According to this version, Jawaher Abu Rahma was standing 150-180 meters away from the kids throwing stones who were hit with tear gas.
This is nearly two football fields away.
As we saw yesterday from the Physicians for Human Rights paper on tear gas, the immediate cloud produced is some 6-9 meters in diameter and even in the center of the cloud the concentrations of the agent are 3%-10% of the amount usually needed to be breathed in for a full minute to kill the average healthy person.
I can't find any studies on dissipation of CS gas outdoors but simple watching of videos of these demonstrations shows that the gas cloud dissipates within seconds (although the canister emits gas for maybe 10 seconds so if one was right next to the canister one could be exposed at the highest outdoor levels for perhaps 15 seconds.)
While I have no doubt that someone can smell tear gas from a greater distance and even that their eyes can tear from a whiff, the idea that tear gas is toxic from 150 meters is absurd. The entire town of Bil'in would have been wiped out years ago.
(h/t Yisrael Medad and SoccerDad)