Numerous potential sources of these toxicants exist within the basins. The toxic substances include:
- herbicides used in aquatic weed control
- inputs from a variety of petrochemical and chemical industries along the Mississippi River
- light industry and domestic inputs from population centers
- storm and urban runoff
- atmospheric deposition
- recreational and commercial boats/ships
- drilling fluids and produced waters from oil and gas production
- runoff and leachate from hazardous waste sites
- pesticides and herbicides from agriculture.
The greatest inputs of toxic substances into Barataria-Terrebonne are from discharges along the eastern margins of the basins because of heavy industries, large urban centers and agricultural areas along the river corridor.
The factors which determine a pollutant’s risk to people and the ecosystem include toxicity concentration, bioavailability (the extent to which an organism can take up these pollutants), and persistence. Environmental contaminants may be very stable, toxic at low concentrations, and bioavailable. Moreover, several may have carcinogenic effects. These characteristics increase the likelihood of toxic effects in the environment itself, as well as, effects on human health.