Hexavalent chromium

This has to be one of the coolest types of cutting. Raw obliteration of metal.

As you know, hexavalent chromium (Cr6) is generated when the metal, chromium, is heated. Cutting this metal with a plasma torch is an easy way to heat it up quickly.  We performed air monitoring on one employee performing plasma cutting on #304 stainless. Luckily the employee was wearing a 1/2 face tight fitting respirator (and skin protection due to the body readily absorbing Cr6) and we found exposures at 36% of the exposure limits (they were within the acceptable limits). This employee was able to stand away from the cutting due to the machine he was using. He did not do this task all day and no engineering controls (ventilation) was used. 

****Caveat: Please do your own air sampling. Conditions and environment may not be similar to your environment, and they can change rapidly. One sampling event rarely indicates all conditions. We’re talking about people’s health!****Keep in mind welding safety

plasma cutting

And a close up of the cutting machine without the motor & tracks:

cutting bevel

Chromium in it’s elevated valence state, called Chromium 6, or hexavalent chromium is a known carcinogen and sensitizer. From a toxicological point of view, it has a really interesting exposure to disease path.

I’ve mentioned it before, but recently NIOSH reduced their suggested limit from 1.0 µg/m³ to 0.2 µg/m³ (80% reduction for you math wiz’es).  They base this on eye & skin irritation, respiratory damage & lung cancer. Yikes.

OSHA has listed their exposure limits, along with other’s recommended limits here.

The take-away from this reduction is the serious nature of Chromium 6. hex chrome cleaningIf you are dealing with this hazard, you should take more than just a little precaution. Even if your prior air monitoring data is below the Action & Exposure Limit, continue  to document and verify your employees are well below the regulatory & recommended limits. As you know, hexavalent chromium is a skin hazard and can be absorbed easily into your body. I would also suggest performing wipe samples (area & skin) & decontamination in areas where there is work activity with hexavalent chromium.

For most construction companies, investigate these areas:

  • welding (any stainless steel?) See this earllier post, also here.
    • And, OSHA has a new Fact sheet on welding & hexavalent chromium here.
    • Washington’s OSHA (L&I) has a great page on the hazards during welding here, including training videos. (so cool!)
  • hardfacing on equipment. See earlier post.
  • Bridge painting – (or painting with chromates) OSHA’s new safety bulletin is here.
  • Electroplating – OSHA’s safety bulletin is here.
  • Anytime you heat, or work with chromate painted surfaces.
  • Portland cement when working with it wet and on your skin. NIOSH has some information here. hint: Try adding ferrous sulfate to lower the Cr6.

And, if you don’t work in construction, but live in Garfield, NJ, you might have to pull your toenails out to prove you aren’t exposed to hexavalent chromium.

I’m easily impressed with welding and welders. Welding looks so simple, yet hard, dangerous and permanent.

When interviewing your welder, here are some questions to ask:weld1

  • What type of welding are you doing?
  • What type of metal do you weld on? (mild steel, stainless, galvanized)
  • Is there any coating on the metal?
  • What type of flux is used?
  • Where do you weld?, and then, “Where else?”
  • Is there any ventilation in the area you weld?
  • Are there any flammables in the area?
  • Do you wear any PPE when welding? (ear plugs, respirator, leather)
  • When do you use fall protection?
  • Do you have & use welding shields?

What makes welding so difficult is the number of variables involved. The welding variables can change by the minute. Educate your employees on these dangers.

After the above questions, if the employee is agreeable, I ask some additional questions. These are the ones that provoke the best stories:

  • What is the strangest things you’ve welded?
  • Have you ever welding in a really small (confined) area?
  • Have you ever welded with exotic metals? fluxes?
  • What’s the worst thing you’ve welded on?
  • Have you ever gotten sick from welding?

There are many, many more questions to be asked depending on the answers. The authority on this subject, Michael Harris, has written an excellent book on this subject, “Welding Health and Safety“(ISBN 978-1-931504-28-7). It is available from AIHA. It is VERY detailed, and money well spent if you do welding. I have taken his short course (all day) and I learned more than I ever thought possible, and I still can’t even weld!


NIOSHNIOSH has just recommended a new exposure limit (REL) for hexavalent chromium. The new limit is 0.2 ug/m3 as an 8-hour TWA. If you remember, the OSHA PEL is 2.5 ug/m3 (8-hour TWA). SO, if you’re good at math, you can see this is A LOT lower.

The reasoning for this level is they have found a lung cancer risk (get this) EVEN AT 0.2 ug/m3. They recommend bringing airborne levels below this limit for lung exposures.

As I’ve described before, exposures are not limited to just inhalation. Dermal contact is a big concern.

If you have any hexavalent chromium at your facility, or stainless steel (welding, welding2hardfacing, etc.) you need to do more than just air sampling. You need a comprehensive program including wipe samples, medical monitoring, etc. This may not be a specific OSHA rule for your facility.  However, these exposures are something you must manage.


You already knew it. There is a lot to do in industrial hygiene. At times this occupation feels like a safety middleman trying to keep people out of trouble. Occasionally I’m rewarded with really helping someone. In the United States, there is still a lot of occupational hygiene issues and concerns. Overseas, particularly in developing countries, there is even more.

It is hard to obtain accurate exposure data, or illness rates, from these underdeveloped countries. (How does a village of 1,000 people in Kenya report that they’ve had lead exposure to battery recycling?) How these exposures are brought to light is by either a massive death (# of people, quickly) or, someone with a camera able to actually photograph the pollution. As we know, what it looks like doesn’t necessarily correlate with hazardous levels of exposure. But, in some cases, it’s pretty obvious.

