Thirty nanograms per litre. That is the number most people remember from Health Canada’s PFAS objective for drinking water.
For a lab, the number is the easy part. The objective is a sum, and the rules for building that sum decide what the result means. One of those rules has a consequence that I think surprises people: the more sensitive the lab, the higher the sum it can report for the same water.
This piece is about what the objective asks the lab to measure. Compliance decisions belong to the water system and the province.
What the objective says
Health Canada published the objective on 9 August 2024 (Objective for Canadian drinking water quality: PFAS). The core of it (p. 2):
- 30 ng/L for the sum of 25 specified PFAS
- a result of non-detect counts as zero in the sum
- PFAS levels should be kept as low as reasonably achievable
It is an objective, set with the provinces and territories while a full guideline is developed, and it replaces the earlier PFOA and PFOS guidelines (pp. 1, 3). Enforcement is provincial.
The 25 compounds are exactly the analyte list of US EPA Method 533: the perfluorinated carboxylic and sulfonic acids from C4 to C12, three fluorotelomer sulfonates, and ether acids including HFPO-DA (GenX), ADONA and the chlorinated ether sulfonates (p. 2 and Appendix A).
One more fact about where the number comes from. Health Canada says a traditional health-based approach “was not adopted”, partly because the science is changing and there is no consensus on the most sensitive health effect (p. 26). The value was set as reasonably achievable by treatment, considering treatment data and analytical capability. It is a target for reducing exposure.
How the sum is built
This is the paragraph that matters most to a lab (p. 23):
The sum is calculated by adding the concentrations of each of the PFAS detected at or above the MRL established by the jurisdiction or the laboratory (whichever is lower).
MRL is the minimum reporting level. So for each of the 25 compounds:
- below the reporting limit: counts as zero
- at or above it: its concentration goes into the sum
- and the reporting limit used is the lower of the two: the jurisdiction’s or the lab’s own
Why a more sensitive lab can report a higher sum
Here is an illustration. The numbers are mine, chosen to show the arithmetic, and are not from any real sample.
Suppose a water contains 1.5 ng/L of each of the 25 PFAS. The true sum is 37.5 ng/L.
- Lab A reports down to 2 ng/L. Every compound is below its reporting limit, every one counts as zero, and the reported sum is 0 ng/L.
- Lab B reports down to 1 ng/L. Every compound is above its reporting limit, and the reported sum is 37.5 ng/L, above the objective.
Same water, opposite conclusions, and both labs followed the rule.
Real water does not have 25 compounds at the same level. Health Canada’s own Canadian data show a median sum of 2 ng/L in 463 Quebec tap waters sampled 2018–2021, with a maximum of 108 ng/L (p. 8). But the direction holds whenever several compounds sit between two labs’ reporting limits. A lab that lowers its reporting limits, or a utility that changes labs, can see its sum go up without any change in the water.
For anyone reading PFAS results, the practical step is simple: ask for the reporting limit of each of the 25 compounds with the result, and compare sums only when the reporting limits are the same.
Which method
Health Canada names a preference. Of the two methods EPA has approved for drinking water, it recommends Method 533, because it follows current best practice, including isotope dilution, and Method 537.1 does not (p. 14). 537.1 also does not cover the shortest-chain acids, PFBA and PFPeA (p. 15).
On sensitivity, it recommends that approved methods meet at least the UCMR5 minimum reporting levels, which range from 2 to 20 ng/L, and notes that “many laboratories can accurately report at 2 ng/L for most PFAS and 5 ng/L for the rest” (pp. 14–15).
Total organic fluorine and the TOP assay are described as useful screening tools, but not standardised and not a replacement for the 25-compound measurement (p. 16).
Canada, the EU and the US are three different kinds of limit
It is tempting to rank the three regions by their numbers. They measure different things.
| Limit | What it covers | |
|---|---|---|
| Canada (2024) | 30 ng/L | sum of 25 PFAS, including fluorotelomer sulfonates and ether acids |
| EU (from 12 January 2026) | 0.10 µg/L (100 ng/L) | sum of 20 PFAS acids |
| US (2024 rule) | 4.0 ng/L each | PFOA and PFOS individually |
Sources: Health Canada objective, p. 2; EU Directive 2020/2184, Annex I and Article 25; US EPA PFAS National Primary Drinking Water Regulation, 2024.
The lab requirements differ the same way. The EU guidelines turn the directive’s LOQ requirement into an average LOQ of 1.5 ng/L for each of the 20 compounds (EU technical guidelines, 2024, p. 6). The US rule counts results below the practical quantitation level as zero for compliance averaging.
The US rule is also moving. In May 2026 EPA proposed removing its limits for PFHxS, PFNA, HFPO-DA and the hazard index, and extending the PFOA and PFOS compliance date from 2029 to 2031, while keeping the 4.0 ng/L limits. When I checked on 2 October 2026, both were still proposals.
What this means for a lab
If your lab is setting up PFAS in drinking water for Canadian clients:
- Cover all 25 compounds. A method built for PFOA and PFOS alone does not answer the objective.
- Use isotope dilution, as Health Canada recommends.
- Report the reporting limit for each compound with every result, because the sum depends on it.
- Watch your blanks. At 1 to 2 ng/L per compound, background from tubing, caps and filters is a real part of the result. (I have written separately about syringe filters, where PTFE recovered only 61–80% of PFAS in one study.)
Sources
- Health Canada. Objective for Canadian drinking water quality: per- and polyfluoroalkyl substances. August 2024. Page numbers above are the printed page numbers.
- European Parliament and Council. Directive (EU) 2020/2184 on the quality of water intended for human consumption.
- European Commission. Technical guidelines regarding methods of analysis for monitoring of PFAS in water intended for human consumption, 2024.
- US EPA. PFAS National Primary Drinking Water Regulation, final rule, 2024; and the two proposed rules of May 2026 (rescission of four PFAS determinations; PFOA and PFOS compliance extension).
Limits and rules in this area change. Everything above was checked on 2 October 2026; check the current documents before you rely on a number.
If your lab is building or reviewing a PFAS method and the blanks or the reporting limits are the problem, tell me which on LinkedIn and I will tell you where I would start. The LC-MS troubleshooting cheatsheet covers the instrument side.
Common questions
- What is Health Canada's PFAS limit for drinking water?
- An objective of 30 ng/L for the sum of 25 specified PFAS, published in August 2024. It replaced the earlier guidelines for PFOA and PFOS. Health Canada also recommends keeping PFAS levels as low as reasonably achievable. It is an objective, with enforcement set by the provinces and territories.
- Which 25 PFAS are in the Canadian objective?
- The 25 PFAS measured by US EPA Method 533: perfluorinated carboxylic and sulfonic