Industrial Hygiene in Construction

I live in a moderate climate, but we had some 102 degree weather and it reminded me of how important it is to have a heat stress program and educate our workers.

Here are some tips and suggestions for keeping this hazard under control:

• Mandatory rest/water breaks (time between work & break dependent on heat) in shade
• Monitor/measure water consumption (& urine, if extreme)
• Educate employees on symptoms and factors which might contribute (medications, were you drinking last night?= deydration)
• Always work with a partner
• Flexible work schedule (start early, leave when conditions get unbearable)
• Increase ventilation
• Consider the space (attics can be worse than conditions outside)
• Provide easy access to emergency services
• One of the coolest (pun intended) ways is a “smart” vest with a downloadable app – workers wear this safety vest and it will alert people when symptoms/conditions get bad (heart rate, temperature, etc). Developed in Australia by RMIT University in Melbourne.

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**

If you haven’t already heard, it is worth while to mention,OSHA now has jurisdiction over confined spaces in construction (in force on August 3, 2015). Hopefully those working in construction have already realized this hazard and have taken steps to prevent injury.

Here are some of my thoughts:

• **although there are many factors, and we should not compare hazards** OSHA estimates an “injury saving” of 780 serious injuries, and 5 lives spared with the confined space rule.  Compare this with the estimated injury saving from the proposed silica: prevent 1,600 cases of silicosis and save 700 lives.  (and, I do realize these cost employers different amounts of $)
• Oregon OSHA – confined spaces already has a (new) construction confined space standard, which is very much different. It will be interesting to see if this; meets/exceeds/or needs to be changed, to comply with the federal rule.
• Since this rule was dropped without much warning, we will wait to see if anyone calls “foul”. Other than political reasons, it is hard to imagine a reason why construction should be exempt from these rules.
• There are some differences in the construction rule and the general industry:
  • Multi-employer work sites are covered
  • Continuous monitoring – when possible engulfment
  • Upstream early warning- when possible
  • Suspension (not cancellation) of a permit

NIOSH (and with the help from some other groups) released a document this last week titled, “Best Practice Engineering Control Guidelines to Control Worker Exposure to Respirable Crystalline Silica during Asphalt Pavement Milling”. 

The issue: These machines are used to remove asphalt roads. They have a drum with teeth on them that essentially chew up the road and asphalt. A lot of respirable silica is generated (based upon the amount of silica in the rocks). The drums get really hot so water is used to cool it.  However, it does not control the respirable silica dust.  I’ve written (or, maybe complained) about the issue here, in 2010. And, I was informed, some good people were working on it.

The solution: The quick summary is: add more water and ventilation. Not rocket science, right? However, after reading this document, it might be. There’s a lot of information and specifics on what worked, and what didn’t. It was almost too much detail, but I suppose if you have a $200k+ machine, it is worth the time to figure it out. Below are some details:

• Case studies – adding water and increasing the pressure flow decreased airborne dust
• Tracer gas studies for ventilation effectiveness
• Checklists and flow rate controls
• Diagrams for where to direct water

Another benefit was the documentation of other’s work. There are numerous references  (5 pages!) to scientific articles. I did not notice any cost to implement the recommended changes, and I am curious to know what adding the ventilation system might run. Overall the document is good.

Finally, if you hold-on and continue reading to Appendix C, let me know what that all-means.  🙂

This hazard is somewhat difficult to understand. There are number of reasons for the confusion, but the easiest way to explain it is to realize that:

Summary:

Diesel exhaust = Diesel particulate matter (DPM) = lots of different chemicals & particulates

AND: There is not a perfect way to measure the exact exposure.

The Long Story:

The term ‘diesel particulates‘ includes the following (not a comprehensive list):

• elemental carbon (the most reliable method for testing occupational exposure to exhaust, Birch & Cary 1996)
• organic carbon
• carbon monoxide (CO)
• carbon dioxide (CO2)
• hydrocarbons (PAH)
• formaldehyde
• oxides of sulfur & nitrogen

You can quickly see that these are very different substances, and to make it more confusing, you can change the amounts by:

• the fuel (on road/off, low emission fuel, biodiesel)
• the motor type
• the tuning of the motor (& dynamic versus idle), new motor restrictions
• scrubbers, etc.

