How Do We Define "Hazardous"? It Depends.

Posted on 7/27/2020 by Scott Dunsmore, CIT

Abraham Lincoln. Abe Lincoln. Honest Abe. The Great Emancipator. 

Call him what you will and most people will know you’re talking about the sixteenth President of the United States.

Unfortunately, the meaning of the word “hazardous” is not so universally understood in the EHS and hazmat transportation world. Across various environmental, transportation, and safety standards, agencies like US DOT, EPA, and OSHA use terms like hazardous materials, hazardous waste, hazardous chemicals, and hazardous substances to describe different sets of “stuff” that they regulate.

But despite the different terminology, these “hazardous terms” must all apply to the same stuff, right?

After all, what is hazardous in the workplace should also be considered hazardous when it goes down the road, or hazardous when it enters the environment.

The regulatory world isn’t that logical or cut and dry.

Different regulatory agencies not only use different terms for the hazardous stuff they regulate (materials, wastes, substances, chemicals, et al.), the definitions of those terms tend to vary from agency to agency, and even from regulatory program to regulatory program.

What’s more, even when agencies use the same term (e.g., EPA hazardous waste and DOT hazardous waste), they are not necessarily talking about the same stuff. It’s enough to drive a sane person crazy.

There are four core programs that have “hazardous” stuff definitions:
  • DOT’s hazardous materials transportation regulations
  • EPA’s hazardous waste management regulations
  • EPA’s hazardous substance release reporting regulations
  • OSHA’s hazard communication regulations for hazardous chemicals
Each term above is defined differently. This is not because the agencies don’t agree on a single definition. Rather, each program’s hazardous item definition is based on the specific objectives and mandates in the rule’s authorizing law.

DOT Hazardous Materials

DOT hazmat shipping labelsThe DOT’s Hazardous Materials Regulations (HMR) were created to protect the public and property from hazards that are likely to occur in transportation. Since transportation is a relatively short period of time, the criteria that the DOT uses focus on acute hazards.

The DOT uses nine numbered hazard classes to organize their definition. The first eight classes are all based on various chemical, physical, toxicological, and radiological hazards (e.g., explosives, flammables, poisons, oxidizers, and radioactives).

Some classes are divided into various divisions that further break down a regulated hazard category.
The ninth hazard class, Miscellaneous Hazards, applies to any material that does not meet any of the standard

DOT hazard criteria, but meets one of six conditions (i.e.., hazardous wastes, hazardous substances, marine pollutants, elevated temperature materials, airplane hazards, and specifically-designated).

For training to master the complex US DOT (and international) hazmat shipping regulations, find a course at now.  

EPA Hazardous Wastes

EPA hazardous waste drumsThe EPA’s hazardous waste regulations were created to protect human health and the environment from the hazards associate with the short- and long-term management of wastes. The EPA uses a combination of specifically listed wastes and characteristics to define those wastes that must be managed under the strict cradle-to-grave management standards.

There are three lists, two process waste lists and one unused discarded commercial chemical products list, of hazardous waste included in the definition. Each list describes different waste that the Agency believes meet the statutory definition of hazardous waste. Since they are descriptions, there is no testing required. A generator simply compares their waste to the various descriptions.

There are four characteristics (i.e., ignitability, corrosivity, reactivity, and toxicity) included in the definition of hazardous waste. The characteristics are based on various chemical and physical hazards. Some of the characteristics have test methods. Others are descriptive, requiring the generator to have specific knowledge of the properties of their waste.

At, find courses to properly manage your site’s hazardous waste from cradle to grave.

EPA Hazardous Substances

The EPA’s hazardous substance release reporting regulations were created under the “Superfund” law (i.e., Comprehensive Environmental Response Compensation and Liability Act). Under Superfund, a hazardous substance is any of the following:
  • Clean Air Act hazardous air pollutants (HAPS)
  • Clean Water Act toxic pollutants
  • Clean Water Act hazardous substance
  • Resource Conservation and Recovery Act hazardous waste
  • Toxic Substances Control Act imminently hazardous chemical substance
EPA hazardous air pollutants or hazardous substancesIn other words, if a material is subject to one of the above regulations, it is automatically a hazardous substance. The EPA then assigns one of five reportable quantities to each substance (i.e., 1, 10, 100, 1,000, or 5,000 lbs.). Any unauthorized/permitted release of a hazardous substance to the environment at or above its assigned reportable quantity requires immediate notification to the National Response Center.
Identify and understand the major EPA air, water, and chemical regulations that apply to your activities with the Complete Environmental Regulations online course.

OSHA Hazardous Chemicals

OSHA’s hazardous communication regulations were created to protect employees from physical and health hazards that they may be exposed to in their workplace. . Since an employee may be working with a chemical repeatedly over a long period of time throughout their career, the definition includes both acute (short-term) and chronic (long-term) criteria.

OSHA GHS hazardous chemical labelOSHA uses 10 health hazard criteria and 16 physical hazard criteria adopted from the international Globally Harmonized System for Classification and Labeling of Hazardous Chemicals (GHS) as well as a few OSHA-specific criteria.

Examples include:
  • Explosives
  • Oxidizers
  • Flammables (gases, liquids, or solids)
  • Corrosive to metals
  • Acute toxicity (oral, dermal, or inhalation)
  • Skin corrosives
  • Eye irritants
  • Reproductive toxins
  • Carcinogens
The Managing Hazard Communication online course will prepare you to implement and oversee a compliant workplace hazard communication program to protect your employees from chemical hazards.

When One Agency Incorporates Another’s Hazard Terms

Some agency’s rules incorporate other agency terms in their regulation. Here’s where it gets tricky and confusing.

The EPA simply states that any waste that either exhibits a characteristic or matches a listed description is a hazardous waste. The DOT, however, says that hazardous wastes are only those Federally-regulated hazardous wastes which are subject to the hazardous waste manifest requirements. So, that means Federal manifest-exempt waste (e.g., universal waste, very small quantity generator waste) would not be DOT hazardous waste.

Equally frustrating is how DOT defines hazardous substances. The DOT says that the materials must not only have a Superfund reportable quantity. It must be at or above its assigned reportable quantity in a single package.

The process of determining which “hazards” are subject to a specific agency’s rules is not a matter of applying common sense. Rather, one must carefully examine that agency’s specific definition and criteria to determine if their specific stuff is a regulated hazard.

If you can keep all of these hazardous terms straight all the time, we tip our top hat to you.  

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