Industrial Hygiene in Construction

When measuring by air sampling for a job task, or an employee’s personal exposure, how many samples should you take?

Sometimes it is easier to place one filter cassette (or media) on the employee for the duration of their day.  At the end of the shift, you collect your equipment, mail it to the lab, and they spit out a 8-hour time weighted average (8-hour TWA). This is simple and easy to understand.

However, if you have the time and resources, it is usually beneficial to obtain multiple samples throughout the day. Taking multiple samples allow you to:

• obtain peaks, lows, and anomalies.
• look at: set up & clean up activities (separate from daily tasks)
• measure multiple employees doing the same task (to better capture the job task)
• calculate your own time weighted average
• capture short term exposure levels (STELs), or excursion limits *
• choose appropriate PPE for short duration tasks
• determine if employees are “falsifying” the data (skewing the data high or low)
• reduce filter overloading (in some cases)

There are some reasons NOT to obtain multiple samples:

• collection limit constraints (sometimes the method of sampling does not allow for this type of multiple sampling)
• it can be costly
• it is very time consuming (and nearly impossible, if you have multiple pumps on multiple employees throughout the site)
• difficulty interpreting the data (the math, the inferences, etc)

If you are hiring an industrial hygienist to perform air monitoring, ask about multiple samples. It might be slightly more expensive, but the information and data might be worth the cost.

*ACGIH recommends that if the compound does not have a STEL, all airborne levels should not exceed 3x the 8-hour TWA as an excursion limit.

Yes. If you are in construction, I recommend it. Here’s why:

First, the rules. OSHA does NOT have a specific construction standard for hearing conservation. Why does this matter? Well, the current OSHA rules state that if you have 1 day (that’s only one day) of average noise level above an average of 85 decibels A-weighted (dBA), called the Action Limit, you are required to start a program. Obviously noise levels vary on construction jobsites. I’d guess that most projects have at least one day of levels above 85dBA’s.

And, these particular OSHA rules are terrible. Well, they are terrible if you care about your hearing. (see my earlier post). The rules are simply not protective enough. If you are exposed to noise for 8-hours a day at 90 dBA (the OSHA average exposure limit) you WILL have hearing loss (this is without hearing protection). Does that seem like a very protective rule?  I’ve heard talk about them changing it, but…I doubt it will ever happen.

Second, let’s consider cost vs. reward. To start a hearing conservation program you must measure your employees hearing , called audiometric testing (and do a few other things). It costs approximately $20/employee to do this per year. Compare this with the average claim (of hearing loss) cost of around $20,000. So, if you have 20 employees, and it costs you $400/year…it takes about 50 years to pay yourself back for NOT starting a program. ($20,000/400= 50 years)

Third, consider your employees. Having their hearing checked may seem like a hassle and a worthless exercise, but, some will appreciate it. I’ve found that employees like to know how they are hearing. It’s good if your employer cares how well you hear. It’s also a yearly reminder in hazard awareness to noise.

Because in construction, we know there’s noise!

If you’re dead-set on NOT having a program, you’ll need documented noise dosimetry for each employee, job task, and possible overexposure above 85 dBAs. It is possible  for a construction company to avoid having a program, but you have the burden to prove there isn’t noise. Call your favorite industrial hygienist for help.

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.

Assume your general contractor reports that he has found a material (floor tile, popcorn ceiling, etc) with less than 1%. He wants you to remove it with the rest of the demolition because, as you know, “…if it’s less than 1%, it’s NOT considered asbestos containing!”.

Are you ok to remove it?

Yes, and no. There is more to consider. The “1% rule” (as it’s called) as it is called states that they only regulate asbestos containing materials if they contain more than 1% of asbestos. Here are a few other considerations:

1. OSHA definition. Don’t get stuck on the definition. If you have employees, you must still follow parts of the OSHA rules. At a minimum, you must train your employees, work practices, clean-up and disposal requirments. More details on training here.
2. How were the samples taken? If one bulk sample shows less than 1% asbestos, you still might have a problem. According to the EPA/AHERA sampling rules, some types of materials must have up to 7 samples taken. This rule is in place because, back in the day, asbestos was added to joint compound (or anything similar) and it could really vary in amount according to where you take the sample. In addition, OSHA does not allow for composite sampling (combining the layers).
3. Do you know that 0.99% asbestos is still bad for you? Asbestos is a carcinogen. The greater the exposure, the greater the risk of disease. Any exposure could be the one to cause the disease. If the material is friable and you are disturbing it, I would NOT recommend performing that activity. Hire an abatement contractor.
4. Finally.Let’s assume it’s non-friable, you are not going to disturb it (when removing it) and it’s less than 1%. What will you do if your neighbor next door decides to call OSHA/EPA? Do you have a written plan and procedure? Have your employees been trained on the hazard? How to remove it? How to dispose of it? …Sometimes bad publicity will get you in worse trouble than any monetary fine.