In addition, there are not any well-established occupational exposure limits specifically for diesel exhaust. However, the International Agency for Research on Cancer has classified “whole diesel engine exhaust” as a carcinogen (cancer causing), so there is reason for concern. Most of the research and rules are in the mining industry, which uses a lot of diesel equipment and the exhaust really has no where to go.

• OSHA = none, but they have a hazard bulletin, and of course, some of the components have exposure limits
• MSHA = 0.4 mg/m3 for total hydrocarbons and 0.3 mg/m3 for elemental carbon
• Canada (CANMET) for respirable combustible dust (66% of respirable dust in mines is from diesel exhaust) = 1.5 mg/m3
• ACGIH = none (for now)
  • 1995 proposed 0.15 mg/m3 (for diesel particulate matter)
  • 1996 proposed lowering it to 0.05 mg/m3 (for diesel particulate matter)
  • 2001 proposed a different limit of 0.02 mg/m3,
    • but for elemental carbon and
    • said it was a suspected carcinogen
  • 2003 withdrew proposed limit- citing not enough scientific information

Bottom line:

• control the exhaust & where it goes (better fuel, better mechanical, scrubbers, ventilation).
• most exposures to diesel are below the (now retracted) ACGIH TLV of 0.02 mg/m3 (or 20 ug/m3) (Seshagiri & Burton, 2003).
• If you have a confined area, unusual concerns, or a particularly stinky situation; measure for multiple parameters (CO, CO2, elemental carbon and maybe NOx, and SOx). Compare these to their respective limits and classify the exposure (describe the conditions)

Do you smell dirty clothes in your indoor building? Do you suspect your heating ventilation and air conditioning system of causing the smells?

It might be what’s called, “Dirty sock syndrome”. Typically found in high humidity locations. A brief video overview can be found here (You Tube 2:03)

Lawrence Berkeley National Laboratory has good information on indoor air quality and how it affects people as they work. They also have some scientific information about how improving the indoor space (by ventilation, temperature, particles, etc) can create a better environment.

AIHA has a “Position Statement on Mold and Dampness in the Built Environment” (March, 2013).  It lays out the reasons to control moisture in a building, and some basic steps for remedy (spoiler: air sampling doesn’t usually help).

Bottom line: Check your coils before replacing your entire system. Replacing these might be cheaper. Or, sometimes they can be cleaned, but it is a strict protocol. One possible solution is here (I do not endorsement, or recommend this particular product/brand. Do your own research).

Unfortunately I have no problem finding an appropriate picture for this blog on Ebay. People are weird. Yuk.

Industrial hygiene (aka occupational hygiene) focuses on occupational-related diseases due to many reasons.

Have you considered, at your home, maybe even as you sleep, you might be exposed to something hazardous? Below are seven possible hazards in your home (related to IH):

1. Radon. It comes from the ground and they say it causes cancer* (*some people question this toxicological data). You must perform a test to know if you have hazardous levels.
2. Formaldehyde. If you have a newer house you have 2 things going against you: 1. your house is tightly built (no air leaks and limited fresh air) and 2. more particle board (recycled wood) was used in construction. Also, many furniture contains multidensity fiber wood (MDF) which off gas formaldehyde. Again test for it to know if you have dangerous levels.
3. Lead. Is your house built prior to 1978? It probably has leaded paint. Any remodeling might distrupt it and you can expose your kids to lead.
4. Isocyantes. (HDI, TDI, MDI, and others) Can cause asthma & respiratory issues. If your house was insulated with spray foam (polyurethane type) it needs to off-gas for awhile before you move right in.
5. Asbestos. Causes cancer when airborne. If your house was built prior to 1980, you might have asbestos in your pipe insulation, popcorn ceiling, etc. Be sure and have it checked prior to remodeling.
6. Mold. Respiratory diseases.
7. Cleaning products. The symptoms can vary depending on the type of chemicals in the product. Use the recommended gloves, eye protection and respirator, if necessary, while cleaning with chemicals.

Do not be overly concerned about any one thing. Simply test and make any necessary adjustments. However, do keep in mind that most health recommendations for substances relate to normal working adults who go home to a non-hazardous place. There can be issues if you are either: not considered in the general population of healthy workers and, you go home to a place that isn’t free of additional hazards.

I’m easily impressed with welding and welders. Welding looks so simple, yet hard, dangerous and permanent.

