I was asked to summarize my thoughts on the OSHA proposed silica rule (which is currently pending). I’ve done it before, but since it was for the ASSE’s Industrial Hygiene Practice Specialty, it seemed fitting to post it on this site as well.

Wondering what is happening with the OSHA crystalline silica rule? In aviation terms it’s called a holding pattern. This airplane may-or may not-land. And, it is anyone’s guess.

If you haven’t heard, Federal OSHA is proposing to reduce the airborne silica permissible exposure limit (PEL) to 50 µg/m³. It is difficult to say how much lower this new rule will be, since the current standard relies on a calculated formula to obtain the exposure limit. However, for rounding purposes, let’s just say it’s a 50% reduction in the PEL. This limit is the same at the NIOSH Recommended Limit but still above the ACGIH (2006) Threshold Limit Value of 25 µg/m³.

Over the last year my views on this rule haven’t changed much: It’s a mixed-bag. There are still overexposures to silica. However, will the new rule change behavior?

To show some of the contrast, let me explain. Overexposures to airborne crystalline silica are still occurring. However, silica deaths have continued to decrease over the recent past (without the new rule). But, will the small employers comply? Or just wait to be cited? There is rarely a perfect solution for all situations. I’d like to provide a perspective balance to both sides of the rule.

The obvious benefit to lowering the silica exposure limit will be to protect overexposures to silica. I believe the rule will accomplish this in a number of ways. Any new rule will generate increased awareness for the subject of silica. The new rule will drive OSHA compliance by both lowering the PEL and by compliance with their additional controls. This will drive changes and modification to industries. Innovation will be spurned for controls and the need to comply.  In turn, this will create more discussions on the topic, the solutions, and overall awareness.

The new rule will get closer to the ACGIH TLV and update the health standards. The original rule was from the 1970s. And, OSHA is on the prowl for ways to update their current PELs.

Health and safety consultants will have an occasion for additional revenue in training, air monitoring, recommending controls, and other opportunities.

The new rule allows for alternatives to sampling. Rather than air sampling, you can choose to “over protect” and assure employees are controlling silica exposures.  This is a great solution for short duration tasks where exposure monitoring is prohibitive (see Table 1 from OSHA’s Fact Sheet). They emphasize control measures for silica.

There are very few new products and control measures for mitigating silica exposure in industry. Technology has somewhat sidestepped innovating products for dust capture and control for concrete work. Hopefully new products will be created to control silica. If nothing else, maybe we will see frequent job safety analysis (JSA, JHA) as a common practice to control exposures.


However, there are notable weaknesses to the proposed rule. The obvious downside is employers are expected to spend money. This will be an additional cost to doing business. Money will be spent on citations, controls for silica, labor during the activities, and for consultants to verify exposures are below the PEL.

This new rule will also allow OSHA to issue citations easier.  There are many items in the new rule which are beyond merely lowering the exposure limit. I imagine compliance officers will cite for failure to implement controls, or other technical aspects, rather than measuring the airborne dust and finding overexposure. Look for more drive-by citations.

And, there will be more confusion. Remember explaining to people how to calculate the current PEL? Well, in the short term, it won’t get easier. Although the PEL will be a fixed amount, there will be other things to explain. And, remember all the OSHA rules for leaded paint? The new rule is similar in how it allows you to provide adequate PPE and controls for “interim” work without measuring airborne levels.  Imagine you are a smaller contractor employer. This will be confusing and a lot of background work in order to use a jackhammer for one small project.

And, analytically, the airborne levels attempting to be achieved are so low, they are at the laboratory detection limits. With laboratory I currently use, to reach the detectable minimum PEL you will need to sample for at least 80 minutes (200 Liters). There is some newer sampling equipment which makes these levels easier to achieve. But, guess what? That will cost more money.  In addition, contained in the rule are mention of specific medical evaluations and facilities for those with continued overexposures. There are not enough medical facilities to support the number of people who need them.


Overall, I believe the new silica rules will help reduce overexposures to silica. The increase in awareness across the US will bring more attention to the danger. Employers who are doing absolutely nothing to control silica will get caught, punished, and hopefully change their ways. For employers already in compliance, there will be a small, but manageable, learning curve. I also see many contractors using interim controls (Table 1) as a guide to easily protect employees on short tasks with high silica exposures.

