25 * 0.5ug = 12ug is the upper bound for lead in Soylent reported by this article
12ug / 15ug = 1 serving of Soylent is 80% of the actionable dose for lead in a liter of drinking water
So 1.2 of Soylent servings could reach the EPA's actionable dose for lead in water. People will eat multiple servings of Soylent a day.
To get a ratio, we need to multiply by the number of liters of drinking water people drink per day (3 is recommended for men in temperate climates).
15 ug/liter * 3 liter/day = 45 ug/day would seem to be the EPA's idea of an acceptable daily dose from water.
3 servings of Soylent per day would come close, but not quite reach that level.
Of course, the EPA's action level might be unhealthfully high.
We'd have to know if the EPA based their figures on the ideal intake or the actual consumption figures.
http://www.ars.usda.gov/SP2UserFiles/Place/12355000/pdf/DBri...
I'd love to know how both limits were decided.