For the past two weeks, clouds of acrid smoke have billowed through the country’s major city streets as the youth, armed only with placards and water bottles, faced a barrage of teargas canisters from the police. 

 This has raised questions about the use of teargas and other chemicals against civilians.

Teargas, despite its name, is not a gas but a pressurized powder that creates a mist when deployed. The most common form is 2-chlorobenzalmalononitrile (CS gas), first discovered by American scientists in 1928 and adopted by the U.S. Army for riot control in 1959.

Other variants include oleoresin capsicum (pepper spray), dibenzoxazepine (CR gas), and chloroacetophenone (CN gas).

While designed for crowd control, their use has become increasingly prevalent, raising concerns about potential long-term health impacts.

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Dr George Nyale, a chest specialist at The Karen Hospital, explains, "Most people recover from teargas exposure without significant lasting effects. However, repeated or high-intensity exposure, especially in enclosed spaces, can lead to more serious complications."

One of the primary concerns with teargas exposure is its effect on the respiratory system. 

"In individuals with pre-existing conditions like asthma or chronic obstructive pulmonary disease, teargas can trigger severe exacerbation," Dr Nyale says. "We've seen cases where repeated exposure has led to the development of chronic bronchitis or reactive airway dysfunction syndrome (RADS)."

A study by the National Library of Medicine found that prolonged or repeated exposure to teargas could lead to persistent cough, shortness of breath, and decreased lung function in some individuals. 

While rare, cases of severe respiratory failure have been reported following intense exposure in confined spaces.

“Exposure in closed spaces increases the detrimental effects of CS. Pulmonary function deterioration and respiratory complaints might be observed several months after the cessation of exposure to CS,” read the report.

The eyes, being particularly sensitive to chemical irritants, are another area of concern.

 "Long-term exposure or close-range exposure to teargas can cause blindness due to damage to the optic nerve (traumatic optic neuropathy), bleeding (subconjunctival bleeding), cataracts (traumatic cataract), corneal erosion and chemosis (swelling of the lining of the eye)," a report by UM Surabaya University's Faculty of Medicine says.

According to Dr Ezekiel Mecha, a Senior Lecturer in the Department of Biochemistry at the University of Nairobi and a certified Global Consultant in Biorisk Management and Biosecurity, the duration and spread of tear gas depend on several factors: 

"Inside or outside closed area. It also depends on the weather conditions. In cold, humid and calm conditions it takes longer to clear unlike in opposite conditions," he says.  

The Biochemist adds that the amount of gas released also determines the clearance rate — one canister or more.  

"Tear gas can take 3 to 5 hours to clear, that again dependent on the prevailing weather conditions and how many canisters released," he says.  

He adds that in cold and calm (non-windy) and enclosed conditions, it can take several days.
If several canisters are used, it may take up to two days to clear.

Dr Mecha notes that individual reactions to tear gas vary, similar to how people respond differently to onion odours. Tear gas, being heavier than air, tends to settle on the ground unless dispersed by wind. It also adheres to materials like clothing.

"Tear gas is heavier than air, so it tends to settle on the ground unless pushed by wind," he says, "It sticks in materials like clothes."

In enclosed, cold, and calm environments, it may persist for several days. If multiple canisters are used, clearance time can extend up to 2 days.

For those affected, including non-protesters, Dr Mecha advises: 

"The idea is don't rub your eyes or wash with just water as tear gas is oil-bases, try to use milk, or water with soap, also change clothes as soon as you can as the gas is stick, move to open air, but not in the direction the wind is blowing to, from the canister point," he says.

Skin exposure to teargas can result in irritation, redness, and in severe cases, chemical burns.

Dr Saini Roop, a Consultant Dermatologist at the Kenyatta National Hospital, explains, "Most skin reactions resolve within days. However, we've seen instances of allergic contact dermatitis developing in individuals after repeated exposures, leading to chronic skin issues."

Beyond physical effects, the psychological toll of teargas exposure is gaining recognition. Elmard Rigan, a therapist at Spring Health, notes, "The terror and disorientation caused by teargas can have lasting psychological effects, particularly in individuals repeatedly exposed during protests or those with pre-existing mental health conditions."

A study published in the Turkish Journal of Psychiatry found that prolonged or repeated exposure to teargas was associated with increased rates of anxiety, depression, and symptoms of post-traumatic stress disorder (PTSD) among frequent protesters.

While human studies are limited, some animal research has raised questions about the potential reproductive effects of teargas exposure.

A study published in the journal Reproductive Toxicology found that exposure to high levels of CS gas in pregnant mice led to an increased risk of miscarriage and fetal abnormalities.

However, the Hong Kong Medical Journal states there is limited data on the effects of acute exposure to tear gas during pregnancy. 

The use of teargas in warfare was banned by the Chemical Weapons Convention of 1993, which prohibited the use of riot control agents as a method of warfare. However, its use in domestic law enforcement remains legal in many countries, including Kenya.

Human rights organisations have called for stricter regulations on teargas use.  "The potential long-term health effects underscore the need for more restrained and proportionate policing methods," states Amnesty International Kenya spokesperson Irungu Houghton.

As the smoke is yet to clear, the conversation about balancing public safety with the right to peaceful demonstration continues.