Does every hazardous material fall under the purview of the DOT and/or IATA?
No, only hazardous materials being transported “in commerce” are regulated under DOT and IATA guidelines. If a material is being shipped by highway, rail, or ship, the material will be regulated under DOT regulations. If the material is being shipped via air, it will be regulated under IATA regulations. Because most items shipped via air are also transported via highway (FedEx truck, UPS Truck, etc.), DOT regulations would also apply.