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This summary information about persistence, bioaccumulation and toxicity comes from Fass. The risk comes from the reports by Goodpoint.

Persistence. Naproxen is slowly degraded in the environment.
Bioaccumulation. Naproxen has low potential for bioaccumulation.
Toxicity. Naproxen has high chronic toxicity.
Risk. The use of naproxen has been considered to result in low environmental risk (year 2019).

Detailed information

Comment on Fass environmental information

Naproxen has different classifications on fass.se. According to Lif (the trade association for the research-based pharmaceutical industry in Sweden) the various pharmaceutical companies compile environmental information for their active substances based on internal studies and published data. Based on data, which may thus differ between different pharmaceutical companies, the companies assess the environmental risk with guidance from “Environmental classification of pharmaceuticals at www.fass.se – Guidance for pharmaceutical companies 2012”. The Swedish Environmental Institute (IVL) reviews the assessment but does not have the task of coordinating/harmonizing environmental information from different pharmaceutical companies for the same active substance.

Fass environmental information Naprosyn Entero

Fass environmental information for Naprosyn Entero (naproxen) from Pharmanovia (downloaded 2021-07-02).


Persistence: "Naproxen is not readily biodegradable, however, it is inherently biodegradable and actual, measured elimination rates in various sewage works range from 0% to >99%, with a median of approximately 67%. Moreover, naproxen in surface waters is short-lived, due to biodegradation and photolysis in superficial layers (which is not included in the above PEC calculation). A surface water half-life in late summer in Switzerland at ~47° N was determined at 14 days. Hence, naproxen is rapidly degraded in sewage works and surface waters and is nonpersistent. [...] Naproxen is slowly degraded in the environment."

Bioaccumulation: "log D values below 1.1 at pH 6.5–7.4."

Toxicity: There are data for 3 trophic levels, most sensitive crustacean NOEC (Ceriodaphnia dubia) NOEC = 32 microg/L.


PEC/PNEC is based on sales data in Sweden in year 2010. PEC/PNEC = 0.92 which gives the risk low.

Fass environmental information Vimovo

Fass environmental information for naproxen from Vimovo (esomeprazole, naproxen) from Grunenthal Sweden (downloaded 2021-07-02).


Persistence: "Naproxen is classified as not readily biodegradable; however, results show that after a lag phase in an OECD 301B and OECD 301F (Refs. 32, 35) naproxen undergoes almost complete primary biodegradation in the presence of sewage sludge. Naproxen was also rapidly degraded in aquatic sediments in an OECD 308 preliminary test (up to 40% mineralisation after 14 days, Ref. 33) but in comparison was relatively stable in water in an OECD 309 test (Ref. 31). Overall the weight of evidence suggests that the presence of sludge and sediment plays an important role in the biotransformation of naproxen in the environment, and the phrase ‘Naproxen is slowly degraded in the environment’ reasonably reflects the available data."

Bioaccumulation: "BCF = 22–28 L/Kg after 14 days uptake."

Toxicity: here are data for 3 trophic levels, most sensitive crustacean (Daphnia magna) "21 day NOEC (survival, reproduction, growth)" = 150 microg/L.


PEC/PNEC is based on sales data in Sweden in year 2016. PEC/PNEC = 0.24 which gives the risk low.

Pharmaceuticals in the aquatic environment

Analyzes of pharmaceuticals in the aquatic environment in Region Stockholm. Naproxen has been detected in treated wastewater and surface water in Region Stockholm during 2012–2016. Naproxen has also been detected in treated wastewater at measurements 2017.

Report Goodpoint 2016

Large margin in Sweden between concentrations in the environment and the concentration that affects the environment.

Report Goodpoint 2019

Comparative assessment of environmental risk when using diclofenac, naproxen, ibuprofen, ketoprofen, etoricoxib, celecoxib and paracetamol from a Swedish perspective (Report Goodpoint 2019). From an environmental risk point of view, the exchange of diclofenac is recommended for any of the other investigated NSAIDs/analgesics. [...] Paracetamol is a very safe alternative from an environmental point of view. The others are also considered to pose low environmental risk, but slightly increased for ketoprofen. The risk factors for ketoprofen, naproxen, ibuprofen, celecoxib, etoricoxib and paracetamol are not considered so great that an exchange with another substance is recommended. Environmental measurements as well as efficacy studies of both celecoxib and etoricoxib are required."

Author: Health and Medical Care Administration, Region Stockholm