N-(2-nitrophenyl)phosphoric triamide

Endpoint summary

Description of key information

Short-term toxicity to fish:

In a 96-h acute toxicity study according to OECD guideline 203, zebra fish (Danio rerio) were exposed to N- (2 -nitrophenyl) -phosphoric triamide at a nominal concentration of 100 mg/l under static conditions. No effects of N-(2-Nitrophenyl)phosphoric triamide on the mortality of fish were determined. The NOEC (no observed effect concentration) after 96 hours was 100 mg N-(2-Nitrophenyl)phosphoric triamide mg/l.

 Short-term toxicity to aquatic invertebrates:

In a 48-h acute toxicity study according to OECD guideline 202, water fleas (Daphia magna) were exposedunder static conditions to analytically measured test concentrations of 100 mg/LN-(2-Nitrophenyl)phosphoric triamide. No effects of N-(2-Nitrophenyl)phosphoric triamide on immobilisation of daphnids were determined. The NOEC after 48 h was 100 mg/l.

 Toxicity to aquatic algae:

A study was performed to assess the effect of the test material on the growth of the green alga Scenedesmus subspicatus. The method followed that described in the OECD Guidelines for Testing of Chemicals (1984) No 201, "Alga, Growth Inhibition Test". The growth rate in the 100 mg/l treatment as 92% inhibited compared to the control. A NOEC of 6.25 mg/l and a LOEC of 12.5 mg/l have been estimated for the parameters cell growth and growth rate. The EC50 was calculated as 28.3 mg/l (cell growth) and 51.4 mg/l (growth rate).

 Toxicity to microorganism:

The inhibitory effect of N-(2-Nitrophenyl)phosphoric triamide on bacteria was tested by measuring the respiration rate of activated sludge. The study was performed according to the EU guideline No. C. 11. The bacteria of activated sludge from a sewage treatment plant were exposed to the test item at a concentration of 100 mg/1. After a contact time of 3 hours the respiration rate was measured by an oxygen electrode. No inhibition of the respiration activity of the bacteria was measured after the 3 hours contact time. The result demonstrates that the median effective concentration (EC50) is greater than the test concentration of 100 mg/1.

An additional test for inhibition of nitrification was performed as a limit test at the concentration 100 mg/L. The test item is a urease inhibitor. Therefore, for testing whether formation of ammonium from urea in presence of the test item was affected, additional replicates (control, positive-control and test replicates) were tested. In these additional replicates, the nutrient medium was supplemented with 2.15 g/L urea (CH₄N₂O), corresponding to 1 g/L nitrogen from urea (CH₄N₂O-N). The positive control with urea was not necessary for evaluation of the results.In the main study, the test item was tested using six concentrations ranging from 0.01 to 3.2 mg/L test item in nutrient medium supplemented with urea and one concentration containing 100 mg/L in nutrient medium without urea. Urease inhibition was estimated by the content of total inorganic nitrogen (NH₄-N, NO₂-N and NO₃-N) at the end of the test in the test replicates with urea, compared with the control replicate with urea. The duration of the test was four hours. Activated sludge was used as the inoculum. It was taken from a domestic sewage treatment plant and washed before usage. The dry matter was determined as 3.14 g suspended solids/L, giving a concentration of 1.57 g suspended solids/L in the test.

N-Allylthiourea in a concentration of 11.6 mg/L was used as positive control for inhibition of nitrification. At this concentration, complete inhibition of nitrification was reached. The following results were detected for the test item 2-NPT:

Inhibition of nitrification:

4h EC50 > 100 mg/L

Urease inhibition:

4h EC50 = 10 µg/L

 

Long-term toxicity to aquatic invertebrates:

A toxicity test was performed to assess the effects of the test item N-(2-Nitrophenyl) phosphoric triamide on the reproductive output of Daphnia magna during 21 days of exposure. The measured test concentrations of the test item in test solutions ranged from 90 to 110% in fresh samples and from 65 to 117% in aged samples. Based on the above, the results presented are based on the nominal concentrations for the test item as well as on the time-weighted mean concentrations.

The 21 day - NOEC, based on mortality of parents is ≥ 100.0 mg/L test item (equivalent to 102.3 mg/L test item, TW mean). The EC₁₀, EC₂₀ and EC₅₀ values were 2.04, 6.50 and 59.9 mg/L test item (equivalent to 2.04, 6.53 and 60.5 mg/L test item, TW mean) for mean cumulative number of offspring per introduced parent. The EC₁₀, EC₂₀ and EC₅₀ values were 1.97, 6.75 and 70.9 mg/L test item (equivalent to 1.97, 6.78 and 71.7 mg/L test item, TW mean) for mean cumulative number of offspring per survived parent. The first offspring in control replicates was observed at day 10 after test start. No aborted brood or ephippia were observed in any treatment group.

 Long-term toxicity to fish:

An Early-life Stage Toxicity Test (Semi-Static System) of BDP to Zebra-fish was conducted in accordance with OECD test guideline 210 with GLP compliance. The study was conducted under flow-through conditions with the nominal concentration of 1.00, 1.77, 3.16, 5.62 and 10.0 mg test item/L  and control for a period of 35 days after post-hatch. The mortality/survival at embryo, larval and juvenile stages were observed and recorded once a day during exposure. At the end of the exposure, the total dry and wet weight of all surviving fish was determined and the length of surviving fish was measured. Compared with control group, the NOEC for the parameters hatching success, post-hatch success (Survival), number of healthy fish, length of the surviving fish, wet weight of the surviving fish and dry weight of surviving fish was estimated to be greater than 10 mg/L.