Photographs of welders, visors down, guns in hand with sparks flying and plumes of smoke hovering around them create a dramatic and impactful visual, but they also depict one of the biggest hazards welders and other metal workers face – the many toxic substances found in welding and associated processes.
According to MarketGlass, an organization that delivers project-focused market intelligence, expenditures related to the weld fume extraction equipment market are expected to reach $6.2 billion by 2027, which represents a near 40 percent increase from 2020. But could that be a conservative number? The answer is “yes” if OSHA changes its acceptable level of manganese to fall in line with the American Conference of Governmental Industrial Hygienists (ACGIH) science-based recommended limit, which is 250 times less than OSHA’s.
Jonathan Hale and Bob Dayringer, industrial hygienists with a combined 84 years of experience, have a vast knowledge of the toxic substances and gases created through welding and other manufacturing processes. They recently hosted an ACGIH seminar titled “Understanding and Controlling Toxic Metal Fumes from Welding and Other Processes.”
They make it clear in the seminar that it’s not just welders who are at risk because metal fumes can be generated through torch cutting, laser cutting/engraving, arc gouging, plasma cutting, and flame and metal spraying. And it’s not just the metal that creates the fumes once heat is introduced; oils, zinc oxide, paints, primers and other organics add to the toxic cocktail.
Toxic side effects
OSHA’s fact sheet on hexavalent chromium, one of the more toxic and carcinogenic substances found in weld fumes, says it affects the nose, throat and lungs. “Symptoms may
include runny nose, sneezing, coughing, itching and a burning sensation,” the sheet says, but repeated or prolonged exposure can lead to sores in the nose that lead to nosebleeds, perforations in the nasal septum, asthma symptoms and allergic skin reactions.
Another big substance to watch for is manganese, which is present in gases created through several types of welding applications and is found in base metals, rods, flux and weld wire. Prolonged exposure can cause hand tremors, sleepiness, irritability, weakness, mood change, balance disorders and facial spasms. In cases of extreme exposure to manganese, victims, usually miners and smelters, will suffer symptoms similar to Parkinson’s Disease. However, Dayringer notes that to date, welders have not shown Parkinson’s-related symptoms.
“Manganese is the new lead on steroids,” Dayringer says, adding that the ACGIH set a health-based recommendation of 0.02 mg/m as the maximum acceptable level, whereas OSHA’s is 5 mg/m. States have also set limits of their own. For instance, Michigan’s manganese level is 1 mg/m. “We’re recognizing that all things are poisonous, but we don’t agree very much on anything else.”
As for other toxins, exposure to iron oxide, another common element found in weld fumes, creates a malady called siderosis, which is a benign pneumoconiosis. Also called “dusty lung,” it can look like a cloud in X-rays, which can hide other ailments in the lung. Cadmium exposure takes a heavy toll on the kidneys while lead has a negative impact on virtually every organ in the body.
And copper and zinc exposure can cause “metal fume fever,” which is similar to influenza symptoms. Dayringer and Hale have both experienced this. Hale’s team was removing used ventilation bags at a facility when a gust of wind came up and they all unknowingly inhaled a concentrated dose of particulate.
“It happens pretty quickly,” he said of the onset of metal fume fever. “The next thing you know, you’re throwing up. It’s as sick as I’ve ever been.”
These are just a handful of the many toxic substances found in welding and associated processes, but there are ways for workers to stay safe in the environment.
A big part of Dayringer’s career involves monitoring welders and taking air samples.
“I can almost always tell you who will have the highest sample just by watching how the worker positions themself,” he says. “I know it’s not a cure-all, but when you can, try to move your head back. Try to get out of that smoke as much as you can. I’ve seen many welders who weld like they’re nearsighted and weld right on top of their work. They’ve got their head in that plume, which has 50 to 75 mg/m of particulate.”
Stick welding, Dayringer says, is always “dirtier” than MIG, but in the hierarchy of processes, MIG welding is notoriously more toxic than TIG. And that’s why Dayringer advises going with TIG whenever possible. When MIG welding is the only option, he says to use waveform versus traditional MIG, which is known to reduce the amount of weld fumes. Waveform, which is a fairly new power source technology, reduces total arc energy, which helps to control how much metal is vaporized, leading to a reduction in toxic fumes.
Finally, when it comes to the gas used in welding, Dayringer says straight CO2 creates more fumes than argon.
“You should run 20 to 25 cubic ft. of shielding gas per hour,” he says. “If you use less, you’re going to have more fumes.”
For welders who have any chance of breathing in toxins, respiratory protection is a must. Many fumes can often be blocked by wearing a simple N95 mask, but as Dayringer points out, many welders don’t want to wear them.
