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SANTIAGO – A scientific analysis commissioned by El Salvador hospital and released by Universidad de Chile found that rubber bullets used by police in Chile contained only 20% rubber. Ceramic compounds such silica and barium sulfate and metal compounds such as lead made up the other 80%. As such, the bullets are much harder and potentially more harmful.

The sheer number of injuries from firearms related crowd control during the recent civil unrest in Chile has caused concerns outside the country. Medical experts report that more than 200 protestors have suffered eye injuries or blinding from the use of tear gas and rubber bullets. The health ministry late last week also promised extra funding to deal with over 10,000 trauma cases. The Chilean Society of Ophthalmology (SOCHIOF) said of the over 200 people with eye injuries, 30% will remain with one eye completely blinded for life. The society’s president, Dennis Cortés, also indicated that the number of eye related injuries is unprecedented throughout the world.

This widespread observation of both eye injuries and skin penetration prompted the El Salvador hospital to commission a report into the composition of rubber bullets. They extracted the rubber bullets from victims and sent the samples to Universidad de Chile for analysis. A team led by Viviana Meruane, director of the Engineering Department, performed density, load content, FTIR spectroscopy analysis, differential thermal analysis and Scanning Electron Microscope analysis. On Saturday, the team released a report with the results.

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The Report on Rubber Bullets

Perhaps the most alarming finding from the report is that the hardness of the bullets used is 96.5 on the Shore A scale which implies a hardness comparable to a skateboard wheel, far exceeding the hardness level of rubber. For comparison, the hardness of a rubber tire on the Shore A scale is between 50-70. Meruane said because the bullets are harder than rubber they can produce more damage and penetrate the body. She added a rubber ball should bounce off, causing pain and a bruise, but never penetrate the body.

The report also explains that 80% of the composition of the bullets is made up of compounds other than rubber. The ceramic element silica, which is the main component of glass, contributes to generating the hardness of the bullets. The metal compound lead gives the bullets more mass. It is the combination of mass and hardness that allow the bullets to travel with more energy and generate more damage on impact.

Whilst this is the first report focusing on the composition of bullets specifically used in Chile, a 2017 paper published in journal The BMJ (Haar et al., 2017) investigated deaths and injuries from projectiles used in crowd control globally. The authors concluded that given the inherent inaccuracy, potential for misuse, injury, disability and death that rubber bullets are not appropriate weapons used in crowd-control settings. They also stated the need for international guidelines on the use of such weaponry.