Safety professionals know better than most that the safety regulations created by agencies like US DOT and OSHA often don’t line up neatly. They may overlap in some areas, but diverge in others.
Today, we’re talking about corrosives
—and specifically, how the Department of Transportation (DOT) defines them in the 49 CFR Hazardous Materials Regulations (HMR) versus how the Occupational Safety and Health Administration (OSHA) defines them under its Hazard Communication Standard (HCS).
When you know how and why your materials are regulated by US DOT and OSHA, you are more prepared to make informed decisions about how to train personnel who encounter these materials and protect them on the job.
How US DOT Regulates Corrosives (Hazardous Materials Regulations)
The DOT lumps all corrosive materials into one single hazard class: Hazard Class 8 Corrosives. There are two main ways to have a Class 8 material:
- Materials that cause full thickness destruction of skin within 4 hours of exposure
- Materials that corrode through steel or aluminum at least 6.25 mm (0.25 in.) a year at a test temperature of 55°C (130°F)
If you do have a Class 8 hazardous material, you will need to further classify the material
by assigning a packing group to it, which tells you the relative severity of the hazard. The hazmat packing groups for corrosives are as follows:
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- Packing Group I (high hazard) = completely destroys skin ≤ 3 minutes of exposure time (within a 60-minute observation period)
- Packing Group II (moderate hazard) = completely destroys skin > 3 minutes but ≤ 60 minutes of exposure time (within a 14-day observation period)
- Packing Group III (low hazard) = completely destroys skin > 60 minutes but ≤ 4 hours of exposure time (within a 14-day observation period)
- Packing Group III (low hazard) = corrodes steel or aluminum at least 0.25 in. per year
How OSHA Regulates Corrosives (Hazard Communication Standard)
OSHA’s HazCom Standard uses the Globally Harmonized System (or GHS) to define hazardous chemicals. Under GHS, OSHA identifies three hazard classes for corrosives:
- Skin corrosion/irritation
- Serious eye damage/irritation
- Corrosive to metals
Under OSHA regulations, a material may be assigned to multiple
classes of corrosivity. These classifications do overlap a bit with the DOT definitions above, but there are few key differences.
For the “skin corrosion/irritation
” hazard class, the big difference for GHS is that it includes irritants.
GHS also does not use packing groups. Instead, it uses hazard categories to indicate relative severity.
For skin corrosives/irritants, these are defined as:
- Category 1 = Causes full thickness destruction of skin within 4 hours of exposure time, (which matches the DOT Corrosive definition)
- Category 2 = Skin irritants
Within Category 1 skin corrosives
, GHS does have subclassifications (which align exactly
with the DOT packing groups from above). They are:
- Category 1A = same criteria as PG I = completely destroys skin ≤ 3 minutes of exposure time (within a 60-minute observation period)
- Category 1B = same criteria as PG II = completely destroys skin > 3 minutes but ≤ 60 minutes of exposure time (within a 14-day observation period)
- Category 1C = same criteria as PG III = completely destroys skin > 60 minutes but ≤ 4 hours of exposure time (within a 14-day observation period)
The “serious eye damage/irritation
” hazard class is something that does not have an equivalent in the DOT regulations (although many things that are corrosive to the eyes would also be a skin corrosive). This hazard class is broken up into two hazard categories:
- Category 1 = causes irreversible effects on the eye
- Category 2 = causes reversible eye irritation
For the “corrosive to metals”
hazard class, the good news is that OSHA's criteria are identical to US DOT's metals PG III criteria (anything that corrodes steel or aluminum at 0.25 in. per year). There is only a single category for things that are corrosive to metal, so everything here would simply be Category 1.
If you would like to see more specific defining criteria, the full definitions can be found as follows:
- DOT Corrosives = 49 CFR 173.136 and 137
- GHS Skin corrosion/irritation = 29 CFR 1910.1200, Appendix A.2
- GHS Serious eye damage/irritation = 29 CFR 1910.1200, Appendix A.3
- GHS Corrosive to metals = 29 CFR 1910.1200, Appendix B.16
Hazmat Safety and OSHA HazCom Training
Use these new Lion.com online courses to prepare workers to safely handle, package, and ship corrosive chemicals in your workplace. The courses are designed to cover both DOT and OSHA safety training requirements and are available for a variety of materials:
HazCom: Flammables and Combustibles
HazCom: Compressed Gases