Water, animal tissue, and sediment testing have identified a variety of toxic substances in the basins. Some of the substances are known cancer-causing agents while others affect reproduction. When some animals consume contaminated food, the toxic concentration is magnified. Human consumption of highly contaminated seafood poses health risks. Toxics found throughout the system come from point sources, such as industry, and non-point sources, such as urban runoff.
Numerous potential sources of these toxicants exist within the basins: 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; and 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.
- Emission of toxic material from hazardous waste, recycling and disposal facilities
- Drilling fluids and produced waters
- Illegal dumping of toxic, industrial and commercial wastes
- Agriculture runoff with pesticides and herbicides
- Sewage plants
- Aquatic weed control
- Mississippi River diversions
- Atmospheric deposition
- Accidental spills
- Leachates from hazardous waste in landfills and inactive hazardous waste dumps
- Storm and urban runoff
- Outfalls of industrial effluents containing heavy metals, PCBs and other toxins
- PCBs from leakages of petrochemical pipelines and storage facilities
- Poisoning of wildlife and fish, and the reduction of reproduction
- Decreases in wetland vegetation
- Contamination of oyster beds
- Decreases in submerged aquatic vegetation
- Loss or reduction of commercial and sport fish and wildlife populations
- Contaminations and closure of commercial and recreational fisheries