Thanks for your question.  In your asking it, I assume that tear gas has recently been employed in your neighborhood due to various forms of disturbance.

I found very little in the way of scientific-based research on this important matter.  In part, the answer to your question depends upon the composition of the tear gas.  The most common compound found in tear gas is o-chlorobenzylidene malononitrile.  Fortunately, this compound breaks down rapidly when it contacts moisture and is largely removed from the air by wet/dry deposition close to where it’s released.  Some reports indicate that possible soil contamination from this compound would be extremely low if your garden was more than two blocks removed from where the tear gas had been employed.

I would suggest that you contact the Minnesota Department of Agriculture and the Minnesota Department of Health for additional information.:

https://www.mda.state.mn.us/

https://www.health.state.mn.us/people/foodsafety/index.html

Finally, it may be worthwhile to contact the University of Minnesota Soil Testing Laboratory for their opinion:

https://soiltest.cfans.umn.edu/testing-services/lawn-garden

Good luck. Thanks for consulting us.