Paracetamol

Endpoint summary

Additional information

Stability

Phototransformation in air

The atmospheric oxidation half-life of Paracetamol was estimated using the level III multimedia model. It was estimated that the substance is not persistent in air medium as the half life period of paracetamol in air is only 0.92 days. This indicates that paracetamol is easily photo transformed in air and shall photodegrade rapidly.

OVERALL OH Rate Constant = 0.000000000018 cm3/molecule-sec.

Hydrolysis

The Hydrolysis rate constant of paracetamol is estimated to be 0.0000000000176761 cm3/molecule-sec. at half life of 7.261 hrs.The estimated half life of the substance indicates that the substance is moderately hydrolysable.

Phototransformation in water

No experimental data available. As this study is not a standard information requirement in REACH and there is no indication from the CSA on the need to investigate further the fate and behaviour of the substance (Annex X requirement), no further testing is considered necessary.

Phototransformation in soil

No experimental data available. As this study is not a standard information requirement in REACH and there is no indication from the CSA on the need to investigate further the fate and behaviour of the substance (Annex X requirement), no further testing is considered necessary.

Biodegradation

Biodegradation in water

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

The summary of the results are presented below

Sr.No	Endpoint	Percentage Degradation	Half - Life	Parameter	Sources
1	Ready biodegradability	50% degradation	15 days	Half-life	Predicted data from PBT profiler
2	Ready biodegradability	67.355 % degradation	-	O2 consumption	Predicted data from QSAR

 

By applying weight of evidence approach to 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. 

Biodegradation in water and sediment

Based on the Level III Fugacity Model, the half life period of theParacetamolwas estimated. The half period of paracetamolin water is 15 days (360 hrs) therefore it is considered that the substance will qualify as not persistent as the half life does not exceed the threshold of 60 days. So, it can be confirmed that the substance is readily biodegradable in water medium where as in sediment medium it is persistent as the half life is 140 days.

However, since there is no diffusion of the substance in the sediment as evident from the reported data (0% in sediment) and hence persistence in the sediment compartment is not likely to be critical.

Media	Half-Life  (days)	Percent in Each Medium
Water	15	22%
Sediment	140	0%

Biodegradation in soil

The PBT Profiler & EPI Suite has estimated that Paracetamol is expected to be found predominantly in soil and its persistence estimate is based on its transformation in this medium. Its half-life in soil, 30 days (720 hrs). does not exceeds the threshold of 120 days as per Annex XIII of REACH.Therefore, paracetamol is estimated to be not persistent in the soil environment.

PBT profiler estimate

Media	Half-Life  (days)	Percent in Medium
Soil	30	78%

 EPI Suite

	Mass Amount (percent)	Half-Life (hr)	Emissions (kg/hr)
Soil	77.6	720	1000

 

	Fugacity (atm)	Reaction (kg/hr)	Advection (kg/hr)	Reaction (percent)	Advection (percent)
soil	2.84e-016	1.6e+003	0	53.3	0

 

Bioaccumulation

No. of studies of target substance Paracetamol were reviewed for bioaccumulation from reliable sources having Klimisch rating 2 .

The summary of the results are presented below

 

Sr.No	Endpoint	Effect values	Interpretation of results	Species	Sources
1	BCF	3.2	Non -bioaccumulative	Fish	Predicted data from PBT
2	BCF	3.162	Non -bioaccumulative	Fish	Predicted data from EPI Suite
3	BCF	12.671	Non -bioaccumulative	Cyprinus carpio	Predicted data from QSAR

 

By applying weight of evidence approach to the target substance Paracetamol,the endpoint value of bioaccumulation was found to vary between BCF = 3.162 to 12.671 in fish (Cyprinus carpio).Thus it is concluded that the test substance Paracetamol is not expected to bioaccumulate in the food chain because it does not exceed the BCF criteria of 2000.

Transport and distribution

Adsorption/desorption

Soil Adsorption Coefficient i.e Koc value of paracetamol was estimated as 45.09 L/kg by means of MCI method.This indicates that paracetamol will have low tendency of sorption to soil and sediment and therefore have moderate migration potential to groundwater.This Koc value when converted at 20 degC is equivalent to 36.072.

Henry's Law constant

Henry's Law states that at a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid.Henry’s law constant of Paracetamol was estimated to be 0.0000000651 Pa m³/mol at 25 degC.