Tear gas is no joke. Despite the fact that it is banned for wartime use by the Geneva Convention, police in the US use the stuff to strong-arm crowds and temper (what they allege to be) riots. But the practice has attracted revised scrutiny in the past year — nationwide protests against police brutality and racism begat more brutality, which hospitalized civilians with injuries from "less lethal" weapons, including tear gas. 

In a new study, researchers from Kaiser Permanente Northwest Center for Health Research report results from a survey of 2257 adults who attended protests Portland, Oregon. "Almost all respondents," they wrote, had physical or psychological injuries after tear-gas exposure. Nearly 94 percent felt their injuries immediately, and 86 percent had them for days. The study provides scientific support to growing pleas for banning tear gas as a method of crowd-control.

Tear gas is an irritant made of tiny solid chemical aerosols. One common ingredient, chloroacetophenone, is the eye-mouth-throat-lung-skin-burning stuff in Mace. Officials have historically greenlit tear gas as a short-term deterrent — as the chemical equivalent of batting someone's hand away when they're annoying you. But the underlying safety data is decades old and based on exposure in young healthy men. 

Doctors have known for years that chemical irritants cause serious injuries and even death. This new study presents another compelling case. The survey was anonymous and optional. It took place between July 30 and August 20 and was distributed around Facebook, Twitter, Reddit, and Instagram. The responders reported immediate symptoms like blurred vision and tearing, burning noses, chest tightness and coughing. Hundreds (about 20 percent) even reported rashes and burns.

In contrast with the myth that tear gas is just a short-term irritant, over 80 percent cited delayed health issues. Over half of people who menstruate reported menstrual changes and breast tenderness. The researchers argue that tear gas caused this effect: More days of tear gas exposure led to increased chances of symptoms. The researchers compared survey responses among people who experienced one day of tear gas versus up to five or more days. Mentions of menstrual cramping doubled from 24.3 to 50.9 percent, of increased bleeding nearly tripled, from 14 to 38.3 percent, and of clotting jumped from 3.1 to 20.2 percent.

These new results confirm what many scientists and advocacy organizations have long been saying: Tear gas is brutal on the body. It's banned in warfare, but not still around in policing. Whether the nation's patchwork of powerful municipal police systems will reckon with this fact, however, is another story.