Sure, but in Goiania (and in the similar accident in Samut Prakan), the people involved didn't disregard any warnings, it just didn't occur to them at all that the source might be dangerous. This also led to a delayed response, because people were getting sick but had no idea what might be causing it it. Putting an extra red sticker on the dangerous goods will not in itself keep spent nuclear reactor fuel safe for 10,000 years, but it's at least a good start. :)