Industrial Hygiene in Construction

To simplify OSHA’s rules for lead in construction this is how I explain it:

Do you have lead (lead in paint usually) on the construction project? …Then you must comply with the entire rules.

How do you start? You start by listing the tasks where you will disturb the lead. For example, demolition, hand scraping, torch cutting.

After you’ve identified the tasks, then you can look at the OSHA rules and determine the minimum personal protective equipment (PPE) that will be necessary for your employees to wear while they’re performing each individual task.

Next, train your empoyee’s in lead awareness, which is the dangers, prevention and hazards of lead poisoning.

There is one other important aspect. Measuring your airborne levels of lead. This is done by air monitoring with a battery powered pump (and is typically one role of an industrial hygienist). Airborne lead results will indicate if you are generating a lot of lead into the air, or not. If you’re not, you can sometimes downgrade (bad word) the level of respiratory protection for your employees.

• Caveat: this is not a complete summary of the rules. Please know and understand your local and federal rules entirely! This also does not cover the EPA’s Lead Rules which have specific items that you must do.

When performing spray finishing activities with any product that contains isocyanates (diisocyanates, HDI, MDI, TDI) the minimum respiratory protection to be worn is a powered air supply respirator.

The reasoning is simple: isocyanates DO NOT have good warning properties.

Painters can usually tell when their cartridges are wearing-out, or getting “break through”. However, with isocyanates, the odor threshold is much too high to detect (it can be detected, but only at harmful levels).

In addition, isocyanates have a skin-notation, meaning that if the product gets onto the skin, it can be absorbed. As you can see, this employee was not wearing the proper PPE (personal protective equipment). However, when you’re a consultant, you have temper your comments. We did educate him and also told the general manager of our concerns and the reasoning.

On the plus-side, they had a manometer that was used and the employee knew when to change out the filters.  How this simple meter works is this:  A manometer measures the pressure differential between two different areas. In a paint booth it measures the pressure between each side of the air filters for the air coming into the booth. If the pressure gets too high, then the filters are clogged (or built-up). Notice the arrows on the bottom of the gauge to see when to service the filters. When the manometer (in this case) reads above 0.045 either the fan has to work harder, or the air escapes by the filter (in various ways- more information for another time)

I have done a bunch of respirable silica dust air monitoring during drywall sanding activities. I have found varying results from the data (meaning overexposures & within the exposure limits). I have found silica in the drywall mud (or possibly the drywall itself).  I have also found that most drywall sanders wear a paper dust mask. In recent years I have not found any airborne silica in my samples. However! I have found airborne (total) dust levels higher than five times the exposure limits during sanding. What does this mean?

Well, the issue is that most drywall sanders use paper dust masks, or equivalent N95 or P100. Like this.

NIOSH has rated these masks for a protection factor of 5. Meaning that you are “allowed” to be exposed up to 5 times the exposure limit. IMO there are many things wrong with these masks. For starters, their fit on your face is really a guess. There are no “tried-and-true” methods for assuring these masks fit.*  Second, if you admit that you need to wear a respirator (meaning: you need to protect yourself) why would you choose an inferior product? I could go on…

Therefore, or finally, we come to my recommendations:

• if you’re drywall sanding:  wear a 1/2 face tight fitting respirator with HEPA cartridges. It will protect you (given a proper fit) and based on my findings, you can rest assured you won’t be overexposed.

Besides who wants to look like this at the end of the day?

*Quantitative fit testing is a reliable fit test method, but for these types of masks, I find it to be totally useless in the real-world

Asphalt milling machines are used to remove road asphalt in wide sections. It has been awhile since I’ve had the opportunity to perform air monitoring for silica on these operations. However, my experience in the past tells me that they can produce a lot of respirable silica dust. I snapped this picture while I was driving (I was going slow, but yea- probably not safe) on a road crew working.  I didn’t capture the cloud of dust hitting the sunlight, but it was a beautiful/scary sight.

The drums on the asphalt machines have many sharp teeth. The drum is lowered onto the asphalt surface and basically chews up the asphalt while carrying it to a belt. As you can imagine, the drum gets really hot. Water is kept on board the milling machine to cool the drum.  The theory is that the drum is wet, so the silica issue must be at a minimum.  I have found really high exposures to airborne respirable silica during this process. I believe due to the water NOT being directed at the cutting teeth.

The solution? Unfortunately, I don’t have an easy one. For starters, I’d make sure the water is directed at the point of cutting (which can vary from day to day). Respirator are not really an option. The road crew must communicate with each other and doing this with a respirator is extremely hard. The noise from these operations is also very high and most crews have ear muffs with communication head-sets.

I would love to hear your comments on engineering solutions to this issue. I don’t believe there is much research going into this issue.

Many bridges and elevated highways have leaded paint. Lead and cadmium was (and sometimes still) added to paint for durability. Nowadays other heavy metals are used for durability. This particular bridge was near the coast and had already been repainted sometime in the past. Repainting requires the removal of the existing paint by sandblasting.  Since the bridge was previously  repainted with a non-leaded paint, in theory, there should not be any airborne levels of lead, or cadmium. However, I always find airborne levels of lead. Why?

The possibilities are:

• not all of the leaded paint was removed
• recycled blasting agent has trace amounts of lead
• and possibly there are still levels of lead in the new paint that is supposedly “non-lead”

I always ask the laboratory to analyze my air sample for lead, and cadmium. Lead is usually the main contaminant, but occasionally I find cadmium. I will sometimes also have the lab check for zinc and chromium.  The sandblasters wear hooded powered air supply respirators, coveralls, and ear protection while blasting. Some other time I’ll talk about the noise from that activity (it’s LOUD!) and the fall protection issues they face.

Lead is a hazard in two forms: 1. airborne and 2. ingestion- from the transfer of contaminated hands/clothing to being eaten. Hygiene on a lead project is essential to preventing these exposures. A good safety practice, by which to verify that lead is not being transferred is to obtain wipe samples at random (or not-so-random) locations. Lunchrooms, shower/change areas, and pickup trucks are some of my favorite “random” locations.

The views around the area weren’t bad either…

To summarize,  there is no real quick-fix to this type of industrial hygiene assessment. Depending on what type of spray finishing you are performing- will depend on how to proceed. Here are some things to look during your assessments of these areas:

• air flow across the face of the spray area should be at least 100 feet per minute
• review the MSDS for the products you spray, and the solvents, thinners, and A+B parts-everything.
• check the filters – are there scheduled changes? a manometer in place and used?
• no flammables should be inside the booth area
• watch the flow of work- usually there can be improvements- as well as lessons to learn
• is the employees’ skin protected during spraying? (obviously not in the picture-right)
• where does the waste (left over) spray product go?
• ask employees about concerns and health issues

Typically respirators are worn in the spray finish areas. This list is not complete, but for starter, check:

• what type of respirators are being worn? Are they protective enough?
• what type of cartridges are used? Are they changed regularly?
• are there scheduled change out times for their cartridges? where is that posted?
• where are their respirators stored?