L=LOW RISK (western country or major city in developing world)
I=INTERMEDIATE RISK (developing country, travel outside city)
S=SUBSTANTIAL RISK (few western amenities, marginal medical system, political unrest sometimes present, possible infectious disease)
H=HIGH RISK (few western amenities, marginal medical system, travel to remote areas, environmental extremes/altitude, heat, etc, infectious disease)
Pregnant women are not permitted to participate on projects rated as Intermediate, Substantial or High Risk.