PEL (Perm Exp Limit)

Only the enforcement of the new silica rule has been delayed until September 23, 2107.  The Federal OSHA silica rule is still being implemented and will take effect on June 23, 2017.

OSHA says in their memorandum they are delaying the enforcement because they hope to develop additional guidance materials and train their compliance officers.

I suspect that many individual state plan OSHA (like Cal-OSHA, etc) may also delay like Federal OSHA, whether or not they announce it.

The new silica rule for construction is a lot of work, retooling, and training. If you haven’t started, there’s no time to lose. I would suggest you start by:

  • Examine the tasks you perform which may have dust exposure (grinding, concrete cutting, milling, etc.)
  • Refer to the Federal OSHA Small Entity Guide and see if you are properly tooled (have the correct equipment to control exposure)
  • If the tasks aren’t listed in Table I – then you have more work to do (look at alternative control methods)
  • Train your employees. Both in general awareness & for the competent person. Consider making your own company training video (like this one). Don’t worry, it doesn’t have to be awesome Hollywood cinematography…but having a training which is specific to your company, tools, and activities is best.

There is a lot more to the rule, but the above steps are the best place to start.

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*


I was recently forwarded an article on a gentleman who won a large sum of money ($8.75 million) for an asbestos related disease. There are many people getting these types of settlements for similar exposures.

However, what is interesting, is the attorneys argued the company knew about asbestos in 1965, but the exposure occurred in the 1970’s. Keep in mind, the asbestos rules at OSHA didn’t come out until the 1970s as well. So, exposure occurred before the regulations were in effect.

So, they knew of the airborne hazard, but continued to exposure workers before there was a rule. Does this sound like any modern day issue?   –hint– silica?!

Nowadays with the public being uber-aware of “potential” airborne hazards (mold?), with information so readily available, with OSHA rules outdated (annotated Z1 tables), and others publishing health standards like ACGIH,….the lesson is: protect your employees.

I don’t think we should be arguing about the OSHA rules. Let’s use available information and science. “More Than Just A Number” (article published by AIHA, May 24, 2016).

asbestos snow

You’ve probably heard the Federal silica proposed-rule has moved in it’s next step towards being a promulgated-rule.

And, you’ve hopefully looked at my prior post about the positives and negatives of the rule. I am usually not in favor of more rules, but as a safety person, my overall opinion is the new rule would be good.

However, there is some opposition (EHS Today Summary Article) from a few industry groups and associations, including ARTBANAM, and the ACC in an article to plastic manufacturers. And just recently a lawsuit was filed to stop the rule. They have some good arguments, of which, I think the best are: THERE ARE ALREADY OVEREXPOSURES at the current PEL, and silica related deaths have been in decline for decades.

The ACGIH and NIOSH have been recommending lower airborne limits for years. If you are a construction firm, hopefully you already have (engineering & administrative) controls and respiratory protection in place. If not, the best time to start was yesterday, and the next best time is tomorrow.

cut off saw


OSHA has recently announced the final time frame for the proposed silica rule. February 1, 2015 is their anticipated rule promulgation. However, we will see if anyone protests this new information, and if the date for final rule “sticks”.

AIHA broke the news (at least to me) and you can see their summary here. If this is the first you’ve heard about this new rule, then it’s time to do some research, and I might recommend starting here. There are quite a few new requirements, including a lower permissible exposure limit (PEL).

dust exposure

NIOSH (and with the help from some other groups) released a document this last week titled, “Best Practice Engineering Control Guidelines to Control Worker Exposure to Respirable Crystalline Silica during Asphalt Pavement Milling”cold milling machine

The issue: These machines are used to remove asphalt roads. They have a drum with teeth on them that essentially chew up the road and asphalt. A lot of respirable silica is generated (based upon the amount of silica in the rocks). The drums get really hot so water is used to cool it.  However, it does not control the respirable silica dust.  I’ve written (or, maybe complained) about the issue here, in 2010. And, I was informed, some good people were working on it.

The solution: The quick summary is: add more water and ventilation. Not rocket science, right? However, after reading this document, it might be. There’s a lot of information and specifics on what worked, and what didn’t. It was almost too much detail, but I suppose if you have a $200k+ machine, it is worth the time to figure it out. Below are some details:

  • Case studies – adding water and increasing the pressure flow decreased airborne dust
  • Tracer gas studies for ventilation effectiveness
  • Checklists and flow rate controls
  • Diagrams for where to direct water

Another benefit was the documentation of other’s work. There are numerous references  (5 pages!) to scientific articles. I did not notice any cost to implement the recommended changes, and I am curious to know what adding the ventilation system might run. Overall the document is good.

Finally, if you hold-on and continue reading to Appendix C, let me know what that all-means.  🙂



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


Sorry for the delay in writing. I have had some personal and professional projects taking a lot of my spare time. I have been preparing to present at a couple local conferences on Industrial Hygiene in Construction. It is a good exercise for me to ponder what I should say to these audiences. Here are some takeaways:


My latest guess (subject to change, by even tomorrow) is the Federal OSHA rule for silica will be enacted.

“Why”, you say? …well:

  • Current administration would love to push it through
  • Yes. It’s still an issue in the construction world. Have you driven by a construction site lately?
  • Federal OSHA is also talking about updating the PELs…and this one (silica) is an easy one
  • When?  No idea.

Falls in Construction:

This one is huge. In a bad way. If you look at what kills the most in construction, it’s falls (inclusive of scaffolding, ladders, fall protection, etc.) They cost a lot too. Not just in the number of people killed, but the claims & recovery cost are high. And, near misses in construction are VERY common. For example, just two weeks ago: An 18 year old roofer apprentice was working on a roof.  He stepped onto a piece of drywall and would have fallen to a concrete slab 25 feet below. Luckily someone had moved a piece of equipment directly under where he fell. He only fell four feet and had no injuries.

Hierarchy of Controls:

Is anyone working with these anymore? Just kidding, sort of. But, we can do a better job in construction of:

  1. Engineering Controls first. Can we eliminate this hazard? Has anyone asked to substitute this product for a safer one?
  2. Administrative Controls second. There are ways and methods which we do things in construction. These are usually passed down from journeyman to apprentice. Overall, this is awesome. For example, we need to rethink why we place the rebar on the ground? Can we use saw horses? Better material handling would save a lot of injuries.
  3. PPE third. And as a last resort.

Personal Protective Equipment:

Oh boy. There is a lot of room for improvement here. The wrong equipment, worn incorrectly, not used enough, and damaged. I don’t have the answer for this, except we should create and encourage the best safety culture possible.  I think this helps construction to take pride in their work, and their (and their friend’s) safety.

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.


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)

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