The Environmental Protection Agency is adding 12 hazardous waste sites to the list of most-contaminated places in the United States.
Another eight sites are being considered for the Superfund list.
Investigators found toxins like arsenic, lead and mercury at some sites.
The designation puts the sites in line for major cleanups, either by the government or by companies or people deemed responsible for the contamination.
Waste sites are being added in Alabama, Arkansas, Florida, Illinois, Louisiana, Maine, North Carolina and New Jersey. Texas and Ohio both have two sites being added to the list.
EPA says it could take years for cleanups to begin at sites where the government has to pay for cleanup efforts.