Police around the world have 'not learned' the appropriate times to use tear gas, according to an investigation across 22 countries

• Police have launched tear gas on crowds of Black Lives Matter protesters from Washington DC to California and Minneapolis in recent weeks.
• Tear gas, a chemical irritant, is used legally to control crowds, but human rights experts say it should only be deployed as a last resort to disperse violent riots.
• "In practice, police forces use tear gas in ways that it was never intended to be used," Amnesty International said Thursday, in a new report.
• The human rights group has surveyed video from more than 50 tear gassing events in 22 countries around the world since 2018.

Tear gas has become a first line of defense to curb protests across the US in recent weeks, from the streets of Minneapolis, to Washington DC, and Philadelphia.

When the chemical comes in contact with people's skin, eyes, and lungs, it dissolves into a painful, acidic liquid, triggering a burning sensation and leading to coughing, difficulty breathing, and crying.

This crowd control move — which is designed to push packs of people to disperse, seeking fresh air — has become a far too common strategy for getting rid of lawful demonstrators, and just getting people to go home, according to a new multimedia tear gas tracking site from Amnesty International.

"Law enforcement has not learned, in terms of how to deploy tear gas, and in what situations," Justin Mazzola, Deputy Director of Research at Amnesty International USA told Insider, shortly before the group's interactive site, "Tear Gas: An Investigation," was released on Thursday. "In front of the White House the other day ... it was used as a first resort, to clear people out as fast as possible, rather than giving people a warning, letting them know it's going to be used, why it's going to be used."

On Thursday, Rep. Alexandria Ocasio Cortez is expected to introduce a bill in the US House of Representatives, proposing to ban tear gas (and other chemical weapons) from police force use.

"It is one of the most basic steps we can take," she told the Los Angeles Times.

Tear gas is deployed around the world to make peaceful people go away

The issue of tear gas overuse is not confined to the US. Around the world, the same scenario has played out again and again, in over 50 different gassings across 22 countries since 2018, Amnesty's investigators found.

Tear gas has been misused on peaceful demonstrators, in confined spaces, on vulnerable populations (such as kids and older adults), and deployed in direct fire and excessive amounts.

As the coronavirus spread through Kenya in March, people were tear gassed "arbitrarily" while trying to board a ferry home, hours before curfew began.

Funeral processions have been met with tear gas in Bolivia and Guinea, before and after contentious national elections in those countries. Tear gas was also dispersed by police into hospitals, homes, and schools in Chile to quell citizens' calls for better health, water, and education in that country, and it has been showered on climate protesters in Paris, and crowds of Americans peacefully assembling for Black Lives Matter protests in cities around the US.

Police departments are using tear gas "whenever they feel it's necessary"

Experts say that tear gas should be used as a last resort weapon to disperse a violent crowd, where there is widespread rioting and vandalism, as has happened occasionally in the US after big sports wins.

"I wouldn't go so far as to say there's absolutely no role for tear gas, especially in violent settings," Dr. Rohini Haar, an emergency physician and crowd-control weapons expert with Physicians for Human Rights, previously told Insider. "But I would say that the level of widespread use — not just in the US but abroad — and how frequently it's misused, should give people pause."

Part of the problem, Mazzola said, is police access.

"If you give law enforcement agencies a tool, they're going to use it," he said. "They will use them whenever they feel it's necessary, rather than when it's actually appropriate and proportionate to the threat that they're actually facing."

This overuse can have crippling consequences.

Tear gas canisters can injure and kill

Balin Brake, a 21-year-old Indiana Tech student, lost his right eye after a tear gas canister hit his face during a protest in Fort Wayne on May 30.

Brake is not the only one who's been hurt.

Haar authored a case study of kinetic impact projectiles (KIPs), published in the BMJ in 2017, which found that KIPS, including tear gas canisters, rubber bullets, and bean bag rounds, "have caused serious injury, disability, and death."

Of the 1,981 people who sustained injuries in the 26 studies used for that analysis, Haar and her co-authors found 53 people had died from their injuries, 71 sustained severe injuries, and 300 suffered permanent disabilities.

Other, more common injuries include tearing, redness, pain, and the gas can also prompt asthma issues. During a coronavirus pandemic, there's another risk added to the pile: the irritation and coughing that tear gas prompts can help promote viral spread.

In Washington DC, many National Guard members are not sitting well with the recent tear gas deployment near the White House.

"Typically, as the DC National Guard, we are viewed as the heroes," First Lt. Malik Jenkins-Bey, who was acting commander of the 273rd Military Police Company during the gassing, told the New York Times. "It's a very tough conversation to have when a soldier turns to me and they're saying, 'Hey sir, you know my cousin was up there yelling at me, that was my neighbor, my best friend from high school.'"

At Amnesty International, Mazzola said the time is ripe for some kind of reform.

"I think the past few weeks really demonstrate that we need national guidelines in terms of how all of these equipment is used," he said.