The presence of U.S. agents has diminished in Portland, Oregon, but city officials are still cleaning up tear gas residue from the streets, dirt and possibly the storm drains after the chemical was used frequently by both police and federal officers during more than two months of often-violent protests over racial injustice.
The Portland Bureau of Environmental Services cleaned and took samples from six storm drains last week around the federal courthouse and a building with a police station and jail that have been targeted in nightly demonstrations.
Environmental officials aimed to prevent pollutants from reaching the Willamette River, which runs through downtown and is popular with kayakers, canoeists and boaters, and determine the possible impact if contaminants did flow into the waterway.
"There is no American city, that I am aware of, that has endured the level of tear gas," agency spokeswoman Diane Dulken said. "We are researching and looking through environmental literature. What are these materials and their toxicity?"
Officials said they're testing for pollutants that are found in crowd control agents such as the heavy metals zinc, lead, copper and chromium.
Dulken said there is no evidence yet of tear gas residue reaching the river, "but it's also hard to say because there is so much unknown about the materials and so much unknown about the quantities."
U.S. Rep. Earl Blumenauer of Oregon and state Rep. Karin Power sent a letter last month to the U.S. Environmental Protection Agency and the Oregon Department of Environmental Quality requesting an investigation into "the public health and environmental risks of tear gas and other chemicals to people, wildlife, aquatic life and local air and water quality."
Blumenauer and Power asked the EPA for information on what kind of chemicals federal agents used and how the residue will be cleaned up.
"We don't know yet what has been deployed, but we aim to find out," Power said.
The protests over racist policing often ended with a fog of tear gas as federal agents tried to disperse the crowd. Before they arrived, local police frequently deployed it. The protests started after the death of George Floyd while in police custody in Minneapolis, dwindled to smaller groups that spread chaos and grew again when President Donald Trump sent federal agents to the liberal city in early July. Violence has persisted, but the gatherings over the last week have been much smaller and targeted local police facilities.
Demonstrators and city officials said agents' use of tear gas was excessive, but U.S. authorities said it was necessary to protect federal property and officers as protesters hurled objects like cans of beans, bottles and fireworks.
Robert Griffin, who is the dean of the College of Emergency Preparedness, Homeland Security and Cybersecurity at the University at Albany in New York, said he was "a little bit appalled" by the use of tear gas.
"If you put a cloud of gas into a crowd, it's going to affect the old, it's going to affect the young, it's going to affect the youth. It doesn't pick," Griffin said. "The problem is, if the wind shifts, it will go into areas that it was never intended to go."
While local officials have called for a study on the impact of the chemical irritants, Griffin said that should have been done much earlier.
"We should be putting money into understanding the long-term health and impacts of these technologies because they are being used on our own citizens," Griffin said.
Sven-Eric Jordt, an associate professor and researcher at Duke University's School of Medicine who has extensively studied tear gas, said the majority of data used to justify its use is outdated, having been generated in the 1950s, '60s and '70s.
"It's really very distressful that the science is really so old," Jordt said.
Documents listing the ingredients in the gas, as well as the amount used on Portland protesters, haven't been released.
"I really think that the federal government and also local health departments have really neglected their duty to reinvestigate the safety of tear gas," Jordt said.
At the end of July, federal authorities were pulled back from downtown Portland and the cleanup began.
The city Bureau of Environmental Services received reports of power-washing that possibly flushed contaminants from the streets into storm drains. While some lead to a sewer system, the drains surrounding the federal courthouse lead directly to the Willamette River. Officials told city workers to put buffers around storm drains while cleaning.
The river has a history of pollution, which was stained with sewage as often as 50 times a year and for decades carried industrial pollution from several Oregon cities. Today, people swim in the river that's now considered safe.
Dulken said Portland has worked to be proactive about stopping pollutants from reaching the river, including any tear gas residue.
Authorities took samples from the entry and exit points of the storm drains and expect results later this month, which could lead to further cleanup.
"What is the effect? We don't know," Dulken said.