I ran across this photo story on pollution (The Guardian, UK). They estimate 125 million people are exposed to industrial pollutants (generic term, I know). This makes occupational related exposures a health risk as big as TB and Malaria! The article is based upon a report from the Blacksmith Institute which included this map of the worst pollution with associated disease.

How does this apply to construction? The worst offenders are lead (Pb) (and other metals), and asbestos.

What can you do? Here’s their recommendation, from the report (p50):

Developing countries need the support of the international community
to design and implement clean up efforts, improve pollution control technologies, and provide educational
trainings to industry workers and the surrounding community

Another NPR article about lead poisoning can be found here.

When performing air monitoring it can be useful to take multiple samples on the same individual throughout the day. Here are some reasons to change out the filters:

  • build up of dust on filter – can cause overloading
  • break-out the exposure data. Morning versus afternoon, or by job tasks, or the physical area the employee is working in, controls vs. no-controls, etc.
  • if you question the employees motives. If you think the employee might skew the results, multiple samples might give you better control- or at least tell you if one is way-out-of-line.

Once you have your data results, how do you combine them?

If you’re taking particulate (dust, lead, cadmium, silica, etc) and you have the concentrations (from the lab) here is what to do.

  1. note the time (in minutes!) and the concentration results (mg/m3, ug/m3, etc) for each sample
  2. multiply the time and concentration for each – then add each number together
  3. finally, divide the above number by the total number of minutes sampled. This is your time weighted average (TWA).

Simple?! Yes. …And it’s really easy to make a mistake too. Check your math, and then eyeball the results and see if they make sense logically.

Here’s an example:

Andrew took three samples during one shift while Shelley was rivet busting through leaded paint. The first sample (118 minutes) was reported as 6.8 ug/m3 of lead, the second was for 245 minutes and had a concentration of 18 ug/m3. The last sample was taken for 88 minutes and was reported a level of 29 ug/m3. The overall results is 17.2 ug/m3 for the total time sampled. (Side: if you sampled for their entire exposure, and they worked longer hours, you could add those hours (assuming zero exposure) into the final time-in step three)

See the math below:

If you use heavy equipment and need to move dirt, rocks or soil, look closely at the buckets. Many times they will be coated with a material called hardfacing. It is a durable (consumable) welding bead laid out in a pattern. This pattern (from what I am told) helps to extend the life of the bucket. Apparently the cost of putting this product on the buckets is well below the cost of replacing the bucket (or teeth, or whatever).

The hazard is really on during the application of hardfacing. See my earlier post here. Hardfacing contains stainless steel (approximately 25%?, but it varies). Heating the stainless steel releases chromium in it’s hexavalent form (Cr6).

If your buckets have this on their exterior, your employees are probably exposed to hexavalent chromium at some point in the year.

However, the pattern is an art & science. Look closely at the side of this bucket…I think I know where this welder got his inspiration.



If you hardface on construction equipment (or anything) you *probably* have overexposure to airborne hexavalent chromium. There are always exceptions, but if you are using a hardfacing wire/stick with any amount of chromium in it, the process (heat) generates hexavalent chromium. For how this happens, go here.

In construction it is quite common to have buckets and equipment with hardfacing applied to the surfaces in order to protect the equipment from excess wear and deterioration. The grid pattern varies, but it can look like this.


I realize that the application of the hardfacing procedure doesn’t occur very often. However, when it does, there is usually high levels airborne hexavalent chromium generated. So, what to do?

  • Use some type of ventilation system (I know, I know, it messes with the shield gas, but do something!)
  • Wear (at least) a 1/2 face tight fitting respirator with P100 (HEPA) filters (honestly, I’d buy a powered air purifying welding hood if I was doing it..and money was not an object)
  • Cover any exposed skin (it can be absorbed by your skin)
  • Designate the area as hazardous and limit the activities in this area (no eating!)
  • Perform air monitoring to verify airborne levels are below limits (and get an IH out to evaluate it)

These suggestions really only scratch the surface of what you should do. Doing all of the above will not even meet the OSHA rules…but it will help protect you from exposure. Here is the OSHA Fact Sheet.  Another article from Welding Design & Fabrication.

An agricultural sprinkler and pipe fitting company would not be first on my list for hexavalent chromium exposures. However, they hired a great manager who happens to keep up on safety concerns. He identified the hazard before any work had started.

This company makes custom fittings and pipe for municipals and agricultural systems. The most durable pipes are made of stainless steel. An employee was performing TIG welding for elbows and joints for a new system. In the past I have found that TIG welding produces the least amount of airborne hexavalent chromium (Cr6), so I was not too worried about the airborne levels that might be measured. (keep in mind that there is still a dermal concern, more info here).

However, after interviewing the employee for awhile, he said that plasma cutting and stick welding also occur. Unfortunately air monitoring during TIG welding does not compare with plasma cutting or stick (arc) welding. Additional air monitoring during those activities will have to be performed.

Stainless steel welding is a great way to generate hexavalent chromium (Cr6). There is chromium in all types of stainless steel. When heating up stainless steel, chromium goes from chromium 3 to it’s hexavalent state (chromium 6).  Look to my other post for the health effect summary.

At this site, we measured just hexavalent chromium for the two welders and the two helpers on site. It is helpful to take wipe samples around the area to see if the material is migrating. If I am really worried about hygiene, I’ll take samples in the shop bathroom or in people’s truck (steering wheels, floor boards).

In general TIG welding does not generate a lot of hexavalent chromium. I’m sure there’s a good reason for this, but I have not heard exactly why. Probably the lower heat, not as much metal used, etc. However, as in all welding, it depends.  One welder was working inside a three foot diameter duct, which is entirely different than welding in an open shop.

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