Industrial Hygiene in Construction

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.

Background: We arrived at the welding /fabrication shop where they were working on stainless steel. We were the first to arrive and found this next to the project.

I found 3 things that were blatant “no-no’s”. Want to guess? (see my answers below) You might find more.

1. respirator sitting out -not put away in box (actually sitting next to it!)
2. grinder without a guard
3. eating/drinking in the work area (gum, drinking cup)

In construction there may be a time when employees need to weld on galvanized metal. This poses a unique problem since the zinc oxide fume can cause metal fume fever.  Should employees wear a respirator? Should mechanical ventilation be used? Should they drink milk? before? during and after welding? 

As with my answers to all welding types:  it depends.

However, I will make some generalizations. I have not seen a lot, or high airborne exposures (to zinc oxide) during galvanized steel welding. But, I typically recommend that welders are prepared and ready to wear a respirator if the need occurs. Welding is so variable, it is hard to make generalizations that cover all aspects.

Some questions that I ask before issuing respirators include:

• Does the welder have experience and training with this type of welding?
• How long will the welding occur?
• Is it spot welding? or for a duration of time?
• Is there mechanical ventilation in place, and can it be used for the entire project?
• Is there any portion of the welding that will be in a confined area with limited ventilation?
• Are there any coatings on the metal? Lubricants?

Once a respirator is decided to be issued, I only recommend a 1/2 face tight fitting respirator with HEPA filters. I know that N95 and other types of filtering dust masks do provide protection, but they, in my opinion, are not adequate if you really need them.

And, as far as drinking milk. If you feel sick after welding- drink it. It won’t hurt.

During mild steel welding I very rarely see respirators being worn. I believe this to be “standard practice” (the act of NOT wearing a respirator). However, is this a good idea?

The correct answer is:  It depends.

Explanation:

• I actually think during common mild steel welding, respirators should not usually be required. My experience in air monitoring has demonstrated that most “average” levels are well within occupational exposure levels (OELs).  While sampling under the hood (placing the filterpiece inside the welding hood), the flash hood protects from a lot of exposure. Most of the particulate that is seen-visually is iron.

Caveats:

• “average” welding changes everyday. What is average at one fabrication shop may be totally different from another. Each project may have different welding exposures. Welding inside a 36 inch tube is different than in an open field. You should roughly know what airborne levels you have at your site.
• If the welding contains metals other than what is in typical mild steel (and many times there are other stuff), the air levels can vary. Steel nowadays is so much recycled metal that there is a huge variability in the makeup of new product. Exotics (stainless steel, etc)  and known contaminants (leaded paint, coatings, oils, etc) should be treated very different.
• Long term exposures from metals might be a real health concern. There aren’t many metals in mild steel that you need to inhale.

Finally:

To wear respirators is a good decision. Conditions change and, in construction, this might be every hour. When the project needs to be completed quickly, most welders will not run to the store for a respirator. It is nice to be prepared.

My advice is to issue half-face tight fitting respirators with HEPA (high efficiency particulate air) filters. Train employees WHEN to use them and, if you have safety culture that permits it, trust them to use it when conditions warrant their use.

Most welders wear ear plugs. Why? Because of noise, sure, but also because of slag entering into their ear canal and harming the ear drum.

The average noise levels can vary throughout the day – depending on the project. During the day of this survey, welders were tacking and fabricating stairs and handrails. However, their typical business is large tanks. Do you think the noise levels might vary depending on what they’re making? I do.

I’d also bet that air monitoring during these events would vary. If the welder is inside a large tank performing welding for a few hours, I’d worry about more than just welding fumes. (some might be: welding gases displacing oxygen, electrical hazards, heat exposure, UV, and also the welding metal and rods).

Be safe out there!

Sometimes the perfect storm happens and the situation seems so innocent.  Here are the variables:

• A new shop with a great ventilation system- the airflow moves from Bay 1 to Bay 5 in rapid succession
• Bays 1-4 are mechanics who occasionally work on heavy equipment/ vehicles
• Bay 5 is for welding- has local exhaust and ventilates directly outside

Situation:

• Welder usually does maintenance – small jobs
• On one particular day he is laying down A LOT of wire- and preheats the metal
• Same day- a mechanic needs to clean some parts and uses a cleaner found in most mechanic bays
• Welder “smells” something unusual- get tightness in his chest and almost passes out

What occurred was the perfect combination for a deadly situation. Chlorinated solvents, when their vapors are heated, can form phosgene.

Here is a link to the CDC regarding phosgene. Abbreviated as CG by the military- since it was used in WW1 as a weapon.

As I compiled information for a presentation titled, “Industrial Hygiene in Construction”, I wondered how to approach this topic. What I decided, is that I would start with the most frequent, the most common, with the most room for improvement. So, my list begins.

The caveat is that this list is NOT a list of the relative hazard compared to each other. This is just the IH hazards I see the most frequently. They should really NOT be compared to each other.

1. Silica – in regards to airborne overexposures and lack of controls.
2. Noise – in regards to overexposures and lack of adequate controls.
3. Lead – in regards to compliance with OSHA / EPA.
4. Asbestos – in regards to training employees and compliance with OSHA/EPA
5. Welding – in regards to overexposures and lack of controls.

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.

Some workers were performing MIG (gas metal arc) welding and subarc welding. This is a daily task and their employer requested that we measure the air – as a general assessment tool. In other words, employee’s weren’t concerned, and no one was complaining, but they wanted to explore further into this aspect of their employee’s health and wellness.

We performed air monitoring and analyzed as a welding fume profile which is a number of commonly found welding metals including:

• Antimony
• Beryllium
• Cadmium
• Chromium
• Cobalt
• Copper
• Iron Oxide
• Lead
• Manganese
• Molybdenum
• Nickle
• Vanadium
• Zinc Oxide

Along with the welding fumes, we ran a sample for hexavalent chromium using OSHA Method ID215.

Nowhere in the MSDS (material safety data sheet) did it list “chromium” in the material make-up. However, knowing that it could be a trace metal it might be an issue. MIG welding (in general) isn’t typically of high concern for this hazard. And, as it turns out, the results were found to be below their respective limits.

Employees were not welding the entire day.  At least half of the time was spent fitting, moving, tacking, remeasuring, and gathering materials. Noise was a big issue as well. Most of the day it was quiet, but when the steel would drop, or an “adjustment” to the metal was needed…it was usually followed by a hammer-bang.  Honestly, without the ear plugs, it scared me.