Tetrakis(hydroxymethyl)phosphonium sulphate(2:1)

Endpoint summary

Description of key information

(For more details please read CSR available in section 13).

Additional information

To assess the aquatic toxicity of the active substance THPS, acute and chronic studies are available and were performed on the THPS in solution. The following results were expressed as mainingredient (100% active substance).

Acute toxicity:

Acute toxicity to fish was studied in semi-static or flow-through systems, with freshwater and seawater, on four fish species. Whatever the test conditions, the 96h-LC50, based on mortality, ranged from 65 mg/L (Pleuronectes platessa, seawater species) to 74 mg/L (Lepomis macrochirus, freshwater species). Therefore, THPS is considered harmful to fish.

Acute toxicity to aquatic invertebrates was studied in freshwater and seawater crustaceans, respectively Daphnia magna and Acartia tonsa / Mysidopsis bahia/ Crangon crangon, and one seawater mollusc (Crassostrea virginica). On the basis of the studies performed according to the OECD guideline 202 on D. magna, THPS is considered to be harmful to freshwater aquatic invertebrates (48h-EC50= 11.3 mg/L). The most sensitive species for acute toxicity is A. tonsa, tested according the ISO standard 14669. The 48h-LC50 is 0.45 mg/L. Therefore, THPS is very toxic to seawater aquatic invertebrates. It can be concluded that THPS is very toxic to aquatic invertebrates.

Toxicity to algae and aquatic plant were studied in freshwater (Selenastrum capricornutum) and seawater (Skeletonema costatum) microalgae and freshwater higher plant species (Lemna minor). Microalgae are the most sensitive to THPS exposure. Toxicity to aquatic plant is usually described by two parameters, based on the growth rate or on the biomass production. The effect concentration based on the growth rate (ErC50) ranged from 0.12 mg/L (72h static exposure, for marine species Skeletonema costatum) to 0.492 mg/L (96h static exposure, for freshwater species Selenastrum capricornutum). Therefore, THPS is very toxic to aquatic plants.

Acute toxicity to aquatic microorganisms was assessed through a respiration inhibition test and a nitrification inhibition test using activated sludge. These studies were performed according the OECD guideline 209 and the ISO standard 9509, respectively. THPS inhibits half of the respiration rate when applied at a concentration of 18 mg/L during 3h, and reduces the nitrification process in the same extent at a concentration of 42 mg/L during a 4h exposure.

Acute toxicity to marine sediment organisms was studied in a crustacean (Corophium volutator) and a mollusc (Abra alba). The 10d-LC50, obtained on C. volutator was 1631 mg/kg sediment dw. Moreover, THPS inhibits the defecation rate of half the control value in five days when the exposure concentration reaches 619 mg/kg sediment dw (A. alba).

In conclusion, based on the overall available acute data, the microalgae are considered as the most sensitive aquatic species in short-term exposure, freshwater and seawater species included, with a 72h-ErC50 value at 0.12 mg/L (on Skeletonema costatum). Therefore, THPS is considered very toxic to aquatic organisms (M factor= 1).

Chronic toxicity:

For the aquatic environment, two chronic studies are available, one embryo-larval study in fish (Pimephales promelas) using a flow through system and one on the crustacean reproduction rate (Daphnia magna) in semi-static conditions. The most sensitive end-points for fish are the mortality rate and the body length of the larvae after the 32-day exposure period, with a NOEC of 0.83 mg/L. A study on D. magna, performed according the OECD guideline 202 Part 2, showed that THPS affects in particular the reproduction rate; indeed the NOEC is based on the effects on this end-point, and is equal to 0.0242 mg/L. In addition, as algae and aquatic plant studies are also considered as chronic data, the lowest NOEC value observed based on growth rate was 0.048 mg/L (freshwater species, Selenastrum capricornutum).

In conclusion, based on the overall available chronic data, the aquatic invertebrates are considered as the most sensitive aquatic species in long-term exposure, with a 21d-NOEC value at 0.0242 mg/L (Daphnia magna). As the active substance is readily biodegradable, THPS is considered toxic to aquatic life with long lasting effects (without M factor).

The table below summarised the aquatic toxicity conclusions:

	Retained acute data	Retained chronic data
Fish	96h-LC50 (Oncorhynchus mykiss) = 71 mg/L	32d-NOEC (Pimephales promelas) = 0.83 mg/L
Aquatic invertebrates	48h-LC50 (Acartia tonsa) = 0.45 mg/L	21d-NOEC (Daphnia magna) = 0.0242 mg/L
Algae and aquatic plant	72h-ErC50 (Skeletonema costatum) = 0.12 mg/L	96h-NOECr (Selenastrum capricornutum) = 0.048 mg/L
Microorganisms	3h-EC50 (activated sludge) = 18 mg/L	3h-NOEC (activated sludge) = 2.4 mg/L
Marine sediment organisms	5d-EC50 (Abra alba) = 619 mg/kg sediment dw	-