These grenades contain worrisome chemicals. “The potassium perchlorate is a significant toxicant and some of it may expose bystanders, but most of it is likely burned,” he says. “The lead and chromium are highly toxic—listed as reproductive toxicants and carcinogens. Again, the amounts are small, but are of concern.”

But compared with the CS tear gas pocket grenade, which deploys the kind of tear gas protesters are likely more familiar with, the green gas grenades have a smaller number of toxic constituents. “If exposures are equal, I would consider the CS tear gas pocket grenade to be more toxic than the smoke pocket grenade,” he said.

“The green dyed smoke suggests high toxicity to protesters,” he adds, “but the effect is more psychological.”