At this point, the OSHA silica rules are forthcoming, what should you be doing to prepare?

  • Read the OSHA Small Entity Guide. Initially it is daunting – 103 pages, but much of it is specific to tasks from Table 1 and the full rules are within it, as well. Plus, they have pictures!
  • Identify tasks which could have silica exposures silica-grinding
  • Train employees, identify your “competent person(s)” – my suggestion is: Superintendents/Project Managers
    • Warn those on your projects: NO VISIBLE DUST on any tasks (cutting, finishing, dry sweeping, etc.)
  • Document activities with airborne silica exposures below 25 ug/m3
  • Identify possible solutions for overexposures
    • Verify airborne levels with personal air sampling
  • Start a process to log the number of days with (any) exposure – >30 is inclusion into medical
  • Find a medical provider that can have medical screen performed & with a B reader

*Thanks Andrew for the photos*


Instead of explaining how to calculate safe levels of chemical mixtures, this will be a reminder.

The American Conference of Governmental Industrial Hygienists (ACGIH) in their Threshold Limit Values (2014), has an excellent explanation of how to calculate a safe level of exposure. However, in summary, if separate chemicals have the same health effects (effect the body in the same way), they may do three things:

  1. Additivity – the sum of their exposure & health effect is A+B. More on this below.
  2. Synergy – the sum of their exposure is MORE than A+B. This is bad, and hard to calculate.
    • Similar in principle to smoking and asbestos. If you smoke and have asbestos exposure, you are worse than just the additive.
  3. Antagonism – the mixed chemicals cancel each other out. It usually never works this way.
    • But, as a terrible example, it would be like acid rain dissolving styrofoam. (I don’t think that’s true, BTW)

Back to Additive (Additivity):additive

If two chemicals (or more) in a mixture have similar health effects (central nervous system, or effect the kidneys, for example), then, until you know otherwise, you should assume they have additive effects. Have your favorite Industrial Hygienist use your air monitoring data to calculate the additive effects using the ACGIH Additive Mixture Formula.

This is useful for combining both full shift air monitoring data, short term, and ceiling exposures. Extreme caution should be used if the chemicals are carcinogenic (as low as reasonably achievable (ALARA) is best here), or if they are complex mixtures (diesel exhaust).

It’s a bit confusing, but worthy of reminding ourselves of chemical mixtures.

It’s sad to say, but many construction companies have not yet started a formal hearing conservation program. Their solution is to purchase the best earplugs, for the lowest cost, and give them away like candy.

As I’ve mentioned before: Sometimes OSHA’s rules are protective (meaning: you will be safe) and other times they are really not on par with the health research. Hearing loss and OSHA’s method of measuring noise are NOT protective to employee health (your hearing). For the best method of measuring noise, look to the recommended guidelines of the ACGIH. In order to get the exact parameters, you must purchase their Guide to Occupational Exposure Values (TLVs) booklet. It hasn’t changed (at least for noise) for a few years, but it is still the most up to date on health for your hearing. Here’s a summary of some differences:

  • Exchange rate (how noise doubles and is averaged over time)
    • OSHA uses 5, ACGIH uses 3 >>which means noise doubles every 5, or 3 dB increase
    • this makes a BIG difference in your accumulated average noise level (TWA).
  • Exposure Limit, or Criterion Level
    • OSHA says 90 dBA, ACGIH says 85 dBA
    • Doesn’t seem too different (-5), but remember noise is logarithmic and it’s measured different by OSHA & the ACGIH

NIOSH also has some guidelines, which are very similar to the ACGIH.NIOSH noise

There are some strong benefits to having a hearing conservation program. Here are some examples and suggestions for bettering your own program.

If you have worked in construction for any period of time, you know how loud it can be, and how much exposure is out there. Don’t assume working in this industry that hearing loss will to happen to you. Do something about it. Here’s a presentation from CDC/NIOSH a few years back on how to start.

NIOSHNIOSH has just recommended a new exposure limit (REL) for hexavalent chromium. The new limit is 0.2 ug/m3 as an 8-hour TWA. If you remember, the OSHA PEL is 2.5 ug/m3 (8-hour TWA). SO, if you’re good at math, you can see this is A LOT lower.

The reasoning for this level is they have found a lung cancer risk (get this) EVEN AT 0.2 ug/m3. They recommend bringing airborne levels below this limit for lung exposures.

As I’ve described before, exposures are not limited to just inhalation. Dermal contact is a big concern.

If you have any hexavalent chromium at your facility, or stainless steel (welding, welding2hardfacing, etc.) you need to do more than just air sampling. You need a comprehensive program including wipe samples, medical monitoring, etc. This may not be a specific OSHA rule for your facility.  However, these exposures are something you must manage.


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

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.

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:

If you are taking multiple samples employees to get an average total time weighted average (TWA), here is how you calculate TWAs.

First take the first concentration (mg/m3 or ug/m3, etc.) and multiply it by the time (in minutes). Do this again for each sample. Add each of these calculated amounts together.

Then, divide by the total minutes sampled.

Or, alternatively, by the total time in the work shift (480 minutes for an 8-hour day). You would only do this if you captured all of their exposure and the rest of the day was (in theory) zero additional exposure.

Look at the number. It should make sense and be logical. If not, look at your math, especially the units for each.

If you like math, here’s the formula: