The effects of "ubiquitous" tear gas BTW
Jim Carroll

Health effects of tear gas and pepper spray:
Although the Chemical Weapons Convention (CWC) prohibits the use of tear gas and pepper spray in warfare, for domestic policing and related uses by state forces, these chemicals are allowed to be used on people and are labeled as "riot control agents." The CWC stipulates that these chemical weapons must have effects that disappear shortly after exposure, meaning no long-term health effects; however, in a number of cases, researchers have linked the use of tear gas and pepper spray to possible serious illness and death. This research echoes people's stories about tear gas and pepper spray.
In cases of the use of tear gas and pepper spray as the central element of a state offensive against people protesting in the streets and/or expressing their dissent to the conditions in which they live, people who have been assaulted with large amounts of tear gas and pepper spray, sometimes for a prolonged period of time, have reported acute and long-lasting health effects. During times like the 1987 government attack on the people of South Korea during a wave of protests where 351,000 tear gas canisters were used against demonstrators in multiple cities, or the massive use of tear gas in Quebec City in Canada in 2001 during the Free Trade Area of the Americas protests, or with the near-daily use of tear gas against people in struggle in Bahrain, Egypt, and Palestine, again in multiple cities/towns, people have reported severe health problems. In the case of Bahrain, Egypt, and Palestine, there have been many reported deaths (54 in Bahrain alone since 2011) due in some cases to tear gas canisters (the most common being CS gas) being fired at a high velocity as projectile weapons, though in other cases it is due to the exposure to the gas itself.
Experiences reported beyond the immediate effects of the tear gas include coughing, shortness of breath, and other lung-related problems (heighted in people who already have lung problems), delayed menstruation, and reports of miscarriages and stillbirths associated with the gas. These effects have also been reported in research studies, along with reports that tear gas can also cause damage to the heart and liver. In the case of pepper spray, deaths have similarly been reported (mostly in jails and prisons) due to exposure to pepper spray that is well over the "recommended" amount from the manufacturer and is used in an enclosed space and/or over prolonged periods of time. One infamous news story from 1995 reports the LA Police Department as admitting that, over a 5-year period, 61 people died while in police custody as the result of the use of pepper spray. Again, prior lung problems heighten the danger of this chemical weapon. There have been few research studies of the health effects of pepper spray, which means there is much less documentation of its longer-term effects beyond those cases of death which sometimes become public. Many continue to call for more clinical research studies about the health effects of pepper spray and tear gas.
It's important to note that in the case of tear gas, because the nature of this weapon, that in the cases of the use of the gas as a primary tool of state repression, longer-term health effects (lasting at least a week to becoming a chronic condition) were also experienced by people who were not in direct contact with police forces, which means that the health effects of tear gas can spread to people who were not at the scene at the time or were the intended target of its use.
It's also important to note that "tear gas" is not actually a gas. The active chemicals in all different kinds of tear gas and pepper spray are solid at room temperature, and need to be mixed with other chemicals in order to produce what is called an aerosol— solid particles finely dispersed in the air, similar to smoke or a cloud. They can also be dissolved in liquid solution, which is how pepper spray is commonly used. This is significant since the health effects of tear gas and pepper spray exposure can vary depending on the kind of aerosolizing agents or solvents used. For example, when silica gel is added to CS to form CS1 or CS2, the result is a stronger tear gas, which is more water resistant. Methylene chloride— a known carcinogen— was used as a solvent in the tear gas and pepper spray used against WTO protesters in Seattle in 1999. This is believed to have caused many health problems for protesters who were exposed.
Part of the problem is that the health effects of tear gas and pepper spray have not been researched thoroughly enough, and often what research has been done has been funded by or otherwise influenced by the very manufacturers who produce these weapons. One notorious example of this kind of corruption took place in Chile. On May 18, 2011, the Chilean government announced— in the wake of a study by the University of Chile which demonstrated that CS exposure may lead to miscarriages— that they would temporarily suspend the use of tear gas throughout the country. Latin America News Dispatch quotes then-Interior Minister Rodrigo Hinzpeter as saying: "[I]t seems reasonable to suspend the use of tear gas until new medical reports dispel any doubts about the appropriateness of employing these gases to confront situations of public disorder and vandalism." Fortunately for the Chilean government— and unfortunately for Chilean protesters, such as the 30,000 protesters who, a week earlier, had gathered to demonstrate against the HidroAysén hydroelectric project and been faced with tear gas— the government found exactly the evidence they were looking for, from the manufacturers themselves! The Chilean government put together a report, three days later, citing US company Combined Systems International (supplier of tear gas to the Chilean police), arguing that tear gas was safe. The report, and the lifting of the ban on tear gas, came just in time for the state to use tear gas against the next round of HidroAysén protests.
There is a similar story about how pepper spray got approved within the US for use by law enforcement. According to a report by Earth First! Journal: "[P]epper spray was originally introduced in the U.S. in the 1980s by the Postal Service as a dog repellent... The FBI endorsed it as an 'official chemical agent' in 1987 but it wasn't until 1991 that more than 3,000 local law enforcement agencies added it to their arsenals. This surge of interest hinged on a widely-circulated and influential study by FBI special agent Thomas Ward. As the FBI's chief expert on OC, Ward peddled the painful stuff like he was in a state of police-state-hallelujah.
"On February 12, 1996, we find Thomas Ward pleading guilty to a single count felony for accepting a $57,500 'kickback' from the manufacturers of Cap-Stun brand pepper spray. The second-largest company in the growing pepper spray industry, Cap-Stun also happened to be owned by Ward's very own wife, and, coincidentally, was the exact brand recommended by Ward as far back as the mid-'80s. Initially facing a $250,000 fine and five years in prison, Ward got off with two months in prison and three years probation. The FBI responded to his conviction by proclaiming it would continue using Cap-Stun since it was 'unaware of any basis for finding that pepper spray is not...safe and effective.' Ward's corrupt study is still cited today as justification for use of OC. Yet in Ottawa, Ontario; Berkeley, California; and Tucson, Arizona; police departments have chosen to stop using pepper spray due to the controversy (and costly lawsuits) it brings with it."
In other words, these so-called "non-lethal weapons" are insufficiently researched, and the research that is out there is often pushed by the companies manufacturing the weapons in the first place. What little research there is that is not sponsored by the manufacturers themselves is often done against great odds, and it generally takes a mass deployment of tear gas on the part of a state for researchers to be able to conduct such research. For instance, two landmark studies which have been done on the longterm impact of tear gas exposure, both by the group Physicians for Human Rights, were done during or in the aftermath of uprisings. The first was the 1987 uprising in South Korea. The second is the recent and ongoing uprising in Bahrain. In the 1987 report, after outlining some of the vital research which needed to take place, the NGO concluded that there "is considerable evidence that these essential studies cannot be undertaken in South Korea today. The government has not allowed research by responsible medical investigators of this problem and has refused to identify for health professionals the chemical compounds it is using, thereby blocking essential medical studies and proper treatment." In the 2012 Bahrain report...
http://facingteargas.org/bp/38/health-effects