The Portland Police Bureau deployed tear gas munitions an estimated 96 times between May 29 and July 4, according to a data analysis conducted by a Portland State University graduate student.

The data shows that on some nights, Portland police used CS gas more than a dozen times: 16 times on May 30, 15 times on the evening of May 31 and early morning of June 1, and 22 times on June 22.

The data set also includes the time at which police deployed tear gas and the latitude and longitude at which they were located. This map, which illustrates police's use of tear gas over the six-week period, shows that it was deployed primarily in the region surrounding the Multnomah County Justice Center and the Mark O. Hatfield federal courthouse, where protesters typically gather.

(Portland State University)
(Portland State University)

It wasn't immediately clear how the researcher determined the locations where tear gas was deployed.

A Portland Police Bureau spokesman said in an email to WW that the deployment of CS gas is a "force event."

"The Bureau's commitment to public safety includes ensuring the welfare of members of the public, its officers and professional staff, with an emphasis on the sanctity of life and policing with respect," the spokesman wrote. "The Portland Police Bureau recognizes that this commitment may require members to use force."

The spokesman added that officers are required to write a report about every use of force event, and also complete a Force Data Collection Report "that includes a full accounting of the force applied and the justification for it."

The numbers aren't entirely surprising. A KATU-TV investigation in June revealed that PPB spent more than $45,000 on riot control agents (like tear gas), munitions and respirators for gas masks.

To date, little is known about the effects of tear gas on the human body and the environment. Local research groups, including Kaiser Permanente, have commissioned studies to determine such impacts.