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Tear Gas

What is tear gas?

Tear gas is a term used to refer to several different riot control agents that temporarily constrain people by causing irritation to the eyes, mouth, throat, lungs, and skin. Tear gas effects usually last 15-30 minutes after a person has left the exposure area and cleaned off. Examples of tear gas chemicals include chlorobenzylidenemalononitrile (CS) and oleoresin capsicum (OC; pepper spray). 

Learn more about the properties of common tear gas chemicals:

Does DEQ have regulatory authority over the use of tear gas?

No, DEQ does not have regulatory authority over the use of tear gas. However, DEQ does regulate the City of Portland through its stormwater permit, which ensures that substances washed into city storm drains that flow to the Willamette River don't have a harmful impact on plants and animals.

On July 30, 2020, DEQ sent a letter to the Portland Bureau of Environmental Services requesting that they prepare a sampling plan and test for specific contaminants after the first rainfall.

DEQ does not have this same regulatory authority for air quality since there is not permit associated with the deployment of tear gas.

What is the status of the stormwater sampling?

The Portland Bureau of Environmental Services, which manages the City of Portland's municipal stormwater permit, collected samples at stormwater outfalls in response to DEQ's request on July 30, 2020. BES also collected samples from the storm drains they sampled before cleaning them out.

BES provided the stormwater report to DEQ on Sept. 9, 2020. BES delivered the report on time (two weeks from the date of receiving the results) and complete with the information DEQ requested. The levels detected in stormwater are not high enough to cause immediate harm to human health.

DEQ staff in the Stormwater Program and at the Lab will be evaluating this report over the course of the next several weeks. DEQ will be working with the City to determine the next steps to ensure that their stormwater protects the Willamette River.  

What are the health impacts of tear gas?

To learn more about the potential health impacts from tear gas, go to the Oregon Health Authority's webpage on tear gas. You can also reach out to their Environmental Health Assessment Program at


Media inquiries  
Susan Mills, 503-229-5579

Stormwater Program   
Christine Svetkovich, 503-229-6991