Industrial Hygiene in Construction

Question: During mixing of portland cement bags of material (or similar types), am I overexposed?

Maybe, likely. But, probably not to silica. Most manmade, off the shelf products do not contain free-silica, or respirable fraction of the dangerous parts of silica. However, there is overexposure to respirable and total dust. But, be forewarned, if the product has rocks in the material, these may contain silica and if you cut the cured product- you can release respirable silica.

So, best practice is to:

• Use a product without silica (look for the warning on the SDS/MSDS, or bag)
• Eliminate any visible dust by water control methods (misting) or use local exhaust ventilation
• Don’t be dumb; stay upwind. Or, at least do the mixing away from others
• Wear a respirator
  • N95, aka paper dust maks is ok** (but, I’ve got a strong opinion of these)
  • 1/2 face tight fitting respirator with P100 (HEPA) filter is best

**You really do not know which respirator to wear unless you have performed airborne exposure monitoring**

The latest push from NIOSH is ridiculous, in a bad way. It’s titled, “Recognizing N95 Day” on September 5. I’ve written about these types of respirators before.

Let’s start with:

• NIOSH estimates 20 million workers exposed to airborne health risks
• N95 (s) are the most commonly used respirator
• NIOSH certifies all respirators. And, OSHA requires all respirators to be certified by NIOSH
• All certified respirators must have an “assigned protection factor”, which is a level of protection they are able to achieve
• N95 respirators are certified to provide a protection factor of “up to” 5 times the exposure limit

For the record, I am not disputing how NIOSH certifies respirators, or if these respirators can achieve a protection factor of 5 (5x the exposure limit). I will also add that in the healthcare setting (hospitals) these might have a useful role.

Here’s the problem:

• If you need a respirator, you would NOT choose a N95. They are terrible fitting.
  • To put it another way: if you had to work in an environment which had a dangerous airborne hazard, would you CHOOSE this respirator?
  • Or another way: “There is a chance this N95 respirator might protect you, wear this just in case”. (?)
• If you have fit tested these types, you know they are hard to fit, and at best, mediocre in their protection. At times it is hard to fit test a tight fitting 1/2 face respirator on someone who is clean shaven.
• N95 respirators are handed out (like candy) at construction sites for any task which “may be hazardous”.
• Let’s be honest:
  • these are “comfort” masks. AKA:  peace of mind, not for protection.
  • these are cheap. That is why most employers buy them.
• And, let’s mention:
  • exposure levels can vary (have you measured the worst case scenario?)
  • change out schedule? Do your workers wear the same respirators every day? Do they change them when they start getting hard to breathe?
  • facial hair (no one who is on a jobsite has this, right?)
  • there are knock-off N95 respirators which actually aren’t certified (they’re fake)

In this instance I wish NIOSH would spend money on training people to use the correct type of respirator. Or, how to adequately measure the hazards found at various sites.

As a quick review. If you need to wear a respirator, here are the proper steps.

Controlling most of these types of exposures is really simple. If you know the job- and you know it will generate airborne silica = Pre Task Plan!

I wish Superintendents would enforce their project managers, or project engineers, to make a pre-task plan for every concrete/silica producing task. Then, (please don’t stop yet), review the plan once the project starts!

Below are two examples with different outcomes:

1. Cutting concrete block.

The pretask plan called for a garden hose with attachment(s) to wet the cutting area. Everything was perfect until the water was shut off. But, they improvised and found an electric water pump with bucket and recycled the water. It was a great outcome. What if the power went out? They could have used a Hudson sprayer.

2. Grinding plaster off a brick wall.

They built an enclosure and containment. They had a negative air machine with HEPA filters. They had a vacuum with HEPA filters, tyvek, 1/2 face respirator, eye protection, etc. But, as they worked the vacuum couldn’t keep up with the amount of dust generated by the 7 inch Bosch grinder. It was really dusty. They worked like this for days. No one onsite saw them because they were in containment. Unfortunately  the project is almost over and it could have been better. A simple shroud to the grinder, like this one (no endorcement) might have controlled the dust & silica. Sure, it might have been troublesome to find the exact one, and get a vacuum attachment, and have the extra weight, and ….

So, let’s talk to people about silica, talk about solutions, and then check to see if they’re effective.

You must follow both. (I’ve mentioned this before)

OSHA’s rules are very detailed and apply to any amount of lead in paint (even less than 0.5%) if you are disturbing it. The only time OSHA rules do not apply is:

• if you are working as a sole-proprietor (no employees), or
• if you are in some other country.

EPA’s rules are just a start. They apply to any residential facility where there are kids under the age of 6. OSHA’s rules are much more comprehensive and protective. (in some instances, overkill)

To EPA’s credit, they have done a great job of marketing and letting contractors know they insist on compliance. OSHA, on the other hand, only inspects 2% of businesses/year and does virtually no marketing. The chances of OSHA showing up on any given jobsite, is nearly 0%.

