Nitrapyrin

Toxicity to aquatic algae and cyanobacteria

Description of key information

96 hour EC50 (growth rate) = 3.3 mg/L; 96 hour NOEC (growth rate) = 0.36 mg/L; freshwater diatom, (Navicula pelliculosa); OCSPP 850.4500, Softcheck (2013)

96 hour EC50 (growth rate) = 4.2 mg/L; 96 hour NOEC (growth rate) = 1.1 mg/L; freshwater cyanobacteria, (Anabaena flos-aquae); OCSPP 850.4550, Softcheck (2014)

72 hour EC50 (growth rate) = 1.7 mg/L; 72 hour NOEC (growth rate) = 0.66 mg/L; unicellular green alga (Selenastrum capricornutum); OECD 201, EPA OPPTS 850.5400, Thompson (1985)

Key value for chemical safety assessment

EC50 for freshwater algae:

1.7 mg/L

EC10 or NOEC for freshwater algae:

0.36 mg/L

Additional information

Three studies are available to assess the toxicity of the test material to aquatic algae and cyanobacteria. All three studies were conducted under GLP conditions and in accordance with standardised guidelines. All three studies were therefore assigned a reliability score of 1 in line with the criteria of Klimisch (1997).

In a study reported by Softcheck (2013), the effect of the test material on the growth of the freshwater diatom, Navicula pelliculosa, was investigated under GLP conditions and in accordance with the standardised guideline OCSPP 850.4500.

During the study an inoculum of 0.874 mL of Navicula pelliculosa cells at a density of approximately 114.36 × 10⁴ cells/mL was added to each of the exposure flasks. This inoculum provided the required cell density of approximately 1.0 × 10⁴ cells/mL. At each subsequent 24-hour interval, a single cell count was conducted on each replicate solution of the treatment and control vessels using a haemacytometer and a compound microscope. One sample was removed from each flask for counting. One or more haemacytometer fields, each 0.10 × 0.10 cm in surface area and 0.010-cm deep and containing 0.00010 mL of culture, were examined for each sample until at least 400 algal cells or four fields were counted. Observations of the health of the algal cells were also made at each 24-hour interval. Due to the nature of Navicula pelliculosa cells to cluster together, each test solution was vigorously pipetted to distribute the cells prior to removing a sample for cell counts and observations.

Based on the decline in test solution concentration over the 96 hours of exposure and OCSPP 850.4500 guidance for pesticides, results are based on initial measured concentrations.

Under the conditions of the study, the 96-hour NOEC and LOEC values for yield were determined to be 0.36 and 0.73 mg/L, respectively. Based on initial measured concentrations, the 96-hour EC50 value for yield was determined to be 1.9 mg/L with 95 % confidence limits of 1.4 to 2.1 mg/L. The 96-hour NOEC and LOEC values for growth rate were determined to be 0.36 and 0.73 mg/L, respectively. Based on initial measured concentrations, the 96-hour EC50 value for average specific growth rate was determined to be 3.3 mg/L with 95 % confidence limits of 3.1 to 3.5 mg/L. The 96-hour NOEC and LOEC values for AUGC were determined to be 0.36 and 0.73 mg/L, respectively. The 96-hour EC50 value for AUGC was determined to be 2.4 mg/L with 95 % confidence limits of 2.2 to 2.6 mg/L.

 

In a study reported by Softcheck (2014), the toxicity of the test material to the freshwater cyanobacteria, Anabaena flos-aquae, was investigated under GLP conditions and in accordance with the standardised guidelines OCSPP 850.4550.

An inoculum of 2.90 mL of Anabaena flos-aquae cells at a density of approximately 34.5 × 10⁴ cells/mL was added to each of the exposure flasks (100 mL/flask). This inoculum provided the required cell density of approximately 1.0 × 10⁴ cells/mL. At each subsequent 24-hour interval, a single cell count was conducted on each replicate solution of the treatment and control vessels using a haemacytometer and a compound microscope. Two samples were removed from each flask for counting. One or more haemacytometer fields, each 0.10 × 0.10 cm in surface area and 0.010-cm deep and containing 0.00010 mL of culture, were examined for each sample until at least 400 algal cells or four fields were counted. Observations of the health of the algal cells were also made at each 24-hour interval. Due to the nature of Anabaena flos-aquae cells to cluster together, each test solution was vigorously pipetted to distribute the cells prior to removing a sample for cell counts and observations.

Based on the decline in test substance concentrations over the 96-hour exposure period and OCSPP 850.4550 guidance for pesticides, results are based on initial measured concentrations.

Following a 96-hour exposure of Anabaena flos-aquae to test material, the resulting EC50 values for yield, average specific growth rate and area under the growth curve were 2.1, 4.2 and 2.2, respectively. The 96-hour NOEC and LOEC values for yield, average specific growth rate and area under the growth curve were 1.1 and 2.9 mg/L, respectively.

 

In a study reported by Thompson (1985), the toxicity of the test material to the unicellular green alga, Selenastrum capricornutum, was investigated under GLP conditions and in accordance with the standardised guidelines OECD 201 and EPA OPPTS 850.5400.

Under the conditions of the study, the 72 hour EC50, in terms of growth rate, was 1.7 mg/L; the NOEC was 0.66 mg/L. These values were based on the mean measured concentrations of the test material, compared with the solvent control.