe physical and chemical properties of the pesticide) gave the highest detection
rates. In this case study, this procedurewas used to evaluate 134 pesticides that are currently unregulated in
the Japanese Drinking Water Quality Guidelines, from which 44 were selected as pesticides to be added to the
primary group in the guidelines. The detection probability of the 44 pesticides was more than 72%. Among the
102 pesticides currently in the primary group, 17 were selected for withdrawal from the group.