This summary information comes from Fass and the risk from the report from Goodpoint.
Persistence. Diclofenac is slowly degraded in the environment
Bioaccumulation. Diclofenac has low potential for bioaccumulation
Toxicity. Diclofenac has moderate chronic toxicity.
Risk. See below.
Diclofenac is not recommended in the Wise list (a list of recommended pharmaceuticals from the Stockholm Drug and Therapeutics Committee).
Fass environmental information for Voltaren (diclofenac) from Novartis (downloaded 2020-10-20) with environmental risk calculated from sales data 2018. Fass environmental information from GlaxoSmithKline Consumer Healthcare (2020-10-20) is also available but the environmental risk there is calculated from sales data 2016.
Persistence: "While the results from Kunkel 2008 would even justify the statement "diclofenac is degraded in the environment", the fact that no standard OECD308 study is available has led to a more conservative assumption."
Bioaccumulation: BCFss = 3–5 (OECD305, 1996; Harlan Laboratories Study D24068).
BCF (plasma) = 5–11 "(mean measured plasma concentration/mean exposure concentration in rainbow
trout (Oncorhynchus mykiss) exposed to sewage effluents at three sites) (Brown et al., 2007)."
BCF (plasma) = 2.5–29 "(measured fish plasma levels/average measured water concentration after 14 days of exposure) (Fick et al., 2010)."
Chronic toxicity: There are NOEC for 3 trophic levels, lowest NOEC for fish (OECD210, Danio rerio, 34 days) 0.32 mg/L.
PEC/PNEC is based on sales data in Sweden in year 2018. PEC/PNEC = 0.03 which gives the risk insignificant, i.e. consideration has not been given to measured levels in the environment.
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."
The acute toxicity to aquatic organisms is assessed as high. Due to the risk of ecotoxicity in water, diclofenac has previously been monitored within the framework of EU water legislation. There is now enough data to assess whether diclofenac is to be proposed as a priority substance when the European parliament and the Council next time proposes a revised directive regarding priority substances in the field of water policy. For Sweden, the Swedish Agency for Marine and Water Management has diclofenac among special pollutants in its regulation HVMFS 2013:19 (Updated 2017-01-01).
The degree of purification of diclofenac in the Swedish treatment plants is low, i.e. most of the substance comes out in our nature. In Sweden diclofenac is found in surface water at levels reported to have effects on fish.
Diclofenac is included in Region Stockholm's list of pharmaceuticals with risk for negative environmental impact according to the environmental program 2017–2021 based on lowest effect concentration, LOEC = 1 microg/L, and concentrations found in the environment. Diclofenac has been detected in treated wastewater and surface water in Region Stockholm.
In India and Pakistan several species of vultures have been endangered because of the veterinary use of diclofenac when the dead cows for cultural reasons is left to the vultures. In recent years the same problem has been seen in eagles in same areas. Similar effects on vultures and eagles are also suspected in Africa and there is even some concern in Europe for example in parts of Spain, where carcasses are left in the open for wild animals to eat.
Diclofenac can be purchased without prescription in Sweden. Since 3 October 2018, all pharmacies inform customers about diclofenac's negative impact on the environment.
Buying diclofenac without prescription is questioned again (2018-10-04) for medical reasons and for environmental reasons.
Diclofenac has been associated with a greater risk of serious cardiovascular events than other COX inhibitors in several studies. The Swedish Medical Products Agency decided that tablets and capsules containing diclofenac should be reclassified as precription-only medicine from 1 June 2020 due to the risk of cardiovascular adverse events. Topical preparations without prescription are not affected by the decision.
Concrete proposals on how to work to reduce emissions of environmentally harmful pharmaceuticals on the list have been developed in close cooperation with the Stockholm Drug and Therapeutics Committee's expert groups. The action proposals were developed from an environmental perspective. The patient's best always goes first and several pharmaceuticals on the list are also included in the Wise list. However, for such pharmaceuticals, there may be measures that could reduce the environmental impact.
Concrete proposal for diclofenac
Author: Health and Medical Care Administration, Region Stockholm