Sorry if this has already been asked.
I just find it weird that something as dangerous as radiation would be associated with a color that’s usually viewed as safe (for example firemen, police, and other social workers, plus in general media) would be in the symbol for radiation?
I mean, even most warning signs I see have red or orange on them, which we associate more easily with danger, but the symbol for radiation is just, yellow. It DOES make me fairly alarmed but if I didn’t know what radiation was I don’t think I would be..
Plus with how much we usually see radiation portrayed as green wouldn’t that make more sense? (portrayed with something like orange and red too)
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Yellow is not a color traditionally associated with safety. A yellow light means caution. Driving signs and lines are often yellow to urge caution. Hell, bees are yellow and black; I’m assuming you don’t find a swarm of bees safe. Nor are firefighters or police; they are primarily found where things are going wrong, so dressing them in yellow can signal that you should be cautious.
That’s a good question, because there is an ANSI standard color system for signage, and yellow is not severe using that system.
"The ANSI signal word panels are intended to have different meanings in terms of severity and probability of the hazard:
The red DANGER panel is intended to indicate a hazardous situation that, if not avoided, will result in death or serious injury (immediate and grave danger).
The orange WARNING panel is intended to indicate a hazardous situation that, if not avoided, could result in death or serious injury
The yellow CAUTION panel indicates a hazar- dous situation that, if not avoided, could result in minor or moderate injury."
The answer to your question can be found in this article published by the Oak Ridge Associated Universities (ORAU) Museum of Radiation and Radioactivity, which begins by citing Nels Garden, onetime head of the Health Chemistry Group at the University of California Radiation Laboratory:
> The first signs printed at Berkeley had a magenta (Martin Senour Roman Violet No. 2225) symbol on a blue background. In an earlier letter written in 1948, Garden explained why this particular shade of magenta color was selected: "it was distinctive and did not conflict with any color code that we were familiar with. Another factor in its favor was its cost… The high cost will deter others from using this color promiscuously." Explaining the blue background, he said, "The use of a blue background was selected because there is very little blue color used in most of the areas where radioactive work would be carried out."
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> Garden did not like yellow as a background: "the very fact that… the high visibility yellow stands out most prominently has led to extensive use of this color and it is very common." To compensate for the lower visibility of the blue, Garden even toyed with the idea of including diagonal white stripes across the sign.
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> Despite Garden’s view to the contrary, most workers felt that a blue background was a poor choice. Blue was not supposed to be used on warning signs, and it faded, especially outdoors. The use of yellow was standardized at Oak Ridge National Lab in early 1948. At that time, Bill Ray and George Warlick, both working for K.Z. Morgan, were given the task of coming up with a more suitable warning sign, a blue background being too unacceptable. Ray traveled to Berkeley and picked up a set of their signs. Back in Oak Ridge, Ray and Warlick had their graphics people cut out the magenta symbols and staple them on cards of different colors. Outdoors, and at a distance of 20 feet, a committee selected the magenta on yellow as the best combination.
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> All sorts of variations on the Berkeley design were suggested and implemented during the 1940s and early 1950s. Especially common were signs that incorporated straight or wavy arrows between, or inside, the propeller blades. By the late 50s, ANSI standards and federal regulations had codified the version of the warning sign used today. Present regulations also permit the use of black as a substitute for magenta. In fact, black on yellow is the most common color combination outside of the U.S.
Yellow was found to be the most eye catching color. One of the first Google search results was a history of the symbol and how it changed over time.
How Are Universal Ionizing Radiation Symbols Used Around the World?
From an international perspective, it’s worth thinking about how these signs fit into a system of iconography. The yellow-and-black radiation hazard sign is part of a system defined by the International Standards Organization – ISO 7010, which built off ISO 3864. Both of these define standards for workplace safety symbols. They separate things into four categories: prohibitions, hazards, instructions and ‘safe conditions’ (there is also a fifth category for noting the presence of fire equipment, but that’s less important).
Prohibitions are things that workers should not do to avoid exposure to risk – for example, not eating and drinking in a laboratory. Instructions, meanwhile are things that workers should do to ensure their safety – e.g. wearing a hard hat. Safe conditions signal the position of things like fire exits and first aid kits, which are helpful in an accident. Finally, hazards are things that workers should be aware of when working to ensure their safety, like the presence of toxic chemicals. Radiation fits clearly into the hazard category. But that category is also in the middle level of severity. Prohibitions are much more serious than hazards, they’re things that workers absolutely shouldn’t be doing to keep them safe. As such, ISO 7010 associates prohibitions with red; safe conditions should clearly be green. This leaves yellow for hazards, and blue for instructional signs.
This might be confusing in the case of radiation, but it’s worth remembering two facts. Firstly, not every radiation source is a huge danger. Yes, some radiation sources can kill you very quickly. But for other sources, the danger is just a small increase in your chance of getting cancer. The symbol has to cover this whole range. The other factor is that the ISO 7010 system has to cover a vast array of hazards. It doesn’t just cover radiation hazards, but many other hazards a worker might face. Some of these could easily be deadly, such as explosives, but others, like barbed wire, might just be unpleasant. It doesn’t really make sense to make an exception from a consistent system for a single hazard.
Finally, we should note that yellow and black is a consistent system for hazards. It shows up in nature – bees and wasps being the obvious example. Yellow/amber shows up as a caution marker in traffic lights in daily life. The yellow and black colour scheme is also used to mark hazards elsewhere; hazard tape is consistently yellow and black, for example.
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Fun fact: green that is used to portray radiation in films and animation is not really accurate. Chernekov radiation that you see in reactors is blue.
More fun fact – it is caused by particles travelling faster than light (usually in water). Note that "faster than light" in a given medium is still slower than "C", the speed of light in a vacuum.
It’s been updated/supplemented to better convey the danger. It was decided the traditional yellow and black didn’t convey the danger, the type of danger/that it’s dangerous without direct contact, or tell the reader to leave. This is the new symbol, complete with red background, rays being emitted from the traditional radiation warning symbol, a skull and crossbones to indicate the threat of death and a person running to tell the reader to leave, now.
Yellow and black has better contrast for partially sighted people than most other color combinations, while also being distinctive enough to stand out. Same reason caution tape and such are also yellow and black.
This is actually a challenge in some parts of West Africa.
Danger/ caution signs are usually yellow because it stands out. But this colour is a symbol of prosperity in some cultures. So it attracts people rather than keeping them away.
Yellow and black have always been associated with danger. We use it on our road signs and nature had used it as a "don’t mess with me or else" warning in the evolution of species (bees, wasps and many species of harmless flies that mimic them). It only seems fitting.
> a color that’s usually viewed as safe
This is such a crazy take to me. I guess it’s a cultural thing?
Because here, yellow and black are the main warning colours.
Yellow and black are very high contrast colors, making it far more likely that someone will see the symbol even in low light or poor conditions. That’s why warning signs are frequently in yellow and black, such as road signs and hazard stripes.