A rapid rail line to Pearson International Airport is going to expose more than 300,000 Torontonians to "toxic fumes" and "unnecessary health risks" unless the province kicks in the extra cash to have its trains electrified, says NDP Leader Andrea Horwath.

Horwath made the comments during a Clean Trains Coalition rally held along the proposed route Saturday afternoon, saying diesel trains would put too many people at risk.

"The medical officer of health has said very clearly that this is not good for the health of these citizens and the bottom line is this train can be electrified from day one," Horwath told CP24. "If you are going to do something do it right the first time. Don't do a diesel train now and then at some point down the road electrify it."

The line, which will tie in with GO Transit's Georgetown South Project, will begin at Union Station and terminate at Pearson's Terminal 1. Constuction is expected to begin in the spring at a cost of $128.6 million with the line expected to be fully operational in time for the 2015 Pan American Games.

Metrolinx is responsible for the project.

"We want Dalton McGuinty to listen to our community and to listen to the will of city council, and to build electric trains along this line, to put in stops that will to tie into our transit system locally and give people an affordable accessible option that won't make people sick and pollute our environment," NDP MPP Jonah Schein told CP24 Saturday afternoon.