Scientists identified a green, poisonous gas used by Federal agents on Portland protesters

To analyze the unknown chemicals, CWRC enlisted the help of a local laboratory, Specialty Analytical. The results, first published in a press release on October 10, confirmed suspicions that federal law enforcement was using a new compound on Portland protesters. Canisters collected from protest areas contained trace amounts of hexachloroethane (commonly HC), a white powder that, when heated in the presence of metal salts, reacts to form a dense cloud of green or white smoke that smells like camphor and wreaks havoc on biological systems.

HC is a highly regulated toxin, labeled as a “likely carcinogen” and skin irritant by the Environmental Protection Agency. Eye masks and gloves are recommended for people who handle the chemical. Defense Technologies, an imprint of Pennsylvania-based security equipment manufacturer Safariland, markets the HC canisters as “military-style” smokers, even though the U.S. military actually stopped using HC in grenades in the 1990s due to its extreme toxicity.

Activists are more concerned about the chemicals that leave the canister than those packed inside it. Firing an HC grenade triggers a two-stage reaction in which the chlorine in HC rapidly combines with metallic zinc, resulting in zinc chloride, a toxic metal fume that appears as a greenish-white smoke. “It’s a chemical reaction in a can,” says Simonis. “The zinc chloride is an intentional product of the grenade’s design.” The Material Safety Data Sheet supplied by Safariland, however, doesn’t mention zinc chloride at all.

Gaseous zinc chloride, also known as hexite, is more than an alternative type of tear gas. Because it contains the super-hot gaseous forms of both chloride ions and zinc, a heavy metal, hexite plumes are highly mobile and extremely dangerous to most forms of life. The chloride ions increase the uptake of zinc particles by exposed cells on the skin or mucous membranes. Zinc can accumulate in tissues and organs, then mobilize later and cause a new set of symptoms. The most striking effects of zinc chloride toxicity in the street — vomiting, burning skin, coughing — are only the first onslaught of a chronic, unpredictable respiratory condition that can cause severe liver damage, fatigue, weight loss, and anorexia, in addition to difficulty breathing.

Zinc toxicity sharply contrasts with the effects of tear gas, which tend to be excruciating but short-lived, with dangerous exceptions. “[Conventional tear gas] causes pain through a specific mechanism,” says B. Zane Horowitz, PhD, an emergency toxicologist in the Portland area and author of a recent op-ed decrying the city’s use of tear gas on protesters in the journal Toxicology Communications. Tear gas shorts the nervous system’s pain response, essentially creating the experience of pain without doing lasting damage — most of the time. Still, says Horowitz, “There’s no reason to have pain inflicted on you if you haven’t done anything wrong.”