Hazard classes for materials in transport
Following the UN Model, the DOT divides regulated hazardous materials into nine classes, some of which are further subdivided. Hazardous materials in transportation must be placarded and have specified packaging and labelling. Some materials must always be placarded, others may only require placarding in certain circumstances.
For example, in Australia, Anhydrous Ammonia UN 1005 is classified as 2.3 (Toxic Gas) with sub risk 8 (Corrosive), whereas in the U.S. it is only classified as 2.2 (Non Flammable Gas).
http://en.wikipedia.org/wiki/Dangerous_goods

A hazardous waste is any substance that poses a danger to human health or the environment, according to the U.S. Environmental Protection Agency (EPA). The EPA categorizes hazardous wastes into eight broad classifications. The EPA includes a ninth category for miscellaneous waste that does not fall into one of the eight categories, yet is still considered hazardous. Asbestos is one example of a miscellaneous hazardous

Class 1: Explosives
• The United State Department of Transportation regulates the transport of this class of hazardous waste. Explosives are broken down into subclasses based on the type of impact the material could potentially cause, as well as its fire hazard.
Class 2: Gases
• Class 2 includes flammable gases such as hydrogen, as well as poisonous gases such as hydrogen cyanide or chlorine gas. These gases are often byproducts of industrial processes.
Read more: Eight Classes of Hazardous Waste | eHow.com http://www.ehow.com/list_6039722_eight-classes-hazardous-was...

Listed hazardous waste are materials specifically listed by regulatory authorities as a hazardous waste which are from non-specific sources, specific sources, or discarded chemical products [2].
http://en.wikipedia.org/wiki/Hazardous_waste
Listed Wastes
Related Links
Waste Listing Determinations, Delisting, and Exclusions
Documents
Hazardous Waste Regulations: User-Friendly Reference Documents
By definition, EPA determined that some specific wastes are hazardous. These wastes are incorporated into lists published by the Agency. These lists are organized into three categories:
1. The F-list (non-specific source wastes). This list identifies wastes from common manufacturing and industrial processes, such as solvents that have been used in cleaning or degreasing operations. Because the processes producing these wastes can occur in different sectors of industry, the F-listed wastes are known as wastes from non-specific sources. Wastes included on the F-list can be found in the regulations at40 CFR §261.31 .
2. The K-list (source-specific wastes). This list includes certain wastes from specific industries, such as petroleum refining or pesticide manufacturing. Certain sludges and wastewaters from treatment and production processes in these industries are examples of source-specific wastes. Wastes included on the K-list can be found in the regulations at 40 CFR §261.32 .
3. The P-list and the U-list (discarded commercial chemical products). These lists include specific commercial chemical products in an unused form. Some pesticides and some pharmaceutical products become hazardous waste when discarded. Wastes included on the P- and U-lists can be found in the regulations at 40 CFR §261.33 .
http://www.epa.gov/osw/hazard/wastetypes/listed.htm