Industrial Hygiene in Construction

Background: A new client recently had an OSHA health inspection (industrial hygiene). He received citations stemming from overexposures(they found levels above the PELs) to airborne particulates.

The company wondered what to do next. Here were my suggestions:

• Fix the problem. You will need to comply and assure that your employees aren’t overexposed. Even if the inspection made you upset, use your energy to make the situation right. Focus your energy on removing the hazard, not complaining about how you were treated.
  • Engineer the problem out. Remove the hazard. If not,
  • Change your policies so no one is further overexposed. If you can’t fix it by the this, or the above method, then,
  • Provide personal protective equipment to affected employees.
• Request the full inspection package. – this will include the officer’s field notes, interview questions, observations and sampling methodology.
  • look through these documents carefully
  • keep them for your records
•  Informally appeal the citations.
  • at the appeal show them you have complied/changed
  • ask for a reduction in fines (it never hurts to ask)
  • ask to group the citations together – instead of citation 1 item 1a, 1b, item 2, etc. ask to narrow it down to just one
  • bring any additional information which supports your side and/or the changes you’ve made (including training docs, programs, policies, etc.)
• Resample the areas.
  • make significant changes to these areas. Then,
  • hire an industrial hygienist to perform additional sampling in these areas
  • ask them to document the changes you have made to reduce the exposures
  • review this with your safety committee & those affected

I’ve mentioned this before.

If you’re using these tools in construction please be careful.

Quick summary:

• the powder contains lead (Pb)
• you can be exposed to lead when it is airborne, AND if it gets on your hands & you eat it.
• lead is not healthy for kids
• Wash!

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.

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.