Hazardous waste can be generated in many ways. However, industry is one of the biggest contributors of hazardous waste. For example, the petroleum industry not only produces a high amount of carbon dioxide into the atmosphere, but also produces a sludge like material that collects at the bottom of the tanks. These tanks are used to store crude oil before the refining process. This sludge has been found to contain traces of lead and chromium (6+). Complex laws under RCRA say that while being stored, the waste cannot be considered hazardous. However, when they clean out the tanks (every 6 months), the byproducts that are formed from the sludge can be formed into fuel, and are then considered to be hazardous waste.

Furthermore, when there is an unfortunate oil spill, the oil is also considered hazardous waste. Subsequently, so are leaks out of natural gas lines, etc. A good example of contamination from natural gas lines can be found in the American Environmental Laboratory in an article named "On – Site Analysis Rapid mercury analysis for the field". This article shows how they determine the concentration of mercury in the soil near the manometers of the pipelines. The manometers leak mercury if not properly maintained.

Chemical companies also contribute a significant amount of hazardous waste. There are many examples of this, of which only a few will be mentioned. One of the hazardous wastes produced by chemical companies is heavy metals. For example, when processing copper, large amounts of what’s called acid plant and scrubber blowdown contain amounts of mercury, cadmium, and arsenic. These are considered as hazardous wastes under subtitle C of the RCRA, and must be disposed of accordingly. This is done by on – site treatment, after which the effluent is allowed to be discharged into a nearby river. Another hazardous waste generated by chemical companies is chlorinated compounds. The best example of this is the production of pesticides. However, many companies use chlorinated compound as solvents. For example, dry cleaning uses perchloroethylene (tetrachloroethylene) as a solvent in the dry cleaning unit. However, if the solvent is recovered, and used over again with no byproducts from the recovery process, it is not considered as hazardous waste under laws of RCRA. However, another company may use monochlorobenzene as a solvent. This solvent could be recovered by a distillation process, and used again. However, the water left by the distillation process contains small traces of monochlorobenzene, and is considered as hazardous waste under the same law.

These are just some examples. There are many more examples, and many laws under RCRA that govern how these wastes are dealt with, and if they are considered to be hazardous wastes.