In my work and travels, I have the chance to come across such interesting situations and this one stands to cause quite the stir in some food plants. The use of a “special solution” that is made up of Acetic Acid (64-19-7), Hydrogen Peroxide (7722-84-1), and Peracetic Acid (79-21-1) to “treat” poultry for food containment seems to be an “industry practice” these days. My client recognized that Peracetic Acid (79-21-1) is indeed a PSM covered chemical when it’s concentration exceeds 65%; however, EPA’s RMP rule does NOT provide a percentage for Peracetic Acid (79-21-1), thus their “1% Rule” applies to this EHS. In this article, I will use the SDS, 1910.119 Appendix A and Part 68.130 to demonstrate how this “1% Rule” could place a food plant “PAA” use into EPA’s RMP (and possibly OSHA’s PSM – but very unlikely). So let’s start with a review of this “mixture” from the SDS info…
As we can see above, Peracetic Acid (79-21-1) is present in this mixture in a concentration GREATER THAN 1% and for those who may not be all too familiar with PSM/RMP, here is how this HHC/EHS is listed…
OSHA’s PSM…
EPA’s RMP…
NOTE: OSHA has also adopted the 1% Rule, this example would NOT apply since OSHA has an assigned concentration percentage in their listing (e.g. Appendix A).
Step 1
Our Highly Hazardous Chemical (PSM covered chemical) is not over 60% and thus it is NOT a PSM Covered Chemical (e.g. HHC); however…
When an Extremely Hazardous Substance (RMP covered chemical) such as Peracetic Acid (79-21-1) is listed WITHOUT a percentage AND it is present in a solution in a percentage GREATER THAN 1%, the “1% Rule” is applicable. Using the data from the SDS (as shown above), the mixture has between 21-25% Peracetic Acid (79-21-1); so the 1% rule will apply to my mixture.
EPA’s official position on this matter: (emphasis by me)
TOXICS WITHOUT A LISTED CONCENTRATION
For toxics WITHOUT A LISTED CONCENTRATION, if the concentration is LESS THAN one percent you need NOT consider the quantity in your threshold determination. If the concentration in a mixture is ABOVE one percent, you must calculate the weight of the regulated substance in the mixture and use that weight to determine whether a threshold quantity is present.
However, if you can measure or estimate (and document) that the partial pressure of the regulated substance in the mixture is LESS THAN 10 mm Hg, you do not need to consider the mixture. Note that the partial pressure rule does not apply to toluene diisocyanate (2-4, 2-6, or mixed isomers) or oleum.
EPA treats toxic mixtures differently from OSHA. Under the OSHA PSM standard, the entire weight of the mixture is counted toward the threshold quantity; under part 68, ONLY THE WEIGHT OF THE TOXIC SUBSTANCE is counted.
Step 2
I only have to consider the weight of the Peracetic Acid (79-21-1) in the mixture and the RMP TQ is 10,000 pounds.
Peracetic Acid (79-21-1) weighs 9.28 pounds per gallon. (Source: https://www.ams.usda.gov/sites/default/files/media/Peracetic%20Acid%20Technical%20Report%20Handling.pdf)
This means that when I have greater than 40,000 pounds of my mixture I would meet the RMP TQ of 10,000 pounds.
If I had 5,000 gallons of the above mixture, it would look like this:
5,000 gallons X 25% = 1,250 gallons of Peracetic Acid (79-21-1)
Peracetic Acid (79-21-1) weighs 9.28 pounds per gallon: 1,250 gallons X 9.28 = 12,250 pounds which EXCEEDS the 10,000 pound RMP TQ
The MAGIC AMOUNT of this mixture I can have in my “process” is 4,250 gallons as that would put me just under 10,000 pounds.
4,300 gallons X 25% = 1,075 gallons of Peracetic Acid (79-21-1)
Peracetic Acid (79-21-1) weighs 9.28 pounds per gallon: 1,075 gallons X 9.28 = 9,976 pounds
And of course, the “process” can be a bulk tank and all interconnected vessels/piping/tubing/hoses/etc. OR … the use of totes. Some business may be receiving their solution in totes and it sounded as if they were using the 300 gallon totes. This would translate to around 13 of the 300-gallon totes of the mixture all stored within the same area/room would be the MAXIMUM number of totes we could have. If we segregated our totes in such a way that no SINGLE event would involve more than 10,000 pounds of Peracetic Acid (79-21-1) then we could have more of our mixture on site, BUT not in the same “process”.
Step 3
If you can measure or estimate (and document) that the partial pressure of Peracetic Acid (79-21-1) in the mixture is LESS THAN 10 mm Hg, you do not need to consider the mixture. I came across this one a different SDS…
Clean Air Act (CAA) – Accidental Release Prevention
Peracetic acid is listed as a Regulated Toxic Substance at 40 CFR 68.130. Pursuant to the threshold determination provisions for mixtures at 40 CFR 68.155(b)(1), the partial pressure of peracetic acid in VigorOx products (up to 35% solutions) are less than 10 mm Hg at 25°C, and thus the product, as sold, is not subject to the threshold determination under the Risk Management Planning regulations.
So the “partial pressure” is the ONLY exemption REMOVES solutions that are less than 35% Peracetic Acid (79-21-1) for BOTH OSHA’s PSM and EPA’s RMP.