Q.01

What are environmental quality standards for surface water?

In the EU, environmental quality standards (EQS) are legally binding concentration limits for pollutants in surface water, sediment or fish and other biota. The Water Framework Directive (WFD, 2000/60/EC) defines an EQS as "the concentration of a particular pollutant or group of pollutants in water, sediment or biota not to be exceeded in order to protect human health and the environment" (Art. 2(35)) [1]. The values themselves are in Annex I Part A of the EQS Directive (2008/105/EC). That annex was rewritten by Directive (EU) 2026/805, which adds 25 new substances and tightens 14 existing standards, with effect from 22 December 2027.

Approach: I read the consolidated WFD and the EQS Directive's priority-substance table in the version in force from the 2013 amendment, then the adopted text of the 2026 amending directive as the Council published it (PE-CONS 18/26). I couldn't open the Official Journal version on EUR-Lex (ELI link), so page references below are to the Council PDF.

How EQS work

  • Two forms of standard for water:
    • AA-EQS (annual average): at each representative monitoring point, the average of the year's measurements must not exceed the standard.
    • MAC-EQS (maximum allowable concentration): no single measurement may exceed it. Where a MAC-EQS is "not applicable", the AA-EQS is considered protective against short peaks (PDF pp. 197, 203).
  • Biota and sediment standards: where Annex I gives one, Member States "shall apply" it instead of the water EQS (Art. 3(2) as amended, p. 112). Biota standards refer to fish unless stated otherwise (p. 197).
  • Two water categories:
    • "Inland surface waters": rivers and lakes, plus related artificial or heavily modified water bodies.
    • "Other surface waters": transitional and coastal waters. These usually have stricter values (p. 197).
  • Link to chemical status: a water body has good chemical status only if it meets the EQS for priority substances, the EQS for river basin specific pollutants, and any effect-based trigger values (WFD Art. 2(24)) [1].
  • Link to industrial permits: these EQS also count as EQS under the Industrial Emissions Directive (WFD Art. 22(4)) [2]. Where an EQS requires stricter conditions than best available techniques would give, "more stringent emission controls shall be set" (WFD Art. 10(3)) [3].

The values before the 2026 revision (45 priority substances, 2013 version)

Some examples (AA inland / AA other / MAC inland / MAC other / biota):

  • Benzene: 10 / 8 / 50 / 50 µg/l [4]
  • Cadmium: five water-hardness classes, AA inland from ≤ 0,08 up to 0,25 µg/l [5]
  • Mercury: biota EQS of 20 [6]
  • PFOS: 6,5 × 10⁻⁴ / 1,3 × 10⁻⁴ / 36 / 7,2, with biota 9,1 [7]

What Directive (EU) 2026/805 changes (adopted 30 March 2026)

1. Revised EQS for 14 existing substances (entries 5, 9, 13, 15, 17, 21, 23, 24, 28, 30, 34, 37, 41 and 43). They take effect from 22 December 2027, with good status for them to be achieved by 22 December 2033 (Art. 3(1a)(iii), p. 109). Some examples:

Substance2013 valueNew value (pp. 173-187)
Chlorpyrifos, AA inland0,03 [8]4,6 × 10⁻⁴ µg/l
Diuron, AA / MAC inland0,2 / 1,8 [9]0,049 / 0,27 µg/l
Mercury, biota20 [6]11 µg/kg
Nickel, AA / MAC inland4 / 34 [10]2 (bioavailable) / 8,2 µg/l
Fluoranthene, biota30 [11]6,1 µg/kg (crustaceans and molluscs)
Cypermethrin, AA inland8 × 10⁻⁵ [12]3 × 10⁻⁵ µg/l

2. 25 new priority substances (entries 46 to 70). They take effect from 22 December 2027, with good status by 22 December 2039. Member States must set up a supplementary monitoring programme by 22 December 2027 and a preliminary programme of measures by 22 December 2030 (Art. 3(1a)(iv), p. 110). Values below are AA-EQS for inland waters in µg/l (pp. 188-196):

GroupSubstances (AA inland, µg/l)
Hormones17α-ethinylestradiol (EE2) 1,7 × 10⁻⁵; 17β-estradiol (E2) 0,00018; estrone (E1) 3,6 × 10⁻⁴
Pharmaceuticalsazithromycin 0,019; carbamazepine 2,5; clarithromycin 0,13; diclofenac 0,04; erythromycin 0,5; ibuprofen 0,14
Neonicotinoidsacetamiprid 0,037; clothianidin 0,01; imidacloprid 0,0068; thiacloprid 0,01; thiamethoxam 0,04
Pyrethroidsbifenthrin 9,5 × 10⁻⁵; deltamethrin 1,7 × 10⁻⁶; esfenvalerate 1,7 × 10⁻⁵; permethrin 2,7 × 10⁻⁴
Other pesticides and biocidesglyphosate 0,1 in freshwater used for drinking-water abstraction, 86,7 in other freshwater; nicosulfuron 0,0087; triclosan 0,02
Industrial substances and metalsbisphenol A 1,7 × 10⁻⁴; silver 0,01
Group sumsPFAS, sum of 25 (including TFA): 0,0044 µg/l as PFOA-equivalents, biota 0,077 µg/kg. The biota EQS is the critical one and "must therefore be complied with" (footnote 27, p. 202). PFOS is now covered by this sum. Sum of pesticides: 0,2 µg/l, excluding entries 16, 30, 34, 44 and glyphosate.

3. Six substances moved out of the priority list. Alachlor, atrazine, carbon tetrachloride, chlorfenvinphos, simazine and trichlorobenzenes move to a new Annex II Part C, a repository of harmonised EQS for river basin specific pollutants. Their values stay the same; for example, atrazine remains 0,6 / 0,6 / 2,0 / 2,0 µg/l (pp. 207-208).

4. National pollutants (new Art. 8d).

  • Member States "shall set and apply EQS" for river basin specific pollutants that pose a risk in their territory.
  • They must notify their lists to the Commission by 22 December 2027.
  • Union-level Part C values take precedence over national ones (p. 131-132).

5. Other changes:

  • Effect-based monitoring of estrogenic substances runs for two years from 1 January 2030 (p. 121).
  • The watch list can hold up to 10 substances and is to include microplastics and indicators of antimicrobial resistance (pp. 123-124).
  • Bisphenols, pesticides by mode of action and pharmaceuticals by mode of action are listed for review (Annex III, p. 210).

Timing:

  • Member States must transpose the directive by 21 December 2027 (Art. 4, p. 135).
  • The consolidated WFD is now dated 10 May 2026 and already reflects the amendments [13].
  • The Commission's next review of the priority list and its EQS is due by 11 May 2032 (WFD Art. 16(2)) [14].

I can also pull how a Member State has transposed these standards (for example Germany's surface water ordinance, the OGewV) or the US EPA's national recommended water quality criteria for comparison.

Sources:

Q.02

How do the EU and UK limits differ?

Great Britain still uses the EU priority-substance limits from 2013. Directive (EU) 2026/805 does not apply there, so the two regimes match today and split from 22 December 2027. From that date the EU has tighter limits for 14 existing substances and 25 new ones, and Great Britain has no update in force. For Scotland this is written into the law: its 2024 Standards Directions define the Priority Substances Directive (2008/105/EC) "as it had effect immediately before exit day" (Scotland Standards Directions 2024, p. 2).

Approach: Our datasets hold the EU priority-substance table but no UK surface-water standards. For the UK side I used the Environment Agency's current EQS spreadsheets for England, Scotland's 2024 Directions, and DAERA's page on Northern Ireland. I couldn't open the England and Wales 2015 Directions or the Northern Ireland Regulations on legislation.gov.uk.

Where the UK stands

  • England (Environment Agency): The EQS lists for permit risk assessments were last updated 20 February 2026 (guidance page). The legal source is the Water Framework Directive (Standards and Classification) Directions (England and Wales) 2015 (legislation.gov.uk), which I couldn't open.
  • Scotland: The Scotland River Basin District (Standards) Directions 2024 came into force on 1 February 2025 and replaced the 2014 Directions (pp. 1, 4). They apply only "in so far as they are consistent with" the retained directives (p. 2).
  • Northern Ireland: DAERA says Directives 2008/105/EC and 2013/39/EU are transposed by the Water Framework Directive (Classification, Priority Substances and Shellfish Waters) Regulations (Northern Ireland) 2015 (DAERA). The page does not mention any later EU amendment. I couldn't confirm from an official source whether the Windsor Framework brings Directive 2026/805 into Northern Ireland.

