Paracetamol

Biodegradation in water: screening tests

Description of key information

The half life period of Paracetamol in water is 15 days and based on this value it can be concluded that the chemical is not persistent in water medium since the half  life is less than the threshold of 60 days (to qualify the chemical as persistent). Also the diffusion percentage of Paracetamol in water medium is 22%. This coupled with the dilution of water shall result in ready biodegradability of the chemical.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

No. of studies were reviewed for Biodegradation in water from reliable sources having Klimisch rating 2.

The summary of the results are presented below

Based on prediction by PBT profiler, Office of Chemical Safety and Pollution Prevention , U.S. Environmental Protection Agency; version 1.301 the half life period of Paracetamol in water is 15 days and based on this value it can be concluded that the chemical is not persistent in water medium since the half life is less than the threshold of 60 days (to qualify the chemical as persistent). Also the diffusion percentage of Paracetamol in water medium is 22%. This coupled with the dilution of water shall result in ready biodegradability of the chemical.

QSAR version3.1 estimated the biodegradtion to be 67.355 % in 28 days.

Study conducted by Lili Zhang et.al (Appl Microbiol Biotechnol (2013) 97:3687–3698) on three strains ofStenotrophomonas sp.Found paracetamol to be readily biodegradable considering Toc values as well as oxygen consumption values. Individual stranis f1, f2, and fg-2 as well as the coculture could perform complete degradation of paracetamol at concentrations of different concentrations in a over all duration of 7.5 days.

Another publication by Tsung-Hsien et.al,presenting a batch experiment results, acetaminophen was characterized by significant biodegradability, weak desorption and strong sorption. Therefore resulting in 100% removal after 8 days via sorption and >25% removal by biodegradation after 2 days. Moreover, the half-life via bio-sorption/degradation for acetaminophen was 0.6 days. Based on the kinetic rate constants for degradation of acetaminophen, the substance is most probably readily biodegradable.

Based on the study conducted by : K.-P. Henschel et.al( REGULATORY TOXICOLOGY AND PHARMACOLOGY 25, 220–225 (1997)In the ready biodegradability test according to OECD guideline 301F, 57% of paracetamol was degraded to 57% after 28 days of incubation with activated sludge from a sewage treatment plant. However, it was not mentioned in the result how much that had been degraded within the 10-day window that should be used as a guidance for classifying compounds as readily biodegradable. Hypothetically, the compound was therefore based on the 57% degradation after 28 days considered as readily biodegradable. However, paracetamol was only moderately biodegradblebiodegradable since less thnthan the 60% removal was obtainedattained within 28 days.

Based on the weight of evidences used for the target chemical Paracetamol it was found that the degradation percentage of Paracetamol in water medium is ranging between 50 to 67.355%.This leads to the conclusion that the substance is readily biodegradable in water.