PITTSBURGH -- Tear gas is used as crowd control. It was used at the WTO protests in Seattle in 1999.

Pittsburgh Police aren’t saying if officers will use it during G-20 protests, but if it is used , it can cause severe symptoms.

According to doctors at Allegheny General Hospital, it could cause more than just eye and throat irritation.

Fred Harchelroad, an emergency physician at AGH said, “Anyone who has an underlying condition whether its asthma or COPD could be at risk for worsening of those symptoms.”

If you wear contact lenses you could be in for more trouble.

Harchelroad said,” So if people are wearing contact lenses it can sort of penetrate through the lens and be on the eye surface being held there with a contact lens and can cause a chemical burn to the eye.”

AGH said it will have extra trauma personnel on duty during the G-20 summit.