Hundreds report abnormal menstruation after being teargassed during Portland protests

More than a thousand people reported lasting health effects after being exposed to teargas during protests in Portland, Oregon, last summer, according to a newly published scientific study.

Nearly 900 people reported abnormal menstrual cycles, including intense cramping and increased bleeding, that began or persisted days after their initial exposure to the teargas. Hundreds of others complained of other negative health impacts, including severe headaches, nausea, diarrhea, and mental health concerns.

The new research, based on an online survey of more than 2,200 people, challenges claims that the health consequences of being teargassed are minor and temporary, said Dr Britta Torgrimson-Ojerio, a researcher at Kaiser Permanente Northwest and the lead author of the study.

Related: Teargas used on Portland protesters risks ‘grave health hazards’, says lawsuit

It is also the first published, peer-reviewed study to confirm a link between teargas and abnormal menstruation, a connection that was widely discussed by American protesters on social media and in news reports last year.

Participants in racial justice protests against police violence last summer in Portland, Seattle, Minneapolis, Rochester and other cities told media outlets that their exposure to teargas had been followed by unexpected bleeding, unusually painful cramps, and other disruptions of their typical menstrual cycles.

Last July, Oregon Public Broadcast interviewed 26 protesters, ages 17 to 43, who said that exposure to teargas had affected their periods. Some described large blood clots, others “cramps that felt like sharp rocks”.

“We’re not paranoid. This isn’t a coincidence. Something’s going on,” one 29-year-old protester told Oregon Public Broadcasting.

Five transgender people who were taking testosterone, which typically stops menstruation, told the radio outlet that they had seen cramps and bleeding start again after exposure to teargas.

In Seattle, more than a dozen people, including some who were not present at protests but had been exposed to teargas drifting into their homes, told KUOW they believed their periods had been affected.

One of the reasons the researchers decided to conduct a survey last summer is that little is known about the health effects of teargas when it is deployed on a civilian population that is made up of a wide diversity of people, said Torgrimson-Ojerio.

Despite this lack of knowledge, she said, “teargas is being deployed regularly, night after night, in a general community,” affecting “people who are pregnant, people who are vulnerable because they have other diseases, potentially children or minors, much older adults”.

The results of the Portland study, including the new link between teargas and menstruation, are an important contribution to the scientific research on teargas, which has primarily been tested on younger men in military and police settings, said Sven-Eric Jordt, a professor of anesthesiology at Duke University.

“At this time, we don’t know how teargas causes these [menstrual] irregularities,” Jordt told the Guardian. “It is possible that pain, stress, dehydration and exertion play a role. Alternatively, teargas degradation products in the human body may have endocrine effects.”

While the current medical advice for dealing with the effects of teargas is simply to walk away, remove clothing affected by the chemicals, and take a shower, the survey responses suggest that physical and mental health effects of being teargassed may be much more lasting, Torgrimson-Ojerio said.

Some respondents reported “medical issues and mental health issues that have lasted for days, sometimes weeks, up to months after their exposure”, she said.

More than half of the people in the survey who menstruated described some kind of irregularity in their periods, or breast and chest tenderness, after being teargassed.

Some respondents to the Kaiser Permanente Northwest survey described cramps so severe that they reported needing to seek medical attention from an urgent care clinic or emergency room, she said.

The researchers also found a “dose response”: people who described more frequent and repeated exposure to tear gas also described more serious disruptions to their menstrual cycles.

The new study, published in BMC Public Health, has some limitations. The results are based on an anonymous online survey, so researchers were not able to independently confirm the identities of the respondents, Torgrimson-Ojerio said.

“Any time people are reporting big changes in their body and their health, it is concerning,” she said. Because researchers were not able to follow up with respondents about how the symptoms they experienced affected their lives, “we can’t say anything definitively about how bad this was”.