Using a national panel web survey data with 1,224 respondents, the to b it demand model of outdoor leisure activity reduction was jointly estimated with risk perceptions about particulate matters (PM10) using an instrument variable approach. Respondents’ risk perceptions of PM10 had significant influences on the participation and demand decisions of averting behavior, while they had no significant impact on demand for daily outdoor leisure activities. Whereas the objective measure of PM10 concentration matched with respondents’ residential region had indirect impacts on averting behavior through changes in respondents’ subjective risk perceptions, Based on estimates of to bit demand model of averting behavior, respondents were willing to pay at least a monthly average of 16,000 won for a one unit reduction(based on a 0-10 linear likert)in their risk perceptions.