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  • Silica Part I: What Contractors Should Know About the OSHA PEL

Silica Part I: What Contractors Should Know About the OSHA PEL


Published on
January 4, 2022 3:35:44 PM PST January 4, 2022 3:35:44 PM PSTth, January 4, 2022 3:35:44 PM PST

Silica has been a hot topic in the construction industry with the new rule passed by OSHA, which reduced the permissible exposure limit (PEL) to 50 micrograms of respirable crystalline silica per cubic meter of air.  (μg/m3), averaged over an 8-hour day. The previous PEL was 100 μg/m3.

If you’re like most contractors, you’re probably asking yourself, what does that actually mean? Even after reading extensively through the OSHA documentation it can still be confusing.

We’ve been studying silica, exposure and regulation for over 15 years, and frankly it’s still complicated. Because this topic is so important, we created this multi-part series on silica for contractors and industry professionals.

In this first part of the series, we simply break down the factors used to measure the PEL, and why you, as a contractor, should care.

What is PEL?

‘Permissible Exposure Limit’ is the legal limit established by OSHA for worker exposure to silica. In simple terms, how much dust a worker is legally allowed to breath over an eight hour period. The PEL is determined by three factors: Air, Dust and Time. For us to understand the PEL we need to have a better grasp of each factor.


The first factor in calculating the PEL is air. How much air does a person breathe? The answer depends on a number of factors. How big of a person? What is their fitness level? At what activity level are they breathing?

Larger people typically have bigger lungs and breathe more air. Someone who’s physically fit breathes less air than a someone who’s out of shape, and a person running a marathon breathes far more than a person reading a book.

These questions can all be broken down into a relatively simple math problem, but that’s only the first step in calculating the PEL.


The second factor is dust. How much dust is in the air being breathed? Again, that depends.

What type of material is being cut? How big is the brick, paver, or CMU? How long is the cut? How wide is the blade? How much material is being removed in a cut?

The answers to these questions determine how much dust is being released into the air. Even then, there’s still the question of how much respirable crystalline silica is contained within that dust.


The third and final factor used to calculate the PEL is time. Once we know how much air is being breathed, how much dust is contained within that air, and how much of that dust is respirable crystalline silica, we still need to factor the amount of time that air and dust is being breathed.

Throughout this series we break down each of these factors to determine what the PEL actually means to the average contractor.

Why You Should Care

As a contractor, the PEL is important to you and your business. First and foremost is the health and safety of your workers. As an employer it’s critical to understand what risks your employees are being exposed to – and to take appropriate measures to mitigate those risks.

Furthermore, your business is subject to consequences for failing to meet rules and regulations. Whether or not the new OSHA rule is passed, smart and responsible business owners and managers should understand what’s expected of them. Hope is not a strategy, nor is hoping and believing that you’re within the limits without fully understanding what those limits are.

Stay Tuned

In the remainder of this series we’re going to help you understand exactly what the PEL means – after which you can make educated decisions on how to run your business.

On to Silica Part II: The OSHA PEL in Simple Terms

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