Industrial Hygiene in Construction

The big industrial hygiene conference (AIHCe) is held in a different city each year. This year was Indy, Indiana. Below is my personal top ten list  of “lessons learned” from last week.

1. IH’s need to do a better job of sharing. We don’t share data, experiences, information, knowledge or our ideas well.
2. CPWR is trying to share. Center for Construction Research & Training.  I’m looking forward to seeing their published independent review of local exhaust ventilation (LEV) units.
3. The minimum exhaust rate for a portable exhaust unit must be 106 cfm (cubic feet per min) to capture particulates (dust, silica) during tuckpointing with a 5 in grinder (but it’s also a good rule of thumb).
4. Asphalt milling machines are still a huge silica problem. Water controls are NOT enough. You need a local exhaust system too. (here’s an earlier post I made on it)
5. GHS Safety Data Sheets – it’s not as complicated as you think. There are some significant changes, but don’t worry, OSHA’s here to help (ha). Seriously, more information will be available soon.
6. Ignite. Have you seen these before? Short, stand up speeches about their ideas/passions. Similar to TED. Some were better than others. But, did I mention they were short?
7. Committees. Be careful when you open your mouth. My idea was so great, they are making me do it.
8.  ANSI A10.49! A health standard for construction. Great idea, but lots of work.
9. Check out Environment for Children. I don’t know much about it, but they have a great mission.  Believe me, in the US, we’re WAY ahead.
10. Presentation. It’s all up to you to make it. I will not cast blame on those who had bad presentations. BUT, it reminds me that I should work on this skill. Even if you have something good to say, if you give a horrible presentation, it’s likely no one will notice. On the other side, if your presentation is good, people will listen, even if you’re talking about nothing!  My favorite of the week: Dr. Mike Morgan (Univ. of Washington) on Chromium VI. He was very factual, not too flashy, and make the point without needless details.

‘Tis the season for silica (here, and here too).

I had four observations about this picture,

1. paper dust masks are totally inadequate for this task, and
2. why isn’t there any engineering controls (water?, vacuum?), and
3. why is the observer standing in the dust plume?, and
4. what does the employees do with their clothes after work?

Please be safe out there.

For employees (carpenter, laborer, iron worker, plumber, electrician) using powder actuated tools, please take caution! There are possible airborne lead exposures during powder actuated tool use.

The best safety practice is to eliminate the hazard. In this case there are two easy alternatives;

1. using lead-free loads, or
2. using a pneumatic type nailer (like this one made by Pneutek, Hilti makes a CO2 type as well)

However, if you are an employee, I realize there are times that you are not given a choice. If this is the case, please consider:

• asking for the MSDS for the primer loads (look for lead styphnate, or similar)
• lead exposure can occur by inhalation and by ingestion (wash!)
• wash & be diligent around eating & what you “take home” to your family
• lead exposure to children is serious (they absorb lead better & it causes more detrimental health effects)
• respirators might be required when using these tools (so wear one!)
• working overhead (nailing into ceiling) might have higher airborne levels than other positions
• bringing up these concerns with your safety professional onsite
• performing air monitoring to determine airborne levels (although for the price of an industrial hygiene consultant, you could own a CO2 actuated tool)
• reading more about it from my earlier post here.
  

I recently heard a very good summary of when (or alternatively when-you-DON’T) need to perform air monitoring when working with lead in construction.

Is there leaded-paint (lead based paint) in your project?

• Then you MUST comply with the OSHA lead in construction rules.

On what occasion do I NOT have to perform air monitoring?

• if you don’t have lead (see the first question)
• if you want to provide the minimum required protection for all of your exposed employees (respirators, blood lead monitoring, etc. etc.)
• if you have historical air monitoring data (from another project) that supports the methods you are using

Otherwise (in summary):

• Take a bulk sample of the paint
• Set up all engineering & administrative controls for controlling dust
• Train your employees
• Perform air monitoring during the FIRST day of actual work
• Continue with all controls through the project
• Notify everyone onsite of results
• Require that all subcontractor do the same process

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.

One of my pet-peeves is reporting industrial hygiene results with absolutely no explanation of what happened (or the conditions) on the day of the survey. The results will never be reproducible, verifiable, or really ever used again. If you are going to perform the exposure assessment, tell us what happened. We all know that an “average day” is rarely ever the average.

Sometimes you are not able to choose the time when you are able to perform air sampling or monitoring. But, that is a very important part of the overall picture of the exposure. When sampling I very frequently hear, “You should have been here yesterday”, or “Today is really slow”, or “Can you come back next week when we are doing XXX activity?”.

Those phrases and employee interviews are almost as critical as the air sampling results. They tell you what you DIDN’T see, or capture in your exposure monitoring.

At a minimum you should tell a story about:

• what engineering controls are in place
• what administrative controls are used
• what are the employees doing
• how often does this occur
• is this a worst-case scenario, or just average day
• what happens during set up and clean up
• what products are they using (MSDS)
• what PPE are they using

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.

No, and maybe yes.

Crystalline silica (the dangerous type) is typically NOT added into precast concrete. On the other hand, Silicon dioxide (also called micro silica, or silica fume) is added for strength, bonding, and compression strength to concrete. It is usually added at the cement factory. This type of silica binds with the portland cement and (from an inhalable particulate standpoint) is not dangerous.

However, danger lies it what ELSE is added to the precast concrete…..ROCKS!

Rocks, dirt and soil contain varying amounts of silica in the Northwest US. And, if these are broken, ground, chipped, hammered, they can become airborne….which allows the crystalline silica to be released and THAT is dangerous.

Always use wet methods when working with precast concrete.

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.