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Toxicity to microorganisms

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Description of key information

Based on the prediction done using the OECD QSAR toolbox version 3.3 with log kow as the primary descriptor and considering the closest read across substances, the toxicity to micro-organisms was predicted 1-(4-methoxyphenyl)propan-2-one (CAS: 122-84-9). IGC50 growth value was estimated to be 209.582 mg/l for Tetrahymena pyriformis for 48 hrs duration. It was concluded that 1-(4-methoxyphenyl)propan-2-one (CAS: 122-84-9) was likely to be not toxic to micro-organisms.

Key value for chemical safety assessment

EC50 for microorganisms:
209.582 mg/L

Additional information

Following studies of target chemical and structurally similar read across includes predicted data and experimental data to conclude the toxicity extent of 1-(4-methoxyphenyl)propan-2-one (CAS: 122-84-9) towards micro-organisms is summarized as follows:

Based on the prediction done using the OECD QSAR toolbox version 3.3 with log kow as the primary descriptor and considering the closest read across substances, the toxicity to micro-organisms was predicted 1-(4-methoxyphenyl)propan-2-one (CAS: 122-84-9). IGC50 growth value was estimated to be 209.582 mg/l for Tetrahymena pyriformis for 48 hrs duration. It was concluded that 1-(4-methoxyphenyl)propan-2-one (CAS: 122-84-9) was likely to be not toxic to micro-organisms.

The above predicted data of target chemical is supported by the experimental study of structurally similar read across 2 -octanone (CAS No. 111-13-7) from the publication Toxicology Methods 1997, suggests that the Toxicity to micro-organisms study was conducted onTetrahymena pyriformisstrain GL for 72 hrs.

The assay was conducted in a buffered medium under static conditions.

 Stock solutions of test chemical was prepared either in solvent DMSO or in distilled water.The solvent DMSO has low toxicity toTetrahymena,low volatility, and high ability to dissolve organic chemicals. Concentration not greater than 0.75% DMSO (350 µL per 50 mL of medium) are used. This conc. was shown to have no effect onTetrahymenapopulation growth. Standard stocks are prepared on a milligram per liter basis.

 When using distilled water for prepare stock solutions, extra care must be taken to maintain sterility.

Tests were conducted in a 250 mL Erlenmeyer flask containing 50 mL of sterile, semidefined proteose – peptone – based medium and five different conc. of test substance. Then the flasks were inoculated with log-growth-phase culture ofTetrahymena pyriformisof initial cell density of approx. 2500 cells/ml and incubated for about 40 hrs at27 ± 1ᵒC with pH 7.4. After incubation, growth inhibition was measured spectrophotometrically or by electronic particle counting and 50% effect levels are determined at 72 hrs.

 The nutritional requirement of test organism was met by a solution of proteaose-peptone, yeast extract, glucose, and Fe-EDTA. For test bacterial strain, the optimum temp. for growth was in between 27ᵒC and 35ᵒC and pH range is 5.0 – 8.6, with the optimum pH being 7.5, respectively.

Control test vessel contains the test medium inoculated with the test organism with no addition of test chemical and blank was also prepared for the study.

The 50% inhibitory growth concentration in mg/l (IGC50) and the 95% fiducial interval are determined for each test compound. The IGC50 was calculated with the probit procedure.

Thus, based on growth inhibition of test organism, for 2 -octanone the IGC50 value was found to be 181.1 and 90.7 mg/l, respectively.