Puffed rice, a common snack in south asia, is often manufactured with aid of fertilizer-grade urea, which i, think can physically do harm. This practice is highly controversial and often banned, but dishonest manufacturers do use it as leavening agent.

What can be the possible physiological harm in this case? If Urea in broken down to NH3 and CO2 , then there might be less harm, as the case for ammonium bicarbonate, so unreacted Urea can do the harm. What about role of Impurity in the fertilizer?