Replacing the light bulbs on city streets with LED lights might not be such a bright idea after all, says Montreal Mayor Denis Coderre.

The city planned to spend $110 million to replace 132,000 street lamps – but the energy savings would mean the lights would pay for themselves within eight years.

The problem is LED lights have a dark side: many emit blue light which mimics sunlight, suppressing the body's ability to secrete melatonin.

A study by the American Medical Association suggests blue light may raise the risk of distracted driving as well as conditions including diabetes, cardiovascular disease and cancer.

“We see LED lighting as a potential health problem,” said Dr. Andrew Gurman, president of the American Medical Association. “People have sleep disorders, which can lead to all sorts of problems when they're exposed to a lot of blue light."

Last spring, Coderre asked Montreal Public Health to study the risks of LED lights.

Its report wasn't nearly as alarming.

“We found there was minimal increase in blue light for a pedestrian,” said toxicologist Louis-Francois Tetrault in December. “The amount of light is three times less than what they experience inside their home.”

The mayor said he then contacted some researchers at Sherbrooke University, some of whom were taken aback by the report by Montreal Public Health.

“Most of the publications they cite in this report are associated with a research centre which is financed by the industry,” explained Martin Aube of Sherbrooke CEGEP’s department of physics.

Coderre said he's concerned. Asked if he'll cancel the LED plan, he said: “I'm not there yet, but I'm not far.”

“We're glad he's reconsidering,” said Projet Montreal Leader Valerie Plante, who said her party wants the mayor to consider a different type of LED light, which still saves money but emits less blue light.

“If you're in a very residential sector, it should be lower and if you’re in the business sector, maybe it should be different,” she said.

The mayor said he needs more time to consider the options and plans to make what he calls “an enlightened decision” next week.