Today: priority substances are the same

The England values match the EU 2013 Annex I Part A table for every substance I checked (µg/l unless noted):

SubstanceEU 2013England (EA)
Benzene, AA inland / AA other / MAC10 / 8 / 50 [4]10 / 8 / 50
Cadmium, AA inland (by water hardness) / AA other≤ 0,08 to 0,25 / 0,2 [5]≤ 0.08 to 0.25 / 0.2
Mercury, MAC / biota (µg/kg)0,07 / 20 [6]0.07 / 20 in fish
Nickel, AA inland / AA other / MAC4 / 8,6 / 34 [10]4 (bioavailable) / 8.6 / 34
Lead, AA inland / AA other / MAC1,2 / 1,3 / 14 [15]1.2 (bioavailable) / 1.3 / 14
PFOS, AA inland / MAC inland / biota6,5 × 10⁻⁴ / 36 / 9,1 [7]0.00065 / 36 / 9.1 in fish
Cypermethrin, AA inland / AA other8 × 10⁻⁵ / 8 × 10⁻⁶ [12]0.00008 / 8 × 10⁻⁶
Terbutryn, AA inland / AA other0,065 / 0,0065 [16]0.0625 / 0.0065

One small difference: terbutryn's inland AA is 0.0625 in the EA freshwater list but 0,065 in the EU table.

From 22 December 2027: where they split

1. Tighter EU limits for existing substances. England keeps the 2013 values; the new EU values are from the Council text of Directive 2026/805 (PE-CONS 18/26, pp. 173-187):

  • Chlorpyrifos, AA inland: 0.03 in England, 4,6 × 10⁻⁴ in the EU.
  • Diuron, AA / MAC: 0.2 / 1.8 in England, 0,049 / 0,27 in the EU.
  • Mercury, biota: 20 µg/kg in England, 11 µg/kg in the EU.
  • Nickel, AA / MAC: 4 / 34 in England, 2 / 8,2 in the EU.
  • Fluoranthene, biota: 30 µg/kg in England, 6,1 µg/kg in the EU.
  • Cypermethrin, AA inland: 0.00008 in England, 3 × 10⁻⁵ in the EU.

2. New EU priority substances with no EA standard at all. The EA freshwater list has no entry for:

  • the hormones EE2, E2 and estrone;
  • azithromycin, carbamazepine, clarithromycin, diclofenac, erythromycin and ibuprofen;
  • the five neonicotinoids;
  • bifenthrin, deltamethrin and esfenvalerate;
  • nicosulfuron and bisphenol A;
  • the PFAS sum of 25 and the EU sum-of-pesticides value of 0,2 µg/l.

For PFAS, England still regulates only PFOS, at 0.00065 µg/l. The EU will apply a 25-PFAS sum: 0,0044 µg/l as PFOA-equivalents in water and 0,077 µg/kg in biota.

3. Substances the EU adds that England already covers with a weaker national standard. These are UK specific pollutants or operational standards in England, not priority substances:

Substance (AA inland, µg/l)England (EA)EU from 2027 (PE-CONS 18/26)
Glyphosate196 (MAC 398, 95th percentile)0,1 in drinking-water sources; 86,7 in other freshwater
Triclosan0.1 (MAC 0.28)0,02
Permethrin0.0012,7 × 10⁻⁴
Silver (dissolved)0.05 (operational standard)0,01

4. Substances the EU drops from the priority list. The EU moves alachlor, atrazine, carbon tetrachloride, chlorfenvinphos, simazine and trichlorobenzenes into Annex II Part C without changing their values. England still lists most of them as priority substances; carbon tetrachloride is already listed as "other pollutant". Atrazine is 0.6 / 2 in both regimes, so this changes their status, not the limits.

Other structural differences

  • Wider national lists in England. The EA tables mix priority substances with UK specific pollutants and operational standards that have no EU-level equivalent. Examples are copper at 1 µg/l (bioavailable), zinc at 10.9 µg/l (bioavailable, plus background), manganese at 123 µg/l (bioavailable) and iron at 1000 µg/l. Many of these short-term limits are written as 95th-percentile values, which the EU's MAC-EQS are not.
  • No UK counterpart found for the other new EU obligations. I found nothing in the UK sources I opened matching the EU's harmonised repository of national-pollutant EQS (Annex II Part C), its effect-based estrogen monitoring from 2030, or the 2027 to 2039 compliance timetable.

Sources:

Q.03