A Columbia University professor is warning the public about the negative health effects of man-made electromagnetic fields, which come out of cellphones and power lines.

Dr. Martin Blank, a professor with the school's Department of Physiology and Cellular Biophysics, compared the EMF waves to the ripples caused by dropping a pebble into a quiescent pond.

"The water doesn't move, it just carries the energy further and further out," Blank told CTV's Canada AM Wednesday.

"It's the same thing about these waves. These waves are generated in all kinds of charges that are present anywhere.

"When you get an electromagnetic field that's coming out of a power line, or it's coming out of a cellphone antenna or a cellphone tower it's going to do things to the molecules in our body."

Blank says EMFs in the environment may lead to brain tumours, Alzheimer's disease, dementia and breast cancer.

Blank, who is speaking in Toronto Wednesday on behalf of the BioInitiative Working Group, said past research has focused too much on the thermal effects of man-made EMFs.

"The heat is what everyone has focused on largely because that was an easy thing to measure," he said.

However, Blank said researchers are now able to measure biochemical changes.

"The biochemical changes occur long before there are changes in temperature," he said.

"That's why people who have focused on the thermal effects, which is the measure of the heat, have gotten the wrong answer."

He said researchers have concluded that there is no real harm because they haven't found any changes in temperature.

"That's not true, there's a lot of change going on there," Blank said.

"One of the changes we've found is the stress response. The cells themselves are telling us that they're in trouble."

In the "language of the cells," they start to make new proteins that they haven't made before and that they only make when they're in trouble.

"These stress proteins are made with all these different electromagnetic fields (EMF)," he said.

"They're made with power line EMFs, they're made with cellphone EMFs and there a clear indication that the cell senses this stuff as potentially harmful."