A new Greenpeace report warns radioactive tritium from nuclear power plants in Ontario is being released into the Great Lakes and could be harmful to residents.

The report, which was released Tuesday, suggests the tritium is being released from plants in Pickering, Bruce and Darlington.

The environmental group is urging pregnant mothers and children under the age of six to avoid coming within 10 kilometres of nuclear power plants.

Study author Ian Fairlie says the tritium can become imbedded in human cells once it binds with water.

"The main conclusion of this report is that tritium is more hazardous than we think," Fairlie said during a press conference on Tuesday.

"My concern as a scientist is that given that fact, and given the very large emissions and discharges of tritium from Canadian nuclear facilities, that there may be adverse health effects in the areas nearby and that causes me great concern."

Shawn-Patrick Stencil of Greenpeace says Canada has some of the most lax standards on tritium emissions in the world.

"There is an urgent need to modernize our radiation protection standards. The government should be acting to protect the health of Ontarians by directing OPG and Bruce Power to reduce and eventually eliminate tritium emissions," Stencil said during the press conference.

Ontario Power Generation says it meets or exceeds all standards and requirements set out by Canada's nuclear regulators.

OPG says it also tests the water around its nuclear plants on a regular basis.

With files from the Canadian Press