At a Philadelphia City Hall news conference on January 21, they pointed to federal statistics showing that of 18 U.S. counties with the highest rates, 6 are in eastern Pennsylvania. That's - the area that has the highest concentration of nuclear reactors in the country.
Activists say too much radiation - particularly radioactive iodine - is coming from those plants.
Radiation is a well-known risk factor for thyroid cancer. Activists and thyroid cancer survivors are calling for more research.
"We have often discussed the possible sources of our cancer," said Suzanne Litzenberger. "Nuclear power plants have often come up in our conversations as well as other environmental factors. It would put our minds to ease to at least know why this happened, and discover possible ways to prevent it in the future."
Exelon, the operator of Limerick and other nuclear plants, says many past studies have shown no link between the plants and thyroid cancer. They say there's been no increase in the cancer among plant workers.
