Residents living around the epicenter of the protests in Chile's capital have been suffering from nose bleeds, conjunctivitis, dermatitis and acute coughing brought on by the police use of tear gas.
Karen Mariángel lives across the street from Plaza Italia, the focal point of the demonstrations in Santiago.
She and her daughters stay inside from 5 pm each day and she makes sure to lock the doors, close the window and turn on the air purifiers as protesters and police descend on the square.
"I had bronchitis for a week and my husband has had a cough that won't shift," she told Efe, discussing the non-lethal chemical weapon, which is in common usage around the world, from Hong Kong to Iraq.
"The problem is not the bombs themselves, but their excessive, disproportionate and frequent use," she said.
The defining compound in tear gas is chlorobenzylidene malononitrile, or simply CS gas.
It causes irritation of the eyes, nose, respiratory tract and skin but prolonged exposure can trigger more serious health risks, according to José Miguel Bernucci, the secretary of Chile's national medical association.
"People with chronic illness, both pulmonary and cardiovascular, are more at risk and may suffer acute respiratory failure, as do pregnant women," he said.
CS gas particles stick to asphalt and the walls of buildings, which, in combination with the dry climate, heat and the dust coating every corner of the neighborhood due to the battles between police and protesters, results in a kind of mist that makes it difficult to breathe.
Experts estimate that an exploding tear gas cannister throws its content over a radius of 300 meters squared and remains traceable for five days.
"My daughters have already learned that they have to clean themselves with bicarbonate when they return from the park and throw all their clothes in the wash," Mariángel said.
For Manuel Benítez, an 82-year-old resident returning from one of the shops still open in the area, the situation is "unbearable."
"The people who were able to leave have left. We cannot because my wife is quite sick and can't move," he told Efe.
A large cloth banner at the opening of Juana de Lestonnac street, in front of Bustamante Park, alerts police to the presence of young people and families in the housing block.
It is one of the initiatives from the neighborhood group "No More Tear Gas," who next week plan to go to the courts with an appeal to limit the police use of tear gas in the area, as has happened in the southern city of Concepcion following similar civic action.
"I do not understand how the government can spend so much on gas and not on giving it to the poor that they are starving," Magaly Matus, 80, told Efe.
Despite the disruption to their daily lives, most of the residents here support the protests.
The demonstrations first erupted last month in opposition to a planned hike in metro ticket prices before it grew into a general clamor against the conservative government of President Sebastián Piñera and the unequal economic model adopted during the dictatorship of Augusto Pinochet (1973-1990).
"It is a very bipolar situation. On the one hand, we are seeing people suffer from toxic substances but on the other, there is the joy of knowing that this is a historical moment that we never thought was going to come," María Angelica Ovalle told Efe.
The residents of downtown Santiago are also aware that the tear gas is the "lesser evil" in the protests when compared to the 23 deaths and thousands of injuries in the unrest.
Almost 200 people have suffered serious damage to their eyes as a result of police firing objects like rubber bullets.
"There are much worse situations, I have not had to see my daughter lose an eye," Ovalle said.EFE