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There isn’t enough research to know if tear gas causes early periods

There isn’t enough research to know if tear gas causes early periods


It’s dangerous regardless

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A protester return throws tear gas towards the police who...
Protestor throws a tear gas canister back towards police officers.
Photo by Stanton Sharpe/SOPA Images/LightRocket via Getty Images

Sarah Trad and Christina Lower were both caught by the edge of a cloud of tear gas when they attended a protest against police brutality early this month. They weren’t in the direct line of fire, but they both felt the effects of the gas, like tingling skin and watering eyes.

Trad started her period early, a few days later, and experienced more cramping than usual. After seeing social media posts about a possible link between early periods and tear gas, she texted Lower to ask if her period had come early, too.

It had — the night that Lower had been exposed to the gas. In fact, her period was about five days early, which was unusual. “I said, wow, that just seems like too much of a coincidence,” Lower says.

On social media, other people said they’ve had similar changes to their menstrual cycle after being exposed to tear gas. The abortion rights advocacy group NARAL Pro-Choice Ohio warned on Twitter that these chemicals are “known to cause miscarriages.” But scientists know very little about the effects of tear gas on the body, including how it might affect the female reproductive system. That makes it hard to understand experiences like Trad’s and Lower’s. 

There’s very little research on tear gas, in general, says Rohini Haar, research fellow in the Human Rights Center at UC Berkeley and medical expert with Physicians for Human Rights. “The reality is these substances haven’t been well-studied,” says Daniel Grossman, professor of obstetrics and gynecology at the University of California San Francisco. “The bottom line is they’re weapons of war, and they’re designed to harm people’s bodies. As a medical provider, I can’t condone their use on anyone.”

A handful of different groups have reported a link between tear gas — which is made from the chemical compound chlorobenzylidene malononitrile — and miscarriages. The Chilean government banned the use of tear gas after a University of Chile group reported it could cause miscarriages. The nonprofit group Physicians for Human Rights documented pregnancy loss in women exposed to chemical agents in Bahrain in 2012. 

“There are many, many miscarriages,” a nurse in the region told the Physicians for Human Rights investigators. “We believe the miscarriage rate has increased, although there is no quantitative evidence.”

“It really has the effect of people essentially losing their right to protest, if they’re pregnant or think they’re pregnant”

The incidents are only anecdotal, but they’re alarming, Grossman says. “It really has the effect of people essentially losing their right to protest, if they’re pregnant or think they’re pregnant.”

There’s even less information on menstrual changes. Laurel Zwissler, a professor of religion at Central Michigan University, was exposed to tear gas with protesters in Quebec City in 2001. One protester started bleeding in the middle of her cycle. Zwissler also had an especially painful period, she reported in her book on feminist, religious activism. Dozens of women at those protests emailed the group Science for Peace and said that they started their periods early. It was unsurprising to activists, who told Zwissler “tear gas does that.”

The unknown effects of tear gas, particularly on women, are a perennial concern in activist communities, Zwissler said in an email to The Verge. 

Tear gas has been used against people for decades, under the assumption it doesn’t cause long-term harm. But we don’t know that for sure — and the tear gas being used now isn’t necessarily what was used 100 years ago, Haar says. Even if something called tear gas was low-risk in the past, it may have more dangerous components today.

It’s unethical to test tear gas on people to answer these questions. The best researchers can do is use animals to mimic the effects gas might have on a person, Haar says. Researchers can collect first-hand accounts from people who were exposed to tear gas at protests, but it’d be hard to tease out if any long-term effects were from the gas itself or from the stress of the experience. “There are so many things that happen at a protest,” she says. 

But just because it’s difficult to study tear gas doesn’t mean we shouldn’t try to find out what it does

But just because it’s difficult to study tear gas doesn’t mean we shouldn’t try to find out what it does. Physicians for Human Rights, for example, called for the research community to study the effects of tear gas on miscarriage in their 2012 report. “It would be really important to investigate more people’s experiences,” Grossman says. “This is an area where we don’t have a lot of high quality evidence.” 

While the data may be useful, there doesn’t need to be conclusive evidence of a link between tear gas and miscarriage to say that it shouldn’t be used. “We don’t need a randomized controlled sample to say you shouldn’t tear gas,” Haar says. “We know that it can’t possibly be good for you.”

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