PFAS in Cergy's tap water: under 4 ng/L, none of the four main PFAS detected
Last PFAS check: · Source: Hub'eau
PFAS in drinking water
None of the 4 most harmful PFAS detected
The lab sees nothing below 4 ng/L, 8 times our benchmark of 0.5 ng/L. Water above our benchmark would pass this check unnoticed.
0.5 ng/L is our benchmark, not an official limit. Same EFSA method as Sweden, Denmark and the Netherlands, but stricter. It's a yearly average, compared here with the latest check.
Sample taken in Méry-sur-Oise, on the same distribution network as Cergy (CACP CERGY-ST CHRIST PUISEUX PONTOISE). The health authority samples one tap per network; a network carries the same treated water everywhere.
More about this result
The US also limits PFOA and PFOS to 4 ng/L each, per substance.
The lab detects each of the four substances from 1 ng/L upward. None reached that limit, so their total is below 4 ng/L rather than zero.
checked on 25 March 2026
20 PFAS (see each substance)
| PFAS substance | Value |
|---|---|
| Acide perfluoropentanoïque (PFPEA) | 0.001 µg/L |
| Acide perfluorododécanoique (PFDoDA) | <0,001 µg/L |
| Acide sulfonique de perfluorooctane (PFOS) | <0,001 µg/L |
| Acide sulfonique de perfluorobutane (PFBS) | <0,001 µg/L |
| Acide perfluoro-octanoïque (PFOA) | <0,0010 µg/L |
| Acide perfluoro tridecane sulfonique (PFTrDS) | <0,005 µg/L |
| Acide perfluorohexanoïque (PFHXA) | <0,002 µg/L |
| Acide perfluorodecane sulfonique (PFDS) | <0,001 µg/L |
| Acide perfluoro-decanoïque (PFDA) | <0,001 µg/L |
| Acide perfluorobutanoïque (PFBA) | <0,002 µg/L |
| Acide perfluoro undecane sulfonique (PFUnDS) | <0,002 µg/L |
| Acide perfluoroheptanoïque (PFHPA) | <0,001 µg/L |
| Acide perfluoro-nonanoïque (PFNA) | <0,001 µg/L |
| Acide perfluorononane sulfonique (PFNS) | <0,002 µg/L |
| Acide perfluorododécane sulfonique (PFDoDS) | <0,001 µg/L |
| Perfluorohexane sulfonate (PFHXS) | <0,001 µg/L |
| Acide perfluoroheptane sulfonique (PFHpS) | <0,002 µg/L |
| Acide perfluoro undecanoïque (PFUnA) | <0,001 µg/L |
| Acide perfluoro tridecanoique (PFTrDA) | <0,001 µg/L |
| Acide perfluoropentane sulfonique (PFPS) | <0,001 µg/L |
Fails a current legal limit. The details are below.
Water report for Cergy
Get new PFAS results for Cergy, with a short explanation. At most one update a week, only when there's something new.
- EU legal limit
- 1 ng/L sum of 20 PFAS, below the 100 ng/L limit
- Last PFAS test
- 25 March 2026
- Water supplier
- CYO'
In Cergy, none of the 4 most closely watched PFAS (PFAS-4) was detected at the latest PFAS check on 25 March 2026. The total is below 4 ng/L, the sum of the detection limits and 8 times our 0.5 ng/L benchmark. Sum of 20 PFAS: 1 ng/L (0.001 µg/L), below the EU legal limit (100 ng/L). Sampled in Méry-sur-Oise, on the same network. 40 checks since 24 January 2025: sum of 20 PFAS up to 39 ng/L, sometimes below the detection limit. Source: Hub'eau, Qualité de l'eau potable (Ministère de la Santé / OFB / BRGM).
Details and sources
PFAS over time in Cergy
40 PFAS checks since 24 January 2025, from the published measurements. Samples from 7 communes on the same network: it's the same water, so each one applies to Cergy. Samples come from 4 distribution networks. The trend refers to the network “CACP CERGY-ST CHRIST PUISEUX PONTOISE”.
“Calculated”: PFAS-4 worked out from the four substances in the same sample. The chart, averages and trends use lab-published sums only.
