Industrial Hygiene in Construction

You know those lead testing kits from the hardware store?  They seem extremely handy, however, they are a bit misleading.

LEAD CHECK ™ and LEAD ALERT ™ use a chemical (rodizonate-based) to instantly tell you if you have lead in your paint. If you use this kit, and the color changes, you have lead present.

They are quick and easy, but have a few HUGE downsides.

• OSHA has stated in a letter of interpretation (7/2003) that these should not be used for determining if lead isn’t present. In other words, you can’t rely on a test that says, “no lead!”
• These kits only check the “top layer” of paint – not the coat of paint below the one you are testing. You must test each layer.
• These kits will not tell you how much lead you have (what percentage). You knew these kits didn’t do this already, but this is useful information!
• Some chemicals may interfere with these type of kits. If you have chromium in your paint, the kit may say there is no lead present, but in fact, the chromium has interfered with the true results.

The biggest issue is that you need to have objective air monitoring to prove that your airborne levels of lead are not overexposing your employees.  A true bulk test (of paint) gives you great information. It tells you the percentage of lead in the paint. This, and your air sampling data, can be used again for future projects. It will also tell you which colors of paint have the highest lead.  Be safe out there!

I recently heard a very good summary of when (or alternatively when-you-DON’T) need to perform air monitoring when working with lead in construction.

Is there leaded-paint (lead based paint) in your project?

• Then you MUST comply with the OSHA lead in construction rules.

On what occasion do I NOT have to perform air monitoring?

• if you don’t have lead (see the first question)
• if you want to provide the minimum required protection for all of your exposed employees (respirators, blood lead monitoring, etc. etc.)
• if you have historical air monitoring data (from another project) that supports the methods you are using

Otherwise (in summary):

• Take a bulk sample of the paint
• Set up all engineering & administrative controls for controlling dust
• Train your employees
• Perform air monitoring during the FIRST day of actual work
• Continue with all controls through the project
• Notify everyone onsite of results
• Require that all subcontractor do the same process

To calculate the number of air changes per hour (N) you will need:

• area of the space (length, width, height) in cubic feet (ft3)
• fan or ventilation (in cubic feet per minute, or CFM)

The number of air changes per hour is calculated by:

N= (60 min/hour) (CFM of ventilation) / Total Cubic feet

How useful is this? Well, it’s a mixed bag.

On the downside:

• It assumes that the air mixes perfectly (which it never does) and that the fan is running properly and accurately. 

On the plus side:

• It does give you an idea of how fast the air is moving in proportion to the total area. That information can be very useful when comparing spaces, comparing the types of ventilation available, or attempting to control a hazardous atmosphere by dilution ventilation.

But, be warned: dilution ventilation is NOT a recommended control for a “dangerous” hazard. As they say, “dilution is not the solution to pollution”.