Chicago's new rat control approach is poison that makes them infertile

Chicago has tried just about everything to control a burgeoning rat population fueled by a construction boom and a mild winter. None of it has worked in a city seemingly overrun by the rodents.

Now, City Hall is trying something old and something new: a poison designed to make rats infertile and dry-ice that produced promising results in parks and medians before the city was forced to stop the rat-suffocation experiment after learning the dry ice had not been approved by the U.S. Environmental Protection Agency.

The poison is called Contrapest. It will be tested for six months at a waste transfer station at 34th and Lawndale, where 25 bait boxes will be installed, each equipped with feeding tubes that encourage rats to take poisonous bait.

If it works as advertised - by rendering rats unable to breed - the poison could become a "regular method used in other enclosed and contained areas" that serve as breeding grounds for rats.

For more, check chicago.suntimes.com.