To stay ahead of the curve, the AIHA has released (2013) a white paper for guidelines on skills & competencies in silica specific to construction. It is a great outline for training your employees. Another great resource for awareness and silica control measures is As a reminder, pre-task planning is still one of the best methods for health and safety.

 Here’s my sampling outfit.

my silica bag


Confession: I missed the assessment of this hazard the first time.

Awhile back I performed air sampling during aluminum welding. The welders were cordial and let me crawl over their welding equipment, poke around old boxes of wire and metal stock. I did not think there were any “real” hazards. We did find some airborne levels of various metals. From the picture can you tell who did the most welding?

welding mce

After I had performed the sampling and the report was sent, I was asked if I had checked for ozone (O3)? I admitted I hadn’t and asked if it was an issue? Well, apparently it is (or rather, might be).

I went back to the shop, begged for another chance, and performed ozone sampling. It wasn’t difficult, but eating crow was the hardest part.

More information on the subject can be found at: NIOSHUK- HSE. Ozone is formed when the UV radiation hits oxygen. The ACGIH TLV is variable (see table below)ozone acgih, and the OSHA PEL is 0.1 ppm.

Health: Ozone, O3, can cause lots of different respiratory illnesses. These can include a decrease in lung function, aggravation of asthma, throat irritation/cough, chest pain, shortness of breath, inflammation of lungs, and a higher susceptibility to respiratory illnesses. ACGIH classifies it as an A4, or not a suspected carcinogen.

Luckily the results were found to be non-detectable (“IH talk” for none-found). Which only means I didn’t find it, not that it is not there. I sampled for a long time (530 minutes) because they were working 10 hour shifts. But, they only welded for a total of approximately 1.5 hours during that time.

If welders are in a confined area, or a small space with limited ventilation, the results might be significantly different.


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.

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:


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)

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.

If you haven’t heard, Federal OSHA is proposing to reduce the airborne silica permissible exposure limit (PEL) to 50 µg/m³. It is difficult to say how much lower this new rule will be, since the current standard relies on a calculated formula to obtain the exposure limit. However, to make this easier, let’s just say it’s a 50% reduction in the PEL. This limit is the same at the NIOSH Recommended Limit and above the ACGIH Threshold Value of 25 µg/m³. Before I offer my opinion, you can state yours to OSHA here, and I’d recommend you do.


OSHA helps


  • Increase awareness by everyone (any news is good news for silica awareness)
  • Further protect employees from overexposures
  • Update the health standards. The original rule was from the 1970s.
  • New products for the industry will be created to control silica, like this.
  • Pretask planning (JSA, JHA) will become more common
  • Consultant hygienists will get more $ to: train, air monitor, etc.
  • Alternatives to sampling. This is written in the proposed rule.
    • Rather than air sampling, you can choose to “over protect” and assure employees have adequate PPE
    • This is great for short duration tasks where exposure monitoring is prohibitive (see Table 1. below from OSHA’s Fact Sheet)

OSHA lead table 1



  • Employers will spend additional money:
    • on controls for silica
    • on labor during the activities
    • on consultants to verify you’re below the PEL
  • OSHA will cite you easier
    • (my guess) is compliance officers will cite you for failure to implement controls, rather than measuring the airborne dust and finding overexposure
    • driveby citations. Look at some of my “caught on cameraoverexposures. It is easy to see why this will be easy for OSHA to cite.
  • More confusion
    • remember how you felt when you started working with leaded paint? Picture that again.
    • smaller contractors might be confused with the changes
  • I’ve heard: the airborne levels trying to be achieved are so low, they are at the laboratory detection limits. (this is a bit beyond me, honestly, but it has to do with chemistry & analytical methods)

Overall, I think lowering the limit will reduce employee overexposures to silica. The increase in awareness across the US will bring more attention to the danger. Contractor employers who are doing absolutely nothing to control silica will get caught, punished, and hopefully change. For good-contractors out there, this will make it easier to explain to your subcontractors who are a little behind. I can see many contractors using Table 1 as a guide to easily protect employees on short tasks with high silica exposures.

Your thoughts? I’d love to hear them. Here is a NY Times Article perspective.

This type of potential exposure usually doesn’t cross my mind. Luckily, the specifications in the construction project (and the obvious towers nearby), alerted us to the hazard.

