Some time ago, protests, demonstrations and riots triggered by the death of African-American George Floyd in Minnesota appeared in many parts of the United States and attracted worldwide attention.

Riot control agents such as tear gas and pepper spray were widely used by police across the United States to disperse protesters. This has raised concerns that riot control agents could exacerbate the spread of the coronavirus amid the coronavirus pandemic in the United States. C&EN, a subsidiary of the American Chemical Society, made a special report on this. [1]

Tear gas, also known as tear gas, was used in World War II and is now widely used in riot control. It is a kind of riot control agent. At present, the anti-riot agents used in hand-held jet self-defense devices at home and abroad mainly include chloroacetophenone (CN), o-chlorobenzylmalononitrile (CS), capsaicin (OC), and piperine. 2-Chlorobenzalmalononitrile (CS, 2-chlorobenzalmalononitrile) has gradually replaced the old tear gas chemical chloroacetophenone due to its low toxicity and high potency.

OC is an oily extract extracted from the pepper plant, the main active ingredient in pepper spray. Weapons manufacturers emulsify it in water and propylene glycol, or dissolve it in organic solvents to make pepper spray. OC extract is mainly composed of capsaicin, a compound that gives spicy food its spiciness. OC Pepper Spray has a spiciness level of 2,000,000 spiciness units. By comparison, Sriracha, a hot sauce popular in the US, has a spiciness of 1000-2500 spiciness units.

When pepper spray is inhaled or absorbed by the mucous membranes of the eyes or nose, substances such as capsaicin in it act on the pain receptor TRPV1 in nerve cells. TRPV1, a cation channel on these nerve cells, plays an important role in the generation and transmission of pain sensation. When TRPV1 is activated by capsaicin and other related molecules, it promotes the secretion of pro-inflammatory neuropeptides, and the resulting nerve impulses are transmitted through central fibers to the spinal cord, resulting in pain sensation.

At the scene of this riot in the United States, many cherry-sized "pepper balls" produced by PepperBall were found. The company's website claims that the pellets in this model contain 2.5 grams of a stimulant powder made up of CS, OC, or other chemical stimulants. PepperBall has a series of patented technologies. When the ball is hit, it can quickly burst and release a large amount of dust smoke to disperse the crowd.

The effects of pepper spray and tear gas tend to wear off within 30 minutes without any medical attention, Marc Michael Blum, founder of Blum Scientific Services, an expert on chemical weapons, said in an interview. There's no denying that pepper spray can stimulate inflammation in the lungs, which can be dangerous for people with breathing problems. [1]

These chemicals work by irritating the mucous membranes of the eyes, nose and throat. They can make people cough, sneeze, and remove masks when trying to improve breathing. There are no specific studies on tear gas and COVID-19, though. But a few years ago, Joseph Hout of the U.S. military conducted a study of 6,723 soldiers exposed to riot control agents. It found a link between soldiers being diagnosed with acute respiratory illness and exposure to riot control agents [2]. Joseph Hout believes that the use of riot control agents increases the damage of people's respiratory mucosa, which will increase the possibility of protesters being infected with the new coronavirus. More medical scientists have pointed out that those who came to help those injured by the riot control agent may have been in close contact with people who have been infected with the virus and who are coughing up infectious particles. In addition, those who are not yet infected may be at greater risk of becoming ill due to irritation of the respiratory tract. [3]

As for the racial conflicts behind the incident and the various performances of the US government in the new crown epidemic, I don't want to comment too much. Just one more nagging, my friends who are still in the laboratory, I know that you have silently drawn the synthetic route of the above two substances, but please do not synthesize them illegally.