Toxic contaminants are chemicals that have the potential to harm living organisms. Whether a contaminant actually induces toxicity depends on several factors including concentration, chemical form, availability, and target biological system.

The presence of toxic contaminants in the environment or even tissues does not necessarily signify toxicity. For example, at low concentrations, copper is a micronutrient essential to the photosynthetic electron transport system yet at higher concentrations is marketed as an effective herbicide. The form of mercury influences its toxicity. Methylated mercury is much more toxic than inorganic mercury (Mitra, 1986). Bio-chemical transformations can change benign chemicals to toxic forms and within food chains toxic chemicals at non-toxic concentrations are bioconcentrated to toxic levels. Furthermore, in association with other chemicals, non-toxic chemicals may become toxic.


  • SWAT Reports. Maine’s Surface Water Ambient Toxics (SWAT) monitoring program was established in 1993 (38 MRSA §420-B) to determine the nature, scope and severity of toxic contamination in the surface waters and fisheries of the State. .
    • Dioxin Monitoring Program. Maine’s Dioxin Monitoring Program was enacted in 1988. The Dioxin Monitoring Program was merged with the Surface Water Ambient Toxics (SWAT) Monitoring Program in 2008. For earlier reports from the Dioxin Monitoring program contact Jim Stahlnecker.