NEW YORK - The Metropolitan Transportation Authority is expanding the use of a sterilization chemical to battle rats in the subway, but the city says it will not be used in public housing.

In 2013, the transit system participated in a six-month federally-funded trial of the bait ContraPest.

While the trial only involved a limited number of subway stations, the MTA says it will deploy the product to additional stops this year.

ContraPest is a chemical that prevents reproduction by permanently impacting female rats’ ovaries. 

NYCHA says it’s not using the bait at any of its developments.

The health department says it may do a trial with the chemical as part of a pilot program.

The DOH usually studies products for a full year before making the decision to use it.

The city currently has a Rat Reservoir program that was implemented in 2015.

Through it, more exterminators were added to help tackle areas in the city with a rodent infestation.

The city says the program results in more than a 80-percent drop in rat activity.