"The majority of scientific literature related to radiofrequency radiation stems from cell phone studies. There is strong evidence that people who use a cell phone held directly to their ear for more than 10 years are at significantly increased risk of developing gliomas of the brain and acoustic neuromas of the auditory nerve."
"Smart meters and cell phones occupy similar frequency bands of the electromagnetic spectrum, meaning that cell phone research can apply to smart meter radiofrequency radiation. Smart meter radiofrequency radiation consists of frequent very intense but very brief pulses throughout the day. Because smart meter exposure is over a 24 hour period, it can be very prolonged. Pulses can average 9,600 times a day... and because there is building evidence that the sharp high-intensity pulses are particularly harmful, the cell phone study findings are applicable when discussing adverse health impacts from smart meters."
"While the strongest evidence for hazards coming from radiofrequency radiation is for cancer, there is a growing body of evidence that some people develop a condition called electromagnetic hypersensitivity. "
"These individuals respond to being in the presence of radiofrequency radiation with a variety of symptoms including headaches...."
"There is absolutely no safe level of exposure established for radiofrequency radiation."
Speaking of "burden of proof," I've come across a couple of new websites with more scientific studies on radiofrequency radiation: