The world is full of hazardous and noxious substances. They're used for good purposes, but eventually whatever hasn't been consumed in their use needs to be disposed of. There are approved ways to dispose of toxic substances, but there are inherent risks. The materials may leak out of their containers overtime, contaminating the soil and potentially the groundwater, affecting local residents and the environment itself. Sometimes the materials are spilled in an accident of some sort, or simply abandoned inappropriately by the party in control of the materials. The hazards became apparent in the 1970s when a power company dumped 21,000 tons of hazardous chemicals into the abandoned Love Canal project, then covered it over with dirt and leased out the land. The chemicals had contaminated the groundwater and over time the residents were affected. This and the existence of other contaminated sites led Congress in 1980 to establish the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) which is commonly known as Superfund. The Act allows the EPA to step in and either force the company that caused the spill or accumulation of toxic waste to clean up the site, or for the EPA to clean it up and pay for those costs. The law created a tax on chemical and petroleum industries to create a trust fund that is used for cleaning up toxic sites. It established prohibitions and requirements surrounding closed and abandoned hazardous waste sites, provided for liability for those responsible for the release of waste at those sites and established a trust fund to provide for cleanup when no responsible party could be identified.

Superfund applies not to just immediate spills, but sites where toxic waste may have been dumped in the past and where the containment for such waste is now leaking or otherwise contaminating the ground, risking harm to people and the environment as a whole. Companies go out of business and it's possible that a site may not be identified as a toxic site for many years; in such cases, if no responsible party can be found, liability could be assigned to the existing owner of the site or the trust fund would be used to fund cleanup of the site.

There are four classes of liable parties under Superfund: