Pictures and video of migrant men, women and children rushing through white clouds of tear gas fired by border agents during an incident at the southern US border have brought forth anger, debate and concern.
While the morality and necessity of the riot control agent's use is certainly a topic of debate, others have also worried about the effects the substance could have on the young migrant children who were seen in the fray.
According to experts, tear gas isn't exactly what you think it is -- and it does, in fact, have the potential to have a dangerous and long-lasting effect on children.
Tear gas is more than an irritant
What exactly is tear gas? While there are a few different compounds that can be used for the purpose, the overwhelmingly common compound is called chlorobenzylidenemalononitrile, or "CS."
Tear gas is often assumed to be an irritant, like the fumes of an onion in the eyes or pepper in the nose. Recent medical research has proven otherwise, says Sven Eric Jordt, an assistant professor of anesthesiology at Duke University who specializes in sensory mechanisms
"We discovered that the chemical causes pain by activating pain receptors," Jordt says. I would consider them to be nerve agents that selectively and very potently engage pain nerves."
Children are especially vulnerable to its effects
The Centers for Disease Control says tear gas can cause blurred vision, burning and swelling in the nose, coughing, choking, shortness of breath and skin burns, in addition to other side effects.
According to the CDC, most of these effects go away after 15 to 30 minutes -- if the person is decontaminated.
That's a key step, because Jordt points out that tear gas isn't a gas at all, but rather a solid; a powder that has to be heated and mixed with a solvent.
"That's why they can deposit on the skin, hair, eyes and clothing," he says. "If [people] are not decontaminated, this can cause injuries."
Children are at an even higher risk for injuries -- both at the time of exposure and later on.
"Children are especially at risk because tear gas is heavier than air," says Jordt. "It is present in higher concentrations closer to the ground, and children, being shorter, are exposed to higher concentrations. Also, since their lungs are smaller, when they inhale tear gas the potential for injury is higher."
It affects their long term health
These reasons were echoed in a statement by the American Academy of Pediatrics condemning the use of tear gas on migrant families.
"The use of tear gas on children -- including infants and toddlers in diapers -- goes against evidence-based recommendations, and threatens their short and long-term health," the statement, written by AAP President Colleen A. Kraft, reads.
"Children are uniquely vulnerable to physiological effects of chemical agents. A child's smaller size, more frequent number of breaths per minute and limited cardiovascular stress response compared to adults magnifies the harm of agents such as tear gas."
The AAP also alludes to possible psychological trauma, since children who have arrived at the border "have taken harrowing journeys."
"We must make every effort not to retraumatize them," Kraft writes.
And those long-term effects are serious
In addition to burns and respiratory problems directly after the fact, researchers have recognized several possible long-term health risks for those who have been exposed to tear gas.
"There have been many cases in which exposed people were hospitalized due to lung injuries that take quite a while to heal; days or weeks," says Jordt.
In 2012, researchers observed the health of US Army recruits during the riot control portion of their basic training. They found those who were exposed to the CS chemical "had a significantly higher risk of being diagnosed with ARI [acute respiratory illnesses] following exposure" than those who had not yet been exposed to the chemical.
Other studies that focused on children specifically found connections between tear gas exposure and serious respiratory problems. A 1972 study documented the health of an infant who was exposed to tear gas and subsequently developed a persistent case of pneumonitis, an inflammation of the walls of the lungs.