When interviewing your welder, here are some questions to ask:

• What type of welding are you doing?
• What type of metal do you weld on? (mild steel, stainless, galvanized)
• Is there any coating on the metal?
• What type of flux is used?
• Where do you weld?, and then, “Where else?”
• Is there any ventilation in the area you weld?
• Are there any flammables in the area?
• Do you wear any PPE when welding? (ear plugs, respirator, leather)
• When do you use fall protection?
• Do you have & use welding shields?

What makes welding so difficult is the number of variables involved. The welding variables can change by the minute. Educate your employees on these dangers.

After the above questions, if the employee is agreeable, I ask some additional questions. These are the ones that provoke the best stories:

• What is the strangest things you’ve welded?
• Have you ever welding in a really small (confined) area?
• Have you ever welded with exotic metals? fluxes?
• What’s the worst thing you’ve welded on?
• Have you ever gotten sick from welding?

There are many, many more questions to be asked depending on the answers. The authority on this subject, Michael Harris, has written an excellent book on this subject, “Welding Health and Safety“(ISBN 978-1-931504-28-7). It is available from AIHA. It is VERY detailed, and money well spent if you do welding. I have taken his short course (all day) and I learned more than I ever thought possible, and I still can’t even weld!

If you operate a ready-mix plant and have concrete trucks, you are aware of this process. Once a year (hopefully, only once) a person must climb into the drum of the ready-mix truck and chip off excess concrete. What happen during regular use, is that some concrete hardens, which usually sets-up over and around the blades. Access into the drum is by either the 3×4 hole in the side, or down the chute.

Yes, it is a confined space (def’n: 1. large enough to enter, 2. not designed for occupancy, and 3. limited entry/egress).

Here are a list of the possible hazards:

• silica dust (from chipping concrete)
• noise exposure
• hazardous atmosphere (curing concrete uses up oxygen, which we DO need BTW)
• slipping hazard (drum is round inside)
• heat stress (if you’re trying to do this activity in the summer)
• eye hazard (chipping)
• electrical hazard (if you’re using water & have an electric hammer)
• lock out / tag out (if the truck drives away, or if the barrel starts turning)

There are many resources available (see below). Some things to keep in mind; ventilation (fans, etc) to control the airborne silica dust are usually not effective (too much dust versus exhaust). Water controls are best, but you must limit the amount of water and the direction of the sprayer. I suggest looking at what others have done.

Keep in mind, if you perform this activity you will need (as a company):

• respiratory program (medical, fit test, written plan)
• confined space program (multi gas meter, written program, attendant?)
• lock out /tag out policy or procedures
• training (for each of the above, and for this specific activity)

At this point I know what my contractor-friends are thinking…I will subcontract this out!   ha. If you do, please make sure your sub is doing it right.

Resources:

Georgia Tech – good presentation & guidance

Georgia Tech/OSHA – Safe Work Practices (in Spanish too!)

Teamsters H&S hazards & controls

Illinois DCEO – Consultation on ready mix cleaning

The first question is, “why is this useful?“. Well, generally speaking, it is helpful to know if you are getting bare-minimum airflow, or if you are creating a wind tunnel on your project. Since many construction projects are not able to mobilize until the last minute, it is useful to make some rough guesstimates and calculate the airflow in the room. One squirrel-cage fan isn’t going to ventilate a warehouse, and 5 of them in a manhole will make welding impossible.  so…moving on.

Air changes per hour (ACH) is a function of the room size and the airflow into/out of the room. It is simply the number of times the volume of air is changed out over a one hour time period. One reason this calculation is so attractive to use is because there are recommended exchange rates for different environments. Some of them can be seen in the picture, the rest can be found here.

To calculate you must know:

• A = Volume of room in cubic feet (ft3)
• Q = Air flow of your fan (s) in cubic feet per minute (CFM)

Rather than reinvent the wheel Wiki has a good summary.

Caveat/Disclaimers. There are quite a few…so be careful.

• Mixing. The air never really mixes when you are exchanging air in this manner. It is dilution ventilation. So,
• Never use this method for any hazardous source, and
• Never use this for any carcinogens (asbestos, benzene, etc).
• Airflow into & out of the space is required, and is never ideal. Make sure there is space for the air to actually exchange.
• Make sure your fans work properly and do provide the manufacturers output.