Cancer and health damage
Radiofrequency electromagnetic radiation from all sources was designated a possible carcinogen in 2011 by the WHO International Agency for Research on Cancer. International scientists have called for reclassification at least to "probable carcinogen". In December, after reviewing research since 2011, researchers Lennart Hardell and Michael Carlberg called for RF-EMF to be classified as a carcinogen. In 2016, the NIH National Toxicology Program released partial results showing that after only two years of exposure to 2G radiation, 1 in 12 male rats studied developed malignant brain tumors, malignant heart tumors and precancerous lesions. The NTP released these final peer-reviewed results ahead of the rest of the study in order to alert the public.
The harm is more than cancer, however. DNA and genetic damage; changes in the blood including red blood cell clumping; breaches in the blood-brain barrier, with links to Alzheimer's, stroke, MS and auto-immune diseases; neurological damage; sperm damage and sperm rafting (not a new Olympic sport); infertility; heart-rhythm disturbances; cataracts; impacts on blood-sugar regulation, blood pressure, the immune system, and cognition; cellular-stress responses; and the production of free radicals are a few of the effects from short-term, long-term, and cumulative RF-EMF exposure to humans and other species. 
Children are extremely vulnerable due to their developing neurological and immune systems, and the Russian National Committee on Non-Ionizing Radiation Protection released an international appeal in 2008, warning of serious health consequences from children's use of cell phones.
In 2015, the Canadian Parliament held three days of hearings with experts warning of a public-health crisis and that action was urgently needed.
After a study of firefighters living under cell towers found severe, sometimes immediate impacts on cognitive function, the International Association of Firefighters passed a resolution calling for new biologically based exposure limits and a moratorium on cell towers on fire houses. Firefighters also received an exemption from 4G/5G cell towers on their facilities in California Senate Bill 649 last year.
Former president of Microsoft Canada Frank Clegg calls wireless radiation "our biggest modern health threat". Though other countries have taken steps to limit exposures, wireless-radiation hazards are ignored by the FCC, Health Canada, and many other regulatory agencies. American exposure limits are some of the highest in the world and are based only on thermal (heating) effects. These standards have been criticized even from within the U.S. government.
The FCC stalled a proceeding (13-84) in 2013 to re-evaluate RF-exposure limits, meanwhile rushing out new wireless products, auctioning off more spectrum, deregulating the industry, and eliminating ("streamlining") local governments' regulatory authority.