Aquatic toxicity assessment of phosphate compounds

Area of Science:

• Environmental Chemistry
• Ecotoxicology

Background:

• Tricalcium phosphate and calcium hydrogenorthophosphate are high-production chemicals with diverse industrial applications.
• Phosphate's role in aquatic ecosystems is debated, with potential for eutrophication but limited data on direct toxicity.

Purpose of the Study:

• To evaluate the toxic potential of phosphate compounds in aquatic environments.
• To assess the acute and chronic toxicity of tricalcium phosphate and calcium hydrogenorthophosphate.

Main Methods:

• Aquatic toxicity tests were performed on fish (Oryzias latipes), Daphnia, and algae (Pseudokirchneriella subcapitata).
• Tests followed Organization for Economic Cooperation and Development (OECD) Test Guidelines under good laboratory practice.
• Physico-chemical properties were sourced from OECD-recommended databases.

Main Results:

• Acute toxicity tests (96-hr LC50) for fish were >100 mg/L for both compounds.
• Daphnia (48-hr EC50) and algae (72-hr EC50) growth inhibition tests also showed no toxicity, with EC50 values >100 mg/L.
• Measured concentrations in tests were significantly lower than the nominal >100 mg/L threshold.

Conclusions:

• Phosphate compounds exhibited no significant toxicity to aquatic organisms at tested concentrations (L(E)C50 > 100 mg/L).
• While direct toxicity is low, excessive phosphate input can still contribute to eutrophication by promoting algal growth.
• Environmental phosphate levels are generally low, suggesting minimal direct toxic risk but continued vigilance on nutrient loading is necessary.