OSHA’s rules are very complete and comprehensive. You WILL need air monitoring, blood monitoring, PPE, change areas, water/sanitation, and training. The worst thing you can do is NOT follow the OSHA rules, find overexposures, and then try to “make up” for it. From my experience this scenario is a bad place to be, and happens all the time.

Living in the NW, stucco is not as prevalent, compared to other areas of the US, as a building material. I finally got the opportunity to perform air monitoring for silica during stucco crack repair. From what the contractor explained, only the top layer of stucco (1/8 inch) is removed. He claimed the top layer is mostly an acrylic. The employee was wearing a 1/2 face tight fitting respirator with P100 (HEPA) cartridges. In addition, engineering controls were used.  The contractor had a grinder with a shroud and vacuum to remove the dust. This would not be considered a worse-case sampling scenario. From conversations with the plasterer-employees onsite, grinding is usually “VERY dusty”.

Sampling performed only for the duration of the grinding (3 hours). Conclusion?: We did not find any detectable levels of silica or respirable dust.

Please don’t use this sampling as the only information on how to proceed for your project. However, here are my observations:

• If acrylic material is the top 1/4 inch, you may not impact silica (or have any airborne).
• Airborne dust was very well controlled by grinder with shroud & vacuum (see pic below).
• Assume you will have dust until you can observe (or prove) otherwise. Wear a respirator.
• Perception is huge. If there is a big dust cloud coming from your grinder—even if there’s no silica… the observers don’t know the difference, and, well,…you know the story.

 

This blog-post is directed to employees….the drywall framers, hangers, tapers, fireproofers & plasteres who sand and finish mud & drywall.

Question: What type of respirator do you wear when you sand?

…answer? Anything I can find.

This question misleading… and is similar to the one where the attorney asks in divorce court, “Do you beat your wife only when you’re drunk, or all the time?”

But, reiterate.  Do you ever NOT wear a respirator when sanding?  Answer: No. We always wear a respirator. It’s dusty.

So if I may ask a leading question (as a bad attorney): What type of respirator would you wear if you were worried about OVERexposure?

Answer: a tight fitting 1/2 face (or full face, for eye protection & fogging control) negative pressure respirator with HEPA cartridges.

I think I’ve made my point. Why would you choose a paper dust mask? The fit is mediocre, they are disposable, you cannot fit test them (very well). Who cares if it’s a N95 or P100. You can feel the dust escaping around your nose. Below are some “average” pictures of people sanding. What will you do?   more info here

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.

The question I commonly hear is:

Do I need to wear a respirator while cutting concrete wet? What, if so, what type?

To simple answer is, yes.

If wet concrete cutting is done correctly, you should not need a respirator. However, what happens is that in the field, many variables occur. ((Engineering Controls)) Sometimes the water will be directed at the top of the blade (for cooling, not for dust control). The water must be directed at the cutting site on the blade in order to control dust.

Another variable is ((Administrative Controls)) clean up. Do the workers clean up the wet slurry? Or, do they wait till it’s dry and then use a leaf blower?  Do they vacuum the slurry? What happens when the job is done and the vacuum is in the shop? Does the employee wet it down, or blow it off?

Also, what happens when your worker is cutting wet and the water stops? Does he continue? What about if he get to a curb? Do they get the Stihl hot saw and cut wet? What if they don’t have water for that saw?

So, technically, if done correctly, a respirator should not be needed. However, if you don’t have the protocols, air monitoring data, and management controls in place to do it correctly, get a respirator.

Which respirator, you ask? Minimum would be a tight fitting negative pressure half face with HEPA filters. If they are knowingly performing concrete cutting dry – then it needs to be a full face respirator.

Leaded sheetrock is what the name says, sheetrock with a lead layer. It is used in hospital x-ray rooms and other health office clinics for containing / controlling the emitted x-rays while the machines are in use.

Plastering / Drywall companies who install this type of drywall need to follow the OSHA Construction Rules for lead work. I have heard of airborne exposures being at the exposure limits (50 ug/m3) during the installation due to the cutting and breaking of the drywall. My own personal monitoring has been below the Action Limit (30 ug/m3), but I have consistently found levels above the detection limit. This information should be taken as a caution to others.

For starters the employer will need to provide:

• half face negative pressure tight fitting respirators with HEPA cartridges
• protective clothing (like Tyvek (R))
• containment (for the dust generated)
• training (in lead and respirators)
• hand washing / changing areas
• HEPA vacuums for clean up
• possibly air monitoring (by a qualified industrial hygienist)
• possibly blood lead testing

The sheetrock should be contained during transport. Installation should be performed in a contained area with employees in respirators who are trained and competent. Clean-up should be done with HEPA vacuums. Air monitoring should be performed to assure that employees were adequately protected during their activities.

Working with this type of material is no excuse to cut corners (no pun intended). Protect your employees, the hospital, the patients, and others.