Analysis of information sources in references of the Wikipedia article "美國鐳企業" in Chinese language version.
It was not until the early 1920s, after the first cancer deaths of watch-dial painters at the United States Radium Corporation in East Orange, N.J., that medical authorities began to realize that radium, in even the most minute amounts, was extremely dangerous and long-lasting. Workers had been instructed to twirl their paint brushes in their mouths to get a fine point. As a result, some victims ingested so much radium that their graves still cause Geiger-counter needles to jump.
It was not until the early 1920s, after the first cancer deaths of watch-dial painters at the United States Radium Corporation in East Orange, N.J., that medical authorities began to realize that radium, in even the most minute amounts, was extremely dangerous and long-lasting. Workers had been instructed to twirl their paint brushes in their mouths to get a fine point. As a result, some victims ingested so much radium that their graves still cause Geiger-counter needles to jump.