They used to think that ionizing radiation was not harmful and put X-ray machines in shoe stores to check foot sizes... Then people got sick and they realized it's harmful.
They also used to think that non-ionizing radiation was not harmful. Then people have gotten sick and scientists discovered that non-ionizing radiation (from powerlines, radiowaves, microwave such as cell phones and cell towers) can also damage DNA, organs, and lower people's immunitiy. It also causes infertility.
Last year, the IARC (Interntaional Agency on the Research of Cancer) of the World Health Organization classified "radiofrequency electromagnetic fields emitted from wireless communication devices" as Type 2B Possible Carcinogens to Humans. They have subsequently clarified that this classification includes not only cellphone frequency, but other similar frequencies such as WiFi, smart meters and cell base stations (cell towers) etc. If the IARC experts panel had considered the risk of such non-ionizing radiationnon-existent and that it's harmless, they would have classified it as Group 4 "Probably not carcinogenic to humans", or Group 3 "Not classifiable as to its carcinogenicity to humans". Instead they chose to make it a 2B so that we, the general public, can take heed and take precaution.
I always wondered why our governments (especially USA and Canada) are not taking more action to protect citizens (or at least issue more stern warnings like some other European countries have). Then I learned that our governments earn BILLIONS of $$$ each time they license off a portion of the radiofrequency spectrum for commercial use. It makes no monteary sense for them to associate such technology with health risks.
I don't think wireless devices will disappear any time soon, but people need to be aware of the risk and use it with proper caution (such as not putting an emtting ipad next to a child's head when they sleep...). Don't laugh. Today a parent told me that's what she does, so that the 5-year-old can listen to bedtime stories from the ipad. It's not the parent's fault.