Montreal is preparing to change more than 100,000 street lights for high-efficiency LEDs, but there are concerns about the effect this will have on people.

At the city's request, the Quebec public health department looked into the matter, paying particular attention to the colour spectrum used by the lights.

The white lights have a colour-temperature of 4,000 K which is on the cool, blue end of the spectrum as opposed to warm, or yellowish white lights.

That has some people worried that excessive exposure to street lights could interfere with a person's circadian rhythm and make it harder for them to fall asleep at night.

Robert Dick, a professor at the University of Ottawa who founded the Canadian Light Pollution Abatement Program, said some studies have indicated possible links between blue-tinted light and obesity, anxiety, stress, and other issues.

"That's probably one of the problems with it because each one of those fields is different. It's a different medical discipline. And you have to read all these disciplines to see the general trend across the entire medical sciences," said Dick.

One of the authors of the report said the team looked at epidemiological studies of the effects of the light spectrum, and they calculated the amount of exposure to blue light in the home and on the street.

They concluded most people spend very little time under street lights and are actually exposed to three times the amount of blue light when at home.

The LED switch would cost $110 million, but would save much more than that in electricity costs over the lifespan of the LED lamps.

Ottawa and Los Angeles have already switched to LED streetlights.

The city of Montreal is analyzing the study before making a final decision.