(Beyond Pesticides, July 23, 2007) New research finds several species of freshwater fish have lower temperature tolerances when exposed to the widely used pesticides endosulfan and chlorpyrifos. The discovery reveals another key pesticides issue in the global warming debate.
The study, “The Effects of Three Organic Chemicals on the Upper Thermal Tolerances of Four Freshwater Fishes” (Environmental Toxicology and Chemistry, July 2007), is the work of Ronald Patra of Australia’s Department of Environment and Conservation and colleagues. The study establishes the upper temperature tolerances of both unexposed and exposed silver perch, eastern rainbowfish, western carp gudgeon and rainbow trout. Exposed fish were given sublethal doses of endosulfan, chlorpyrifos or phenol.
The results show exposure to endosulfan cause a decrease of temperature tolerance in silver perch by 2.8 °C, eastern rainbowfish 4.1 °C, western carp gudgeon 3.1 °C, and rainbow trout 4.8 °C. Chlorpyrifos decreases temperature tolerance in silver perch by 3.8 °C, eastern rainbowfish 2.5 °C, western carp gudgeon 4.3 °C, and rainbow trout 5.9 °C. Phenol is not shown to cause a significant decrease in tolerance.
The authors conclude, “The reduction in thermal tolerance of fish in the presence of endosulfan and chlorpyrifos suggest that, not only does temperature influence the sensitivity of fish to a toxic chemical, but chemical exposure also affects the temperature tolerance of fishes.”
The additive stress on species from exposure to pesticides and other toxics in combination with rising global temperatures reiterates that reducing pesticide use in favor of non-toxic alternatives remains an important action that protects and improves environmental and human health.