If employees are working near areas of potential high electromagnetic (EM) activity, you should do something (see below). High EM potential areas are power lines, cellular towers, TV/Radio broadcast sites, etc. We have all heard the dangers of living under high voltage power lines, and this is essentially the same concern: Non-ionizing radiation.

The FCC has a guidance document OET-65 (radio frequency) which has some recommended limits, called maximum permissible exposures (MPE). These limits vary depending on the frequency range and how close/what type of work you are doing nearby. OSHA (1910.97) has some guidance (based upon an old ANSI standard) and the ACGIH also has recommended limits. New research is ongoing due to the increased use, and the future demand, of cell phones. The clearest guidance is from IEEE (C95 radio frequency). They provide recommendations and a sample plan. But, to summarize:

  • look for the source (s) of the radiation (sometimes it’s not obvious)
  • take measurements (might be difficult, unless you have access to a field intensity meter) Ask the FCC?
  • determine risk potential
  • make a plan
    • develop controls – time & distance are easiest radio tower
    • consider off-hours/ shut down of towers (in extreme cases)
  • train
  • consider:
    • cranes, large pieces of equipment that may resonate with a certain frequency
    • heat from stored energy
    • nondescript symptoms, which is usually the first sign of a problem

This is a somewhat new field (no pun). But, remember when power lines, cell towers, and tv/radio stations were installed. – The goal wasn’t to keep these away from people, it was to bring them closer. How close should we get? I’d love to hear if anyone has been dealing with this a lot in construction.

From what I have seen, there are not a large amount of formaldehyde exposures in construction. However, there is A LOT of formaldehyde used in construction materials. Formaldehyde can be dangerous at levels undetectable by your nose. And, the symptoms of exposure are nondescript (irritant & tingling of eyes, nose, respiratory tract).

Here are some products that may contain trace (or more) amounts of formaldehyde:

  • resins in plywood, MDF, CDX, particle board/fiber board
  • garage doors
  • drywall
  • roofing
  • glues / mastics
  • paint/coatings
  • carpets
  • insulation (spray in and batting)

I believe the reason we do not see high exposures is due to the limited duration of exposure, and the open-aired nature during the construction. Some exceptions are warehouses with large storage areas of particle board/MDF. (I have found exposures in these areas)

The OSHA exposure limit for formaldehyde is 0.75 ppm (action limit of 0.5 ppm, and short term limit of 2 ppm). However, this may not be low enough, based upon other standards (ACGIH says 0.3 ppm, NIOSH 0.1 ppm)

Another major issue with this hazard in construction is once the space is occupied.

  • Once construction is done, the space may be sealed up, heated, and additional curing can occur.
  • This may release more formaldehyde, and also NOT allow as much to escape (by dilution ventilation).
  • Compounding this issue are the type of occupants in the building. Are there children, non-working adults, immunocompromised individuals, sick, or elderly occupying this space? The OSHA standards are NOT protective for these types of people.

I do not forsee this type of sign being posted immediately after new construction.

formaldehydeOn the plus side, someone has discovered that plants may help reduce formaldehyde & VOC levels in homes. Horticulture Science Kwang Jim Kim,


The new global harmonization system (GHS) is officially adopted by OSHA. Each state run program is rolling out their acceptance of the new changes. Where I live, we have until December 2013 to train employees in this new type of hazard communication.

Honestly, I’m NOT too EXCITED about it. But, I’m trying to have a good attitude. Below are some good things which may occur:

  • Raise the level of awareness of hazardous materials & their toxicity
  • Train employees (hopefully, retrain) on how to handle chemicals
  • More training = less citations. (?) OSHA’s top ten citations include #3 – hazard communication. Maybe people will actually do the training?! (my guess is that there will be more citations)
  • Consistent information worldwide.  All UN countries should have the same format. (this might take years)
  • Proprietary information will be more visible on the SDS. In the new rules, manufacturers are required to list the % of their proprietary ingredients.
  • Pictograms! They’re so cool. My favorite is the exploding person.
  • Maybe this is my favorite?!: Manufacturers will have to look again at their products and classify them according to the physical & health criteria. Nowadays with more relevant information from worldwide occupational exposure limits, it might help make employers aware of the hazards.
    • This might help OSHA enforce newer exposure limits (other than the 1978 AGCIH TLVs).

How do you plan on training your employees? If you need help, contact me here.



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.

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