Industrial Hygiene in Construction

As I compiled information for a presentation titled, “Industrial Hygiene in Construction”, I wondered how to approach this topic. What I decided, is that I would start with the most frequent, the most common, with the most room for improvement. So, my list begins.

The caveat is that this list is NOT a list of the relative hazard compared to each other. This is just the IH hazards I see the most frequently. They should really NOT be compared to each other.

1. Silica – in regards to airborne overexposures and lack of controls.
2. Noise – in regards to overexposures and lack of adequate controls.
3. Lead – in regards to compliance with OSHA / EPA.
4. Asbestos – in regards to training employees and compliance with OSHA/EPA
5. Welding – in regards to overexposures and lack of controls.

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.

I was at another rock crushing site this week. This company has a mobile crusher that can crush some nice sized rocks. Which, by the way, is unique, since most crushers that can handle these size rocks take various cones, belts and screens.  Air sampling conditions were definitely not “worst case” due to morning mist and cloudy conditions for almost the entire day. However, any dust that was generated was most likely from the crusher- not gravel trucks, haul trucks, or wind. We did perform airborne silica monitoring and noise dosimetry on the crushing crew.

I did emphasize some easy, but usually overlooked, tips for the crew:

• keep the doors closed! (this reduces dust and noise)
• keep the radio and CB turned down as low as you can
• backup alarms should point to the back (not at the cab)
• wear hearing protection in high noise areas (around generators)

It’s still dry here in the Northwest and the crusher operations have been in full swing. This mobile, 2 cone crusher was just moved to the coast for about a six week project. We performed airborne respirable dust monitoring and noise dosimetry on the crushing crew. We use a 37mm aluminum cyclone to obtain the respirable fraction. If you run the pump at 2.5 Liters per minute you get a balanced sample across each size in the curve -5 um (microns) and smaller. I analyze for respirable dust, crystalline quartz and cristobalite. We’ve never found trydimite in this area.

There was visible dust coming from the crusher. However exposure might be a non-issue since everyone was either in the cabs of their equipment, or in the operator’s booth.  Silica exposure is nothing to take lightly. Here is a MSHA video on the subject titled, “What Does Silica Mean to You“. (windows media)

For MSHA noise dosimetry is done very similar to the OSHA methods. There are only slight difference between the two. MSHA has a nice fact-sheet here.

You can see one of the cones in the picture below (before it was running).

I know, the title is wrong.  It should read:  “How to prevent hearing loss“.

Here’s the problem (IMO).  I think most people know how to prevent hearing loss- and in America we can all afford to buy ear plugs. I have also heard of hearing loss claims that are unfounded and totally unrelated to their current work activity.  Even just a one time loud event can cause permanent hearing loss.

Construction companies hand out ear plugs like candy and say, “wear them when it’s loud”. Then, these same construction workers go home buck-up a cord of wood, ride their motorcycle, shoot their gun, and then after dinner go to a rock concert.

So, to avoid a claim, here is my advice:

1. Measure the noise (by dosimetry) at your job site- and do it annually.
2. Start a “hearing conservation program” or, in the simplest words, have your employees’ hearing checked annually.
3. Educate (train) your employees in hearing conservation
4. Give them choices in hearing protection (different brands of plugs, muffs, etc.).
5. Manage their hearing- (see below)

If you notice a loss in their hearing- do something! To manage possible hearing loss, I suggest these additional steps:

1. Retest their hearing. On a Monday, before work.  (To avoid a possible temporary threshold shift)
2. Have another company test their hearing. (sometimes the equipment is out of calibration)
3. Remind your manager to enforce the employee’s use of ear plugs on the job site.
4. Offer to give them ear plugs to take home.
5. Have an Industrial Hygienist (IH) perform noise monitoring at the job site for the full shift (dosimetry).
6. Retest their hearing again a month or two later.
7. Have an audiologist review their audiogram & your noise sampling data and ask for an opinion.

Some workers were performing MIG (gas metal arc) welding and subarc welding. This is a daily task and their employer requested that we measure the air – as a general assessment tool. In other words, employee’s weren’t concerned, and no one was complaining, but they wanted to explore further into this aspect of their employee’s health and wellness.

We performed air monitoring and analyzed as a welding fume profile which is a number of commonly found welding metals including:

• Antimony
• Beryllium
• Cadmium
• Chromium
• Cobalt
• Copper
• Iron Oxide
• Lead
• Manganese
• Molybdenum
• Nickle
• Vanadium
• Zinc Oxide

Along with the welding fumes, we ran a sample for hexavalent chromium using OSHA Method ID215.

Nowhere in the MSDS (material safety data sheet) did it list “chromium” in the material make-up. However, knowing that it could be a trace metal it might be an issue. MIG welding (in general) isn’t typically of high concern for this hazard. And, as it turns out, the results were found to be below their respective limits.

Employees were not welding the entire day.  At least half of the time was spent fitting, moving, tacking, remeasuring, and gathering materials. Noise was a big issue as well. Most of the day it was quiet, but when the steel would drop, or an “adjustment” to the metal was needed…it was usually followed by a hammer-bang.  Honestly, without the ear plugs, it scared me.

Industrial hygiene at a surface-mine rock crushing operation is primarily 2 major hazards: 1. airborne silica dust and 2. noise. (there are many more safety hazards but I will focus on IH)

Silica– this can vary due to:   the amount of silica in the rock, weather conditions, type of equipment, if water is used, and where the miners work around the crusher. If it’s a dry-day the groundmen’s silica exposure is right at the limits. Operators in enclosed booths, and loader operators are usually within the limits, unless their cab doors are open. And, as a caveat, to all of this information: you HAVE to do your own monitoring. There are just too many variables.

Noise– with only a few exceptions, noise levels (dosimetry)  are usually well above the MSHA Action limit of 85 dBA. Therefore most rock crushing operations need to have a hearing conservation program. – which for most companies is just measuring their employees hearing (audiogram) every year.  I always recommend that these companies have an active program. Rock crushers are LOUD.

MSHA inspectors, in our state, usually come out to each of the surface rock crushing sites 2x/year. I think it is great they get as many “safety” visits as they do, however, I’ve heard many complaints about the inspectors. Most complaints  stemming from silly citations that aren’t a safety issue, just a rule interpretation. But, to defend them, they have a hard job. They have to fly/drive all over the place, deal with miners, irritated owners, and make sure someone doesn’t get killed after they leave.

Mines (not just underground) can hurt people….but most people have seen that show on the news.

Hot saw

A mason was cutting concrete block (cinder block) with a Stihl cut off saw (aka hot saw) Measured sound level readings were found up to 113 dBA (decibels A-weighted).  Although full shift noise dosimetry was not performed, given the intensity of exposure, under OSHA rules he should limit his exposure to 0.33 hours (or 20 minutes).  (see chart below – or 1910.95 (b)(2)table G-16)

The mason was wearing hearing protection (ear muffs). With that exposure, and a noise reduction rating (NRR) of 26 NRR, the employee could have exposure to his ear of up to 100 decibels.  – because, you can only take a portion of the noise reduction rating (half of it, is easiest – making the 26 NRR only worth 13).  Therefore 113 minus 13 is 100 at the ear.

Now, to make you worry more. OSHA’s method for viewing noise exposure is antiquated.  Someday we’ll discuss the ACGIH and their TLVs and how they compute noise exposure.

The point: This guy is making some noise, has exposure, and might do this activity all day.

How many hot saws are there in construction? At least he was using a hose to wet the dust down…more of that later.