Through social media alone, Squires said he has found at least 35 people who were diagnosed with brain tumors and lived for an extended time within about 2 or 3 miles of the National Fireworks Co. site, where crews are now working to unearth unexploded ordnance buried decades ago. Many of these cases involve people diagnosed as young adults who lived near Factory or Forge ponds or the Drinkwater River.

The number of new cases of brain and other nervous system cancers among the general population is about 6.4 per 100,000 people each year, according to the National Cancer Institute, and a 2005 report estimated about 2,014 people lived within a 1-mile radius of the site based on data from the late 1990s. Squires said based on that data, there should be maybe one person diagnosed with a brain tumor in the area around the fireworks site, not dozens…

A variety of heavy metals, including mercury, were found in the soil and water around the former factory, setting off a decadeslong effort to clean up 140 acres between King and Winter streets. While the contamination was measured at twice the threshold for earning Superfund status — a federal program that prioritizes and funds the cleanup of hazardous sites — town officials asked the state to oversee the cleanup to avoid the federal process and stigma that came with it.