| Date | PFAS-4 | Sum of 20 PFAS | Sampled at | Network |
|---|---|---|---|---|
| < 4 ng/L · calculated | 1 ng/L | Méry-sur-Oise | CACP CERGY-ST CHRIST PUISEUX PONTOISE, CACP NORD | |
| < 4 ng/L · calculated | < 29 ng/L | Courdimanche | CACP OUEST | |
| < 4 ng/L · calculated | < 29 ng/L | Méry-sur-Oise | CACP CERGY-ST CHRIST PUISEUX PONTOISE, CACP NORD | |
| < 4 ng/L · calculated | 3 ng/L | Méry-sur-Oise | CACP CERGY-ST CHRIST PUISEUX PONTOISE, CACP NORD | |
| 12 ng/L – < 13 ng/L · calculated | 23 ng/L | Boisemont | CACP OUEST | |
| < 4 ng/L · calculated | 2 ng/L | Cergy | CACP NORD | |
| 6 ng/L – < 7 ng/L · calculated | 18 ng/L | Vauréal | CACP PREFECTURE VILLAGES | |
| < 4 ng/L · calculated | < 29 ng/L | Méry-sur-Oise | CACP CERGY-ST CHRIST PUISEUX PONTOISE, CACP NORD | |
| < 4 ng/L · calculated | < 29 ng/L | Menucourt | CACP OUEST | |
| < 4 ng/L · calculated | < 29 ng/L | Méry-sur-Oise | CACP CERGY-ST CHRIST PUISEUX PONTOISE, CACP NORD | |
| 1 ng/L – < 4 ng/L · calculated | 10 ng/L | Méry-sur-Oise | CACP CERGY-ST CHRIST PUISEUX PONTOISE, CACP NORD | |
| 15 ng/L – < 16 ng/L · calculated | 30 ng/L | Courdimanche | CACP CERGY-ST CHRIST PUISEUX PONTOISE |
Show the 28 earlier checks (back to 24 January 2025)
| 4 ng/L – < 6 ng/L · calculated | 15 ng/L | Cergy | CACP PREFECTURE VILLAGES | |
| < 4 ng/L · calculated | 2 ng/L | Méry-sur-Oise | CACP CERGY-ST CHRIST PUISEUX PONTOISE, CACP NORD | |
| 2 ng/L – < 4 ng/L · calculated | 3 ng/L | Boisemont | CACP OUEST | |
| < 4 ng/L · calculated | < 29 ng/L | Menucourt | CACP OUEST | |
| 11 ng/L – < 12 ng/L · calculated | 23 ng/L | Osny | CACP NORD | |
| < 4 ng/L · calculated | 6 ng/L | Osny | CACP CERGY-ST CHRIST PUISEUX PONTOISE, CACP NORD +1 | |
| < 4 ng/L · calculated | 3 ng/L | Méry-sur-Oise | CACP CERGY-ST CHRIST PUISEUX PONTOISE, CACP NORD | |
| 2 ng/L – < 4 ng/L · calculated | 10 ng/L | Osny | CACP CERGY-ST CHRIST PUISEUX PONTOISE, CACP NORD +1 | |
| 1 ng/L – < 4 ng/L · calculated | 9 ng/L | Méry-sur-Oise | CACP CERGY-ST CHRIST PUISEUX PONTOISE, CACP NORD | |
| 20 ng/L – < 21 ng/L · calculated | 38 ng/L | Courdimanche | CACP CERGY-ST CHRIST PUISEUX PONTOISE | |
| 1 ng/L – < 4 ng/L · calculated | 6 ng/L | Méry-sur-Oise | CACP CERGY-ST CHRIST PUISEUX PONTOISE, CACP NORD | |
| < 4 ng/L · calculated | 3 ng/L | Méry-sur-Oise | CACP CERGY-ST CHRIST PUISEUX PONTOISE, CACP NORD | |
| 6 ng/L – < 7 ng/L · calculated | 16 ng/L | Cergy | CACP PREFECTURE VILLAGES | |
| 1 ng/L – < 4 ng/L · calculated | 10 ng/L | Méry-sur-Oise | CACP CERGY-ST CHRIST PUISEUX PONTOISE, CACP NORD | |
| 17 ng/L – < 18 ng/L · calculated | 31 ng/L | Osny | CACP NORD | |
| < 4 ng/L · calculated | 2 ng/L | Menucourt | CACP OUEST | |
| < 4 ng/L · calculated | 5 ng/L | Boisemont | CACP OUEST | |
| < 4 ng/L · calculated | 4 ng/L | Méry-sur-Oise | CACP CERGY-ST CHRIST PUISEUX PONTOISE, CACP NORD | |
| < 4 ng/L · calculated | 4 ng/L | Osny | CACP CERGY-ST CHRIST PUISEUX PONTOISE, CACP NORD +1 | |
| 19 ng/L – < 20 ng/L · calculated | 39 ng/L | Courdimanche | CACP CERGY-ST CHRIST PUISEUX PONTOISE | |
| < 4 ng/L · calculated | 7 ng/L | Méry-sur-Oise | CACP CERGY-ST CHRIST PUISEUX PONTOISE, CACP NORD | |
| < 4 ng/L · calculated | 2 ng/L | Méry-sur-Oise | CACP CERGY-ST CHRIST PUISEUX PONTOISE, CACP NORD | |
| 18 ng/L – < 19 ng/L · calculated | 37 ng/L | Osny | CACP NORD | |
| < 4 ng/L · calculated | 8 ng/L | Boisemont | CACP OUEST | |
| 1 ng/L – < 4 ng/L · calculated | 16 ng/L | Courdimanche | CACP CERGY-ST CHRIST PUISEUX PONTOISE | |
| 6 ng/L – < 7 ng/L · calculated | 19 ng/L | Cergy | CACP PREFECTURE VILLAGES | |
| < 4 ng/L · calculated | 1 ng/L | Méry-sur-Oise | CACP CERGY-ST CHRIST PUISEUX PONTOISE, CACP NORD | |
| < 4 ng/L · calculated | < 1 ng/L | Méry-sur-Oise | CACP CERGY-ST CHRIST PUISEUX PONTOISE, CACP NORD |
Calculated values: “<” is an upper bound from published thresholds, “≥” a lower bound, “–” means no published sum or complete measurement. How to read a PFAS result
What the latest check found
At the latest check, the water was within every limit tested.
