"By the time she was standing in front of the federal courthouse on #LownsdaleSquare on the night of July 25, Olivia Katbi Smith had already been exposed to tear gas several times. On those previous occasions during the #BlackLivesMatter #protests in Portland, Oregon, this summer, being gassed had been very unpleasant: leaving her coughing and making her eyes and nose run and sting.

"But this time, standing about 30 feet from the fence that was surrounding the downtown courthouse, Smith felt suddenly and violently worse than she ever had before. 'I didn’t know if I was going to puke or pass out,' she recalled recently. 'I was stumbling, trying to get away.' Smith, who is 28, was wearing goggles plus an N95 mask and thought that whatever was making her ill might have been trapped inside her mask. 'So I made a really bad instinctual decision to take it off,' she said. 'And instead of bringing relief, it instantly felt so much worse, like I was trapped in the air. It was overwhelming. I could not breathe.'

"Smith, like thousands of others in Portland, took to the streets in June to protest the suffocation and killing of #GeorgeFloyd by a police officer. By the beginning of July, the crowds had begun to thin somewhat. But after #Trump decided to send federal law enforcement to the city that month, the number of protesters surged and violence escalated. And according to interviews with more than a dozen people who attended the protests and research by the Portland-based #ChemicalWeapons Research Consortium, there was a marked shift in the use of chemical munitions on the crowds in the second half of July, as the federal agents released greater amounts and different types of smoke and gas onto crowds that seemed to set off severe and sometimes lasting health effects.

"The Portland Police Bureau began using tear gas on Black Lives Matters protesters almost as soon as they first assembled in late May. Mayor Ted Wheeler acknowledged that the city has used '#CSTearGas.' The commonly used formulation contains 2-chlorobenzalmalononitrile, a compound that was designed to induce immediate pain but can also have long-term effects, including chronic bronchitis. In early September, Wheeler ordered the police to stop using it. #TearGas is banned in war but can be used to disperse crowds of civilians.

After federal agents from the #DepartmentOfHomelandSecurity descended on Portland in July in a mission dubbed #OperationDiligentValor,' the use of chemical irritants to control, drive away, and confuse protesters and obscure the actions of law enforcement grew and intensified. Among the products that federal agents appear to have used during the #military-style #crackdown is a #hexachloroethane '#SmokeGrenade' manufactured by a company called #DefenseTechnology and sold as '#MaximumHCSmoke.' Volunteers for the Chemical Weapons Research Consortium collected 20 canisters from the protest area that are the size and shape of the smoke grenades, at least five of which still had Defense Technology labels on them. The group also analyzed the chemical residue on one of the recovered spent canisters and found it contained chemicals known to be released by the smoke grenades."