“The problem with respiratory protection is the welders aren’t going to wear those masks,” he says. “I’ve been there with overexposure cases and they try to get them to wear them, but the welders revolt because they’re uncomfortable and they cause fogging of the face shield and they can’t see what they are doing. If you have a beard, they don’t work well at all. The only other choice is a PAPR.”
PAPRs, or powered air purifying respirators, utilize a battery-operated blower to push contaminated air through a HEPA filter, which removes the toxic substances and supplies purified air through the faceplate.
The main reason Dayringer refers to the PAPR as the go-to protection device is because it offers 25 times the protection that the ACGIH recommends for manganese. Throughout his career, Dayringer has taken air samples from inside many welding helmets. After analyzing between 15 and 20 years of data, he found that the mean exposure level to manganese averaged 0.36 mg/m, which is 18 times the ACGIH recommendation for exposure to that toxin. A filtering facepiece, such as an N95 mask, has a protection factor of 10 times the ACGIH limit, which means it won’t be effective.
“I would love to see the feds reassess the manganese exposure limit,” he says, “but they’re so terribly slow at changing the exposure limits. It could be many, many years before we see it happen. Regardless, OSHA is tremendously out of date when they say 5 mg/m. That’s just a boatload of manganese. When the lowest recognized observable effect is 0.03 to 0.04 mg/m, it’s right there in the documentation, the threshold limit values. The studies on manganese exposure show there are all sorts of central nervous system effects.”
Aside from the fact that most welders do not want to wear a PAPR, it is also very expensive. It’s for these reasons that engineering controls, i.e., ventilation systems
implemented within the shop, are adopted. Rather than a bulky apparatus attached to the face, the best ventilation systems work stealthily in the background.
“The engineering controls where the employee doesn’t even know they’re being properly protected,” Hale says, “are the ones everyone really, really likes.”
Engineering controls have their downsides, too. For example, introducing fans in a “pollution dilution” scenario risks pulling fumes through areas where people are working. There is also the added expense found in ventilation solutions that utilize outside air, which in the winter months must be heated before being introduced to the shop, adding another layer of cost that becomes a deal breaker.
As for source extraction systems, exhaust hoods are frequently used to keep toxic substances created by welding and metal cutting from leaking out into the shop, but to be effective, they have to be placed close to the source of the contaminants. It’s up to industrial hygienists like Dayringer and Hale to determine if the hoods are performing effectively. Hale says one process they rely on is computational fluid dynamics, which is a process involving computer modeling of pollutant pathways and the analyzation of numerical data as well as data structures to solve problems related to how contaminants are captured in ventilation systems, such as hoods.
Hale makes an analogy when comparing local fume extraction solutions to general ventilation systems where the entire room is acting as a hood. Think of fumes as cattle leaving a barn. Wouldn’t it be more efficient to brand them as they’re in the chute rather than waiting until they’re spread throughout the pasture? In that sense, one of the more efficient means of capturing toxic fumes is to use a booth, which in some cases is a tent-like structure placed around the welding area. A fan (or “motivator” as industrial hygienists call them) creates air crossflow that directs fumes into hoods where MERV filters remove roughly 99-plus percent of the toxins.
The ACGIH updates its official industrial ventilation manual every three years, and Hale says one of the most important entries is found in chapter 13: Choose hood designs in the following descending order of effectiveness: enclosing hoods, vacuum nozzles, fixed slot/plenum hood on a worktable or rectangular hood fixed above a worktable, moveable hood above a worktable, moveable hood hanging freely or overhead canopy, dilution ventilation.
“The hood design we feel is the best with toxic substances is a designated weld area of the booth,” Hale says. “With weld fumes, we can use highly efficient filtration and allow the filters to pick up the fumes and safely return that air right back to the room so it doesn’t have to be heated or cooled. Booths are very effective – the back panel of it is nothing but filters. We feel like it is the most efficient, effective and cheapest way to protect workers from highly toxic fumes.”
Hale says most booths are designed with a cross-flow air ventilation rate of 100 to 150 ft./min., which is enough to carry away the fumes without disturbing the weld current and causing an improper weld. Dayringer adds that to maintain the integrity of the weld, the American Welding Society’s ventilation guide recommends that air velocities not exceed 240 ft./min. in shielded metal arc welding, 150 ft./min. in gas metal arc welding and 60 ft./min. in gas tungsten arc welding. Welders can also be positioned so the air flow whisks the fume away enough that they won’t have to wear respiratory protection.
Another source capture option that most companies producing welding equipment offer is called a high-vacuum extraction solution that is actually part of the weld gun. Due to its effectiveness and low cost, Hale refers to it as the “wave of the future.”
“With a high-vacuum system,” he says, “we’re using very small CFMs at the point of generation, which makes for a very small filtration system. The intrinsic extra amount of cost for the dust collector goes down drastically. And also, the combustible dust precautions that have to be part of the engineering controls go down at the same rate.”