What is crystalline silica?

Stop what you’re doing right now, stand up, and look around the room. Everywhere you look you’ll see crystalline silica.

It’s in the…

– concrete building you’re sitting in.

– the reinforced steel that’s holding it up.

– the computer chips that power your computer.

– the phone in your pocket.

– the fiber-optic cables that are allowing us to communicate.

– the car you drove to work today.

– the road that took you there.

– the window you’re probably looking out of right now, and…

– that favorite coffee cup sitting on your desk.

Why is crystalline silica in so many everyday things? Because there’s so much of it. Just about any mineral you dig up from the earth’s crust  – soil, granite, limestone, chalk, stone, sand, you name it – is going to contain crystalline silica. Crystalline silica is the second most common mineral on the plant.

And as you can see, it’s not bad. In fact, it’s very useful. All the products listed above are made from crystalline silica. And all these products are perfectly safe to use.

The problem with crystalline silica is what happens when we cut, crush, grind or drill it during industrial processes. Industrial processes like concrete truck cleaning.

Concrete truck cleaning

Over time, dried concrete residue builds up inside the rotating drums you see on top of all mixer trucks.  When this happens the truck’s capacity is reduced and it can’t haul as much fresh concrete. The truck also uses more gas because it’s heavier. So, it needs to be cleaned and this is where things get dicey. You see, manual chipping a ready-mix drum stirs up a lot of dust.

A lot of respirable crystalline silica dust.

We’ll get to the problems associated with respirable crystalline silica in a bit. However, right now let’s take a quick look at what a manual chipper does before he begins his job…

Before he gets into the drum the chipper must put on protective clothing and equipment including a…

  • special respirator
  • safety goggles
  • ear protection that has an NRR (Noise Reduction Rating) of at least 30dB
  • clothing that fully covers his skin
  • a hardhat
  • safety boots, and
  • leather gloves

He needs to make sure there aren’t any large pieces of loose concrete inside the drum that could fall on him and that the truck (or the drum) won’t be moved while he’s inside.

Now, let’s find out why respirable crystalline silica is not something you want to mess with.

Ready mix concrete truck

Respirable crystalline silica and silica poisoning

‘Respirable’ is just a fancy word for breathable. If something is ‘respirable’ it means you can breathe it into your lungs. And this is what happens when we crush, grind, drill or cut crystalline silica.

It becomes respirable, or breathable.

These manufacturing processes produce a cloud of silica dust made up of particles 100x smaller than a grain of sand. These particles are so small that we’re able to breathe them deep into our lungs.

This is what makes crystalline silica so dangerous.

If you breathe in respirable crystalline silica on a regular basis over several years there’s a chance you could get sick. Very sick. And there won’t be a cure.

People who work regularly with respirable crystalline silica go on to develop silicosis, chronic obstructive pulmonary disease (COPD), kidney disease, and even lung cancer.

This includes workers who manually clean ready-mix drums because they are exposed to concentrated levels of respirable crystalline silica. In fact, the levels of respirable crystalline silica are so high inside a concrete ready-mix drum that a respirator alone isn’t enough. The truck must be ventilated as well.

Manually chipping a concrete truck’s drum is a dangerous job and that brings us to OSHA’s (Occupational Safety and Health Administration) new rule on silica poisoning.

OSHA’s new rule on silica poisoning

Back in 2016, OSHA decided that the Personal Exposure Limit (PEL) for respirable crystalline silica was set too high. Way too high. So, they dropped it by a whopping 80%. It went from 250 µg/m3 all the way down to 50 µg/m3.

The rule went into effect for the construction industry on June 23, 2017, and employers who don’t follow it risk a substantial fine or even criminal charges if a manual chipper dies from silica poisoning.

So, how does the construction industry meet the new requirement?

They have a couple of options.

They can either follow the control method outlined in Table 1 of OSHA’s new rule or they can decide for themselves how to meet the rule’s new exposure limit of 50 µg/m3. Whichever option they choose they will need to…

  • Develop a written exposure control plan outlining which tasks expose workers to respirable crystalline silica and how they are going to protect them.
  • Identify areas where concentrated levels of respirable crystalline silica are present and how they’re going to restrict access to them.
  • Put a responsible person in charge of this plan.
  • Make sure cleanup methods aren’t exposing workers to respirable crystalline silica. This would include things like using compressed air without ventilation to capture the dust.
  • Offer medical exams to any worker required to wear a respirator for at least 30 days out of the year.
  • Educate employees about the dangers of respirable crystalline silica and how they can limit their exposure.
  • Track their employees’ exposure to respirable crystalline silica and keep a copy of their medical exams on file.

These are tough rules. No doubt. They are much tougher than they were prior to 2017 and employers don’t have a choice about whether to follow them or not.

But, manual concrete truck chipping isn’t the only way to clean the inside of a ready-mix drum. A process called hydro blasting is both quicker and safer.

Hydro blasting: An alternative for cleaning concrete trucks

Manually chipping a ready-mix concrete drum is a slow process that exposes the chipper to the hazards of working in a confined space, noise levels that can permanently damage hearing, and high temperatures (if the drums are cleaned during warm weather).

And, of course, high concentrations of respirable crystalline silica.

Hydroblasting eliminates all that.

With hydro blasting, one person operating a remote control from outside the drum can remove 4000lbs. of dried concrete in about 75 minutes without exposing himself to respirable crystalline silica.

OSHA’s new respirable crystalline silica rule is tough. It’s bad news if you’re in the concrete manufacturing industry. The good news is that manual chipping is no longer the only solution.