Values to watch
These results are close to their legal limit, or over it.
| What was tested | Value | Limit | Status |
|---|---|---|---|
| Nitrate | 27 mg/L | ≤ 50 mg/L | within the limit |
| Lead | 12 µg/L | ≤ 10 µg/L | over the limit |
See all 21 test results
| What was tested | Value | Limit | Status |
|---|---|---|---|
| Nitrate | 27 mg/L | ≤ 50 mg/L | within the limit |
| Nitrite | <0,01 mg/L | ≤ 0.5 mg/L | within the limit |
| Lead | 12 µg/L | ≤ 10 µg/L | over the limit |
| Copper | 0.222 mg(Cu)/L | ≤ 2 mg(Cu)/L | within the limit |
| Nickel | 8 µg/L | ≤ 20 µg/L | within the limit |
| Arsenic | <2 µg/L | ≤ 10 µg/L | within the limit |
| Cadmium | <1 µg/L | ≤ 5 µg/L | within the limit |
| Chromium | <5,00 µg/L | ≤ 50 µg/L | within the limit |
| Uranium | <10 µg/L | ≤ 30 µg/L | within the limit |
| Fluoride | 0.11 mg/L | ≤ 1.5 mg/L | within the limit |
| Escherichia coli | 0 n/(100mL) | ≤ 0 mL) | within the limit |
| Enterococci | 0 n/(100mL) | ≤ 0 mL) | within the limit |
| Coliform bacteria | 0 n/(100mL) | ≤ 0 mL) | within the limit |
| pH | 7.2 unité pH | 6.5–9 unité pH | within the limit |
| Water hardness | 29.38 °f | no limit | for reference |
| Electrical conductivity | 772 µS/cm | 200–1,100 µS/cm | within the limit |
| Chloride | 47.8 mg/L | ≤ 250 mg/L | within the limit |
| Sulphate | 26.9 mg/L | ≤ 250 mg/L | within the limit |
| Sodium | 17 mg/L | ≤ 200 mg/L | within the limit |
| Iron | <10 µg/L | ≤ 200 µg/L | within the limit |
| Turbidity | <0,1 NFU | ≤ 2 NFU | within the limit |
Frequently asked questions
Is tap water in Cergy safe to drink?
At the latest check, the water was over at least one limit. “Eau d'alimentation conforme aux exigences de qualité en vigueur pour l'ensemble des paramètres mesurés.”
How high are PFAS levels in Cergy's drinking water?
The total of 20 PFAS ("forever chemicals") was last measured at 1 ng/L. The EU limit is 100 ng/L, so this water is at 1 % of the limit. (below the EU limit)
Does the water in Cergy also meet the strictest limits in Europe?
As far as this check can tell, yes. None of the four compounds was quantified, so their total is below 4 ng/L, the sum of the laboratory's detection limits, and under Sweden's legal limit of 4 ng/L in force since 2026.
Are PFAS levels rising in Cergy's tap water?
Calculated PFAS-4 values are listed in the table. The chart uses laboratory-published sum-of-20 results; there are too few laboratory-published PFAS-4 sums for the existing trend calculation.
How hard is the water in Cergy?
The water hardness in Cergy is 29.4 °f (medium). This mainly matters for household appliances and detergent dosing, not for health.
Where does this data come from?
All values come from official publications: Hub'eau, Qualité de l'eau potable (Ministère de la Santé / OFB / BRGM). Retrieved on 21 September 2026.
Same water network
Same distribution network as Cergy, so in principle the same water.
Nearby communes
The closest to Cergy on this site.
Data source
- Hub'eau, Qualité de l'eau potable (Ministère de la Santé / OFB / BRGM)
- https://hubeau.eaufrance.fr/api/v1/qualite_eau_potable/resultats_dis?code_commune=95127
- License
- Licence Ouverte / Open Licence (Etalab)
- Retrieved
- 21 September 2026
- Supply networks
- CACP OUEST, CACP CERGY-ST CHRIST PUISEUX PONTOISE, CACP NORD, CACP PREFECTURE VILLAGES
This site is a data project, not an official source. If in doubt, check with your water supplier or local authority.