In the United States, the overall cancer death rate has declined since the early 1990s. The most recent SEER Cancer Statistics Review, updated in September 2016, shows that cancer death rates decreased by:
1.8% per year among men from 2004 to 2013
1.4% per year among women from 2004 to 2013
1.4% per year among children ages 0–19 from 2009 to 2013
From https://www.cancer.gov/about-cancer/understanding/statistics. Yes, that's US only, but the US has built a lot of cellular and wifi infrastructure during that time of cancer rate decline.