There's a new radiation symbol that's been introduced by the ISO and IAEA which is meant to alert people that whatever they see this symbol on is a potentially lethal source of radiation. The rationale behind developing the new symbol is that while the old symbol marked the presence of radiation, it didn't provide any indication as to how dangerous the source might be. The new symbol with the addition of the skull and cross bones should definitely indicate to everyone that the source marked by the symbol is dangerous.
From the IAEA press release:
With radiating waves, a skull and crossbones and a running person, a new ionizing radiation warning symbol is being introduced to supplement the traditional international symbol for radiation, the three cornered trefoil.
The new symbol is aimed at alerting anyone, anywhere to the potential dangers of being close to a large source of ionizing radiation, the result of a five-year project conducted in 11 countries around the world. The symbol was tested with different population groups - mixed ages, varying educational backgrounds, male and female - to ensure that its message of "danger - stay away" was crystal clear and understood by all.
It's a decidedly scarier looking symbol than the classic yellow/magenta radiation symbol (right), which is probably a good thing considering the class of radioactive materials the new symbol is meant to warn people about. The new symbol is meant to be used on what the IAEA classifies as Category 1, 2 or 3 sources. These are the kinds of sources that nobody really wants to be around when they're shielded (although perfectly safe to be around when properly shielded), and definitely not when they're unshielded. Category 1 sources include RTG sources, irradiators used in sterilizers and teletherapy sources. They contain activities in the TBq (tera-Becquerel) or MCi (mega-Curie) amounts. Even brief exposure to these sources would probably be fatal in a matter of days or weeks. Category 2 sources cover industrial radiography sources and usually have activities in the high GBq (a few hundred Ci) range. Certainly less lethal, but still not something you want to be around for any length of time. Category 3 sources include calibration sources and sources for gauges and well logging.and have activities in the low GBq (a few Ci) range.
Fortunately, I will never have to see the new symbol because the activities I'm around are in the MBq (mCi) range. And if I ever do see the new symbol, I'm definitely not sticking around.