Acetophenone

Endpoint summary

Additional information

The experimental determined reaction rate constant for the reaction of acetophenone with OH radicals in the gas-phase is reported to be 2.74 x 10E-12 cm³/molecule x s. Taking into account a OH radical concentration of 5 x 10E5 radicals/cm³ (24 h day) a tropospheric half-life t1/2=5.86 d can be calculated. Acetophenone is resistant to hydrolysis under environmental conditions.

In a study conducted according to OECD Guideline 301C, acetophenone proved to be readily biodegradable and fulfilling the 14 d window criterion (64.7% biodegradation after 14 d). A number of supportive studies confirm this result obtained at the well-known stringent conditions of the MITI Test (very high ratio substance/inoculum). Under anaerobic conditions, acetophenone was biodegraded neither in the standard test nor in the low concentration test in appreciable amounts (general: 30% biodegradation after 28 d; in the low concentration test: 15% degradation after 28 d, value taken from a figure). In tests conducted using freshwater and marine sediments and anaerobic conditions, 2-CAP was transformed via electron transfer to acetophenone and subsequently to sec.-phenylethyl alcohol as could be determined via HPLC and GC/MS. Based on the temperature studies, the conversion of 2-CAP to acetophenone and subsequently sec.-phenylethyl alcohol occured via abiotic reactions (metallocoenzyms). Two simulation test on biodegradation in surface waters are available: In a study conducted according to the standard BOD technique (APHA (1980) and using three different inoculum sources (ground water, river water, and harbour water), acetophenone biodegradation and the corresponding half-lives were in the range between ca. 40 and 82% and 4 (harbor water), 8 d in river water, and 32 d (ground water), respectively. The authors assumed, that the observed high biodegradation rate of acetophenone using harbour water as inoculum may be due to the fertility and/or the presence of microorganisms that were pre-exposed to the test chemical or similar chemicals. In another study, the biodegradation of acetophenone was investigated using Ohio River water as inoculum. The biodegradability was followed by determination of carbon dioxide production. After 10 d, samples were redosed to check possible acclimation. Initially, a lag phase of about three days was observed. Thereafter acetophenone was biodegraded relative quickly: ca. 50% degradation after 6 days based on CO2 production due to oxidation of test item and ThCO2 production. Redosing after 10 days resulted in rapid degradation: ca. 50% were degraded after 3 days. A bioconcentration factor BCF=0.4749 was calculated using EPIWIN v3.20, BCFWIN v2.17. Based on this result, no significant bioconcentration of acetophenone in aquatic species is to be expected. According to the available and reliable data obtained via guideline studies, the soil sorption coefficient Koc for acetophenone was determined to be in the range between 9 and 95. According to the classification of Blume & Ahlsdorf, acetophenone can be regarded as a substance with very low to low binding strength to organic matter of soil and sediments. Based on the physical-chemical properties the environmental distribution was calculated using Mackay Level I. According to the calculation water is the main target compartment (96%) and to a minor extent air (2.9%). The other compartments were not relevant (in total ca. 1%).

The experimentally derived Henry's Law constants were in the range between 0.92 and 1.08 Pa m³/mol at 25°C. Based on the results of Betterton 1991, the Henry's Law constant at 20°C was calculated to be 0.766 Pa m³/mol. The results indicate that acetophenone can be regarded as moderately volatile from aqueous solution.

Most of the monitoring data compiled in the IUCLID were sampled and analysed between 1970 and 2000. Current studies dealing with the occurrence of acetophenone in the environment are scarce. Acetophenone was detected in surface waters samples collected from 139 streams (max. 0.41 µg/L, median: 0.15 µg/L; USA, 1999 -2000). Furthermore, acetophenone was identified but not quantified in ground water samples at and near a landfill (USA, 2000). There are hints that acetophenone occurs naturally in the environment.