Toxicity of Terephthalic Acid (TPA) Smoke Mix to Algae, Daphnia, Fathead Minnows, and Earthworms.

Terephthalic Acid TPA is being considered as a replacement smoke for Hexachloroethane HC. The TPA smoke mix was subjected to toxicity studies to test its effects on Daphnia magna water flea, Selenastrum capricornutum unicellular green algae, Pimephales promelas fathead minnow, and Eisenia foetida earthworm. Toxicity screening was conducted using neat TPA smoke mix in pressed to simulate grenade packaging and loose forms, and as burned residues. The toxicity of neat TPA was less toxic than neat HC burned HC residues were not available. When added to water, the burned TPA residues caused the pH to drop to 4.5, which is not tolerated by the test organisms. However, when the pH was adjusted, the toxicity was greatly reduced. The severity of environmental impact from burned TPA mix will be inversely proportional to the buffering capacity of the ecosystem.