The disposal of some pesticides in certain quantities involves Resource Conservation and Recovery Act (RCRA) regulations, which include stringent requirements for storage, transport, and disposal of hazardous waste, and severe penalties for failure to comply with regulations. While all pesticides are hazardous materials, not all are legally classified as RCRA hazardous waste (see link: Pesticide Waste vs Hazardous Waste http://psep.cce.cornell.edu/facts-slides-self/facts/pesthazard.aspx). Also, state regulations may be more stringent than the federal RCRA regulations in identifying pesticides as hazardous wastes. The contacts for both solid and hazardous waste disposal in each state can be found at http://www.epa.gov/epawaste/wyl/stateprograms.htm.
For further information, type in 'RCRA Orientation Manual' in the search box of the following EPA Web site: http://www.epa.gov/epawaste/index.htm. In addition, RCRA Online, http://www.epa.gov/osw/inforesources/online/index.htm, allows you to search for documents on disposal, treatment, and other RCRA-related topics.
Photo credit: Washington Department of Agriculture