 

After performing an industrial hygiene survey (air monitoring), have you considered when you should resample? Here are some considerations that might help you in determining when.

• Are there specific rules that state when you must resample? For example, the construction lead standard (1926.62) states that you must resample yearly (or actually, that you can only use relevant results for one year).
• Has the process changedsince the last time you sampled? This one is hard to determine. Lot of things can change air monitoring results, here’s a “starter list” of things that can change a process.
  • Different employee?
  • Time of year? Summer versus winter? (closed up/open and humidity)
  • Is a new tool in place?
  • Has the ventilation changed?
  • Have new controls been put in place? (administrative, systems operations)
• Has the product changed? Check the safety data sheet (aka MSDS).
• Are more (or less) employees exposed to this hazard? This might change some assumptions you have made about your risk.?

If you have air sampling performed, make sure you have a written report of your findings. Laboratory results without an explanation of how they sampled, where, # of employees, process description, PPE used, safety data sheets, etc….is worthless. You may remember is well enough, but OSHA will have a hard time believing that it is a similar exposure the next time you do the “exact same thing”.

Having this report and sharing it with the employees will fulfill (part of) the hazard communication standard requirement to employees.

I love the show, “Dirty Jobs” with Mike Rowe. I find it fascinating what people are willing to do for work. Many of the jobs on the show have a true element of danger. Either a pinch point, an animal bite/kick, struck-by, heat/cold extreme, confined space, etc.

Did you ever consider what makes something hazardous?

My “deep thought for today” (thanks Jack Handy) is that education and training can make a job less hazardous. If you know how to do it right, and you know the risk, it doesn’t seem as dangerous anymore. The risk is there, but you know how to handle it, so the “hazard” seems to fade. This week I’ve given two separate asbestos classes to two different employers. At the beginning the employees were genuinely concerned about the hazards. By the end, they looked a lot more comfortable about upcoming project.

Is it any surprise that the HazCom standard is the most OSHA cited rule year over year?

So, keep up the training! Educate the employees on the dangers.

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:

Do you measuring dust on your project/ workplace? If you are a safety professional and you are self-performing this type of sampling here are some tips.

• Measure for the full shift (including prep and clean up) – clean up can be the worst
• Depending on the type of dust, you might need to measure by either respirable, or inhalable (IOM) methodology.  -more on this at a later date
• Watch the dust filter build-up. You might want to change the filter out so as not to overload the cassette. Especially during clean-up.
  
• Have you checked for metals? Many types of dust can contain metals. Ask the laboratory for assistance.
• Consider the placement of the sampling filter. Do you want it downwind? On the collar? Is it on the best employee for sampling?
• Do you perform an area sample? These are not usually recommended, but sometimes they can give you great information.
• Information. Capture all the information that might be important to this sampling. Time, humidity, temperature, controls (or lack of), open doors/windows, employee practices, etc.

As I have said in an earlier post, some OSHA, EPA, and MSHA rules are a good fit. They blend well with health research, scientific technology, good practices, and a low-cost-of-compliance for employers. Other rules are just bad. They are  totally out of date, not protective enough, or just not feasible/practical. Here’s my plug for a good safety manager/industrial hygienist – A good one will know which rules/guidelines to follow.

The New York Times (July 19, 2012, Cara Buckley) recently wrote an article on the US noise standards which are not protective enough for employees. In construction we also have three additional problems.

1. hearing loss is expected (or at least assumed in certain fields – carpenters, sheetmetal, ironworkers, etc.) and,
2. work shifts are usually over 8-hours. Noise exposure is usually calculated on an 8-hour time weighted average. During the busy months, an 8-hour work day is rare. It’s at least 10, maybe 12-14 hours. This doesn’t allow your ears to “rest” between shifts. For more information on extended work shifts go here.
3. extracurricular activities contribute to overall hearing loss – my point is that most construction workers don’t sit at home at the end of their shift. Almost everyone I know in construction is involved in one of these activities: hunting, shooting, motorcycles, water sports, yard work, cars, wood working/cutting, concerts, music, etc. Each of these activities contribute to their overall hearing loss, and again, doesn’t allow your ears to “rest”.

…which reminds me that I need to keep a set of ear plugs in my motorcycle jacket.

Are you measuring for zero accidents? Is this even possible? I agree it is a worthy goal. But, if you are presenting this to management, can you actually achieve it?

There is plenty of discussion around this issue. Maybe a better goal is something harder to measure, but more successful/beneficial in the long term. What about measuring one of these? (or a combination)

• response time from complaint to resolution (from employees)
• number of requests for safety related issues
• satisfaction of safety by workers (rate 1-10)
• safety committee interest & interaction
• decrease in airborne exposure levels year over year
• keeping track of engineering/administrative controls put in place per year

My 2 cents.