Occupational canine hazards

A reader writes:

I love the Australian expression "blind as a welder's dog". [Meaning blind drunk, not unable to see; example usage here. -Dan]

I don't hang out with a lot of welders, though. Do they actually tend to have blind pets? Has the RSPCA had something to say about this?


Nugget the dog
Nugget, here, is actually a plumber's dog, not a welder's. And he's not blind in either of his mismatched eyes.

Arc welding is the most common kind today (well, if you don't count the resistance welding that I think is now mainly done by robots), and also the worst for the eyes. It produces a lot of light, including very strong ultraviolet light in the dangerous UVB and UVC bands. (UVB is what gives you sunburn; UVC is even worse, but the earth's atmosphere fortunately absorbs functionally all solar UVC. Ordinary "blacklight" ultraviolet lights produce only the close-to-visible UVA light, which is almost entirely harmless.)

You don't just need eye protection when you arc-weld; you need all of your skin covered too, partly to avoid burns from flying bits of hot metal, but mainly to avoid getting severe sunburn surprisingly quickly.

Gas welding is a bit less risky for the eyes, but it's still very bright and it still makes plenty of UV. So you need eye protection for that too, unless you're welding caveman style, where you line everything up and then close your eyes and use the Force to guide you.

And yes, hard-ultraviolet light exposure can blind you. Any light - including invisible infrared - that's bright enough can damage the retina, essentially by simply heating it up (I ramble on about this at some length in this old laser review). UV light can also directly damage tissue, though, which is what causes sunburn.

Invisible light, like UV and infrared, is particularly dangerous. The brain can't tell it's there, and so won't activate the "blink reflex" or contract the pupils.

Usually, however, acute hard-UV exposure doesn't do any readily measurable permanent damage. Instead, it gives you photokeratitis, essentially sunburn of the surface of the eye. Photokeratitis, like regular sunburn, doesn't show its symptoms until some hours after the exposure, so you can give yourself a big old dose of it without noticing. And it's extremely unpleasant; it feels not unlike having sand in your eyes, but that feeling can go on for days.

On the plus side, photokeratitis makes an excellent wake-up call for people who've not been protecting their eyes from hard UV, whether it's from welding or ordinary sunlight (or sunlight plus reflected sunlight from snow; acute "snowblindness" is photokeratitis). Better a day or three of misery than no warning at all until you suddenly notice you can't read any more.

It's quite easy to damage your retinas severely without even knowing you're doing it, because the brain is very good at plastering over holes in retinal response. Normal eyes come from the factory with one built in scotoma, the "physiological blind spot", but you can only detect it indirectly. Your brain will perfectly happily cover over other blind spots, too, and you won't even know until you start, say, running your car into people because you really and truly didn't see them.

So, what of welders' pets, presuming they don't just leave them tied up in the back of the ute?

Well, on balance, I think they're pretty safe. Dogs can get photokeratitis just like humans, and probably won't connect the pain with the light that caused it, or even make it obvious that they're suffering. So if a dog habitually hangs around near its owner and checks out what he or she is doing, and he or she is making dangerously bright light, it's perfectly possible for the dog to end up with severely impaired vision.

But the light from welding isn't deadly pure invisible UV or IR. It's very obviously very bright, not unlike the sun. And dogs are not known for staring at the sun until they go blind.

(Almost nobody voluntarily looks at the weld they're making without some kind of eye protection; the main problem arises when welders use eye protection that isn't good enough, attenuating visible wavelengths well enough to make the weld viewable, but letting through too much UV and IR.)

Distance can also make a big difference. The reason why the light from welding is so very dangerous to the welder is that it is, of necessity, right there at arm's length in front of you. Get even a short distance further away and the inverse-square law will help you out.

Maybe it's more of a problem than I think, though. Noticing that your dog is suffering increasing retinal damage is even harder than noticing that it's happening to you. Perhaps the typical welder's dog actually is half-blind or worse, but the only obvious evidence of this is that he now keeps losing the stick he's meant to be fetching.

Alice the dog

Alice, here, isn't any kind of tradesman's dog, but she does have lousy eyesight, even when she's not obscuring it as here depicted.

Alice the dog

Fortunately, this doesn't seem to impact her lifestyle at all.

4 Responses to “Occupational canine hazards”

  1. uncyspam Says:

    I'm a keen amateur welder, and I have two dogs. While they are often in the garage when I'm doing just about anything else, I always make sure to lock them out when I'm welding... but not because of this, mainly because I managed to set one of them (slightly) on fire from the sparks from using a MIG. I've set myself on (slightly) on fire a number of times as well, but I can't lock myself out of the room while I weld...

    Anyway, kind of glad I do lock them out, as I've never really considered that this could be an issue... I've never heard the saying either, but I get the feeling its going to be in regular use now :D

  2. TwoHedWlf Says:

    I swear, I only slightly set my dog on fire. Hahaha

  3. cfuse Says:

    Whilst being blind isn't ideal for dogs, it's less of the handicap that we think it would be (based on our own heavy reliance on sight). Dogs olfaction and hearing are vastly superior to ours and form a larger contribution of their senses as a result.

    Also, poor (slightly) ignited doggy. That is hilarious.

  4. RichVR Says:

    "Never pet a burning dog."

    Guess where that's from?

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