Hazardous Materials Identification, Classification, and Risk Assessment
This domain tests whether you can take an unknown material - a process stream, a discarded solvent, a leaking drum - and assign the correct regulatory and physical hazard labels before anyone stores, ships, or disposes of it. Expect items that combine RCRA characteristic determinations with DOT classification and a basic risk-assessment step.
Two routes to "hazardous waste"
RCRA recognizes listed wastes (F = non-specific source, K = specific industry, P and U = discarded commercial chemical products) and characteristic wastes: D001 ignitable, D002 corrosive, D003 reactive, D004–D043 toxic. One stream can carry several codes. Ignitable liquids have a flash point below 60 °C (140 °F); corrosive aqueous waste has pH ≤ 2 or ≥ 12.5, or corrodes steel faster than 6.35 mm/year; reactive includes water-reactives and wastes that liberate HCN or H2S between pH 2 and 12.5. Toxicity is decided by the TCLP leachate, not total metals - e.g., 5 mg/L lead, 1 mg/L cadmium, 0.2 mg/L mercury.
Risk assessment in four steps
Hazard identification, dose–response, exposure assessment, risk characterization. Risk is a function of hazard times exposure, so a highly toxic material kept in a closed loop can rank below a mild irritant that workers handle open-handed.
Worked example
A spent degreasing solvent is a liquid with a flash point of 48 °C and TCLP lead of 12 mg/L. Flash point below 60 °C gives D001; lead above the 5 mg/L limit gives D008. For DOT, a flash point between 23 °C and 60 °C with an initial boiling point above 35 °C is a Class 3, PG III flammable liquid, so the drum carries a Class 3 label.
Traps
Using total constituent concentration instead of TCLP; applying the pH test to non-aqueous wastes; assuming a listed waste cannot also be characteristic; and assigning a packing group without checking initial boiling point.