Industrial Hygiene in Construction

At this point, the OSHA silica rules are forthcoming, what should you be doing to prepare?

• Read the OSHA Small Entity Guide. Initially it is daunting – 103 pages, but much of it is specific to tasks from Table 1 and the full rules are within it, as well. Plus, they have pictures!
• Identify tasks which could have silica exposures 
• Train employees, identify your “competent person(s)” – my suggestion is: Superintendents/Project Managers
  • Warn those on your projects: NO VISIBLE DUST on any tasks (cutting, finishing, dry sweeping, etc.)
• Document activities with airborne silica exposures below 25 ug/m3
• Identify possible solutions for overexposures
  • Verify airborne levels with personal air sampling
• Start a process to log the number of days with (any) exposure – >30 is inclusion into medical
• Find a medical provider that can have medical screen performed & with a B reader

*Thanks Andrew for the photos*

If you are in the United States, you have probably been hearing issues with lead (Pb) exposures. The main focus lately has been in Flint, Michigan and their (new) source of water, which contains high levels of the metal. Wiki here.

So, who is to blame?

The NY Times suggests we should blame HUD for the millions of pounds of lead in paint. However, I’m not so sure we can cast all of the blame on them, the legislators, or manufactures. But, we are going to be dealing with lead exposures in the future.

I do not know the depth and extent to which lead poisoning is occurring throughout the US. I’m not sure anyone really does. But, there are MANY sources of lead exposure. For example: leaded gasoline (tetraethyl lead) was used in the past, aviation fuel (av gas low lead) still is, lead in paint, lead in copper pipe solder, lead in fishing weights, lead in ammo, lead in sheet rock, lead in Chineese toys…I could go on.

Bottom line though, if you (or your kids) have elevated lead levels,…there is a source. So, What To Do? Here’s my takeaways:

• Test you & your kids for their blood lead levels.
  • It is a very established method, but isn’t an exact science. Don’t freak out if they are above “background” levels. Just do what you can.
  • The CDC recently lowered their recommended blood lead threshold to 5 ug/dl of blood.
  • Don’t do chelation therapy, unless the blood lead level is REALLY high. How high? I’m not a doctor.
  • DO eat lots of vegetables and fruit. These have found to lower lead levels the best (but maybe not the fastest).
• Find the source.
  • Keep looking, there might be more than one. School, work, hobbies, nearby businesses, daily activities.
  • Measure: dirt, water, paint, your workplace.
  • Consider how small an amount is dangerous. 5 micrograms in 1 deciliter of blood. 5 micrograms is 5 millionth of a gram. A fruit fly weighs about 200 micrograms. So, cut a fruit fly into 200 pieces, take 5 of them…you get the idea.
• Tell others.
  • Recommend that others investigate for themselves.

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**

I titled this post, “hazards of drywall”, but it encompassing most of the common hazards of plaster, mud, gypsum, wall-hangers, tapers, and acoustic employees.

1. Corrosive drywall.

   I have not dealt with this subject on a personal level. However, AIHA has a new guidance document titled, “Assessment and Remediation of Corrosive Drywall: An AIHA Guidance Document“, which is a clarification of an earlier white paper document from 2000, titled, “Corrosive Drywall“. The danger is from a specific type of drywall which was imported from China. After installation it is known to emit sulfide vapors, which corrode copper (electrical wires), and can give off a sulfur smell (HT to JeffH in Ohio).

2. Asbestos in mud/plaster.

   Be aware, some older buildings (pre 1980s) may have asbestos in the mud compound or plaster (not as common). This will be a concern if you are performing demo on these walls. Info here.

3. Silica (dust) in joint (mud) compound.

   Some types of silica I have found to have silica. This can be an issue when sanding. AND, if you install drywall like me…you do a lot of sanding. More information from an earlier post can be found here. NIOSH has some suggestions too.

4. Leaded sheetrock. If you are installing (or demo) leaded sheetrock, you NEED to protect yourself. Airborne levels of lead can approach the exposure limits, even during installation. More info here.
5. Lead in paint. If you’re tying into existing plaster/drywall and there’s paint, you need to know if there’s lead in it. Sanding on the paint is a good way to be exposed. More info here.
6. Ergonomics. Hanging the wallboard takes a toll on your body after 20 years (or less). Not to mention sanding. Washington OSHA (L&I) has a good demo.
7. Noise. Cutting steel studs, powder actuated tools (there’s lead exposure too, you know).
8. Skin hazards. Cutting, but also dermatitis from prolonged exposure to dust.
9. Eye hazards. Dust, carpentry, etc. Working overhead is an easy way to get falling items in your eyes.
10. Falls. Last on my list, but certainly not the least. Scaffolding, working from ladders, and using stilts, to name a few.

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:

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

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