2-butyloctanoic acid

Endpoint summary

Description of key information

For the terrestrial compartment, a microorganism study, a chronic earthworm study and a plant study are available for 2 -butyloctanoic acid.

The effects of 2 -butyloctanoic acid on the metabolic activity of soil micro-organisms were determined according to OECD Guideline 216.

The derived EC10 value was as follows: 354 mg/kg soil dry weight on day 28 and the EC50 for microbial nitrate transformation was determined to be 828 mg/kg soil dry weight on day 28.

The following EC, LOEC, NOEC-values were calculated from an Earthworm Reproduction Study with 2 -butyloctanoic acid according to OECD 222: NOEC (mortality) ≥ 120 mg/kg soil dw, LOEC (mortality) > 120 m/kg soil dw, NOEC (reproduction) = 30 mg/kg soil dw, LOEC (reproduction) = 60 mg/kg soil dw, EC10 (reproduction) =  43.4 mg/kg soil dw, EC20 (reproduction) =  66.7 mg/kg soil dw, EC50 (reproduction) > 120 mg/kg soil dw.

The effects of 2 -butyloctanoic acid to terrestrial plants were determined in 6 species in seedling emergence and seedling growth test according to OECD Guideline 208. Species lettuce was the most sensitive species, the following values were calculated for shoot fresh weight: NOEC = 62.5 mg/kg dw, LOEC = 125 mg/kg dw, EC50 = 133 mg/kg dw.

Additional information

The effects of 2 -butyloctanoic acid on the metabolic activity of soil micro-organisms were determined according to OECD Guideline 216.The test item was applied via quartz sand at concentrations of 1000 - 316 - 100 - 31.6 - 10 mg/kg soil dry weight (factor√10). Untreated field soil, adjusted to a moisture content corresponding to nominally 45 % of its maximum water holding capacity and mixed with a source of organic nitrogen (lucerne-greengrass-meal), was tested as the control under the same test conditions as the test item replicates.Measurements of nitrate-nitrogen concentrations in soil were made in all treatments and the control on the day of treatment application (day 0) and after 7, 14 and 28 days. The derived EC10 values were as follows: 161 mg/kg soil dry weight on day 7, 387 mg/kg soil dry weight on day 14, and 354 mg/kg soil dry weight on day 28.

The Earthworm Reproduction Study was performed with 2 -butyloctanoic acid according to OECD Guideline 222.

Neither evident earthworm mortalities (< 10%) nor evident pathological symptoms or changes in the behaviour of adult earthworms were observed in the control and the test item concentrations 7.5 to 120 mg test item/kg SDW. There were no statistically significant differences in earthworm biomass at all test item concentrations compared to the pooled control. After a further four weeks, the reproduction rate (average number of juveniles produced) was 105 in the pooled control and ranged from 65 to 114 in the test item treatment rates. There were no statistically significant differences in earthworm reproduction in the treatment rates 3.75 to 30 mg test item/kg SDW compared to the pooled control. However, at the test item concentrations 60 and 120 mg test item/kg SDW the earthworm reproduction was statistically significantly reduced. The following EC10 value was calculated: EC10 (reproduction) =  43.4 mg/kg soil dw (95% confidence interval: 13.8 - > 120 mg/kg soil dw).

The phytotoxicity of the test item to six terrestrial plant species was determined according to OECD 208 (July 2006) at the test facility in seedling emergence and seedling growth tests over a period of 21 days. For onion 50 % emergence of the control seedlings was reached after 14 days. Therefore, the test for onion was prolonged until day 28.

Test systems comprised two monocotyledon (oats, Poaceae; onion, Amaryllideaceae), and four dicotyledons (sugar beet, Amaranthaceae; rape, Brassicaceae; lettuce, Asteraceae; soybean, Fabaceae). The test was conducted with various test concentrations:

Oats, onion, lettuce, soybean: 1000 - 500 - 250 - 125 - 62.5 mg/kg DW (factor 2)

Sugar beet, rape: 1000 - 400 - 160 - 64 - 25.6 - 10.24 mg/kg DW (factor 2.5)

The test item was incorporated into the soil in which the seeds were sown. The test containers were bottom watered with nutrient solution as needed.

Potential toxic effects of the test item were assessed on day 7, 14 and 21 (onion additionally on day 28) by visual observations (number of emerged seedlings and phytotoxic effects) and at test end by shoot height and shoot fresh weight determination.

The number of emerged seedlings was effected in species lettuce, no seedlings emerged at concentrations > 250 mg/kg dw, with NOEC being 125 mg/kg dw. In all other species the number of emerged seedlings were not effected up to the highest test substance concentration.

The shoot height was most severly effected for species soybean and lettuce, the following values were derived:

Soybean: NOEC = 62.5 mg/kg dw, LOEC = 125 mg/kg dw, EC25 > 1000 mg/kg dw, EC50 > 1000 mg/kg dw.

Lettuce: NOEC = 125 mg/kg dw, LOEC = 250 mg/kd dw, EC25 = 192 mg/kg dw (95% cl 123 - 250 mg/kg dw), EC50 > 250 mg/kg dw.

Species lettuce was the most sensitive species for shoot fresh weight, the following values were calculated: NOEC = 62.5 mg/kg dw, LOEC = 125 mg/kg dw, EC 25 = 69.9 mg/kg dw (95% cl < 62.5 - 100 mg/kg dw), EC50 = 133 mg/kg dw (95% cl 91.5 - 196 mg/kg dw).