NORTH ST. LOUIS COUNTY, Mo. — A study released Wednesday by the World Health Organization said long-term exposure to radiation — even low levels — can dramatically increase the risk of dying from cancer.

Carl Chappell lost his 44-year-old son Steven to appendix cancer three months ago. CBS News talked with him and six of his neighbors, all of whom either had cancer or lost a parent or child to it.

They all grew up in North St. Louis County, where radioactive material left over from America’s nuclear weapons program was stored — thousands of dirty barrels — near a creek than ran alongside their playgrounds and backyards.

Using social media, the neighbors said they’ve documented more than 2,700 cases of cancer, auto-immune diseases and tumors in their area.

“They’re not statistics and they’re not numbers,” Mary Oscko, who has stage 4 lung cancer, told CBS News. “They were my neighbors.”

Currently, the Army Corps of Engineers lists 24 other sites in 10 states with low-level radioactive contamination that they are in the process of cleaning up. There are three other contaminated sites still under consideration for clean up.

A former chemical processing plant in Queens, New York is one of them. Radiation barriers were installed as a “band-aid” solution in 2013.

Michael Feldmann with the Army Corps of Engineers says the cleanup moves slowly for a reason.

“In general, there are things that we need to move at the pace we are performing in order to protect the health and environment of the area,” Feldmann said.

Dr. Fasial Kahn is the director of public health in St. Louis County.

“Some disasters unfold slowly over time, and their true nature and extent and severity only becomes clear in terms of human cost once you start counting people around you,” Kahn said.

In North St. Louis County, neighbors have a list to keep track of who’s gotten sick — including 21 people who lived on the same street.

The residents told CBS News they believe they had long-term exposure to the low level contamination, a type of prolonged exposure that has never been studied.