Chips of lead paint are falling off hundreds of bridges in Connecticut at such a rate that the state Department of Transportation has put out an alert to municipalities and intends to hire contractors to clean it up. “Bridge structures statewide have been experiencing a sudden, unexpected release of lead-based paint chips, which is believed to be related to the recent extreme swings in temperature,” said the DOT alert first issued to its own employees on Feb. 17. The DOT’s bridge maintenance unit spent last weekend inspecting more than 2,100 bridges across the state and determined that lead paint was cracking and falling off hundreds of them. It wasn’t clear Thursday night how many Connecticut bridges were painted with lead paint or for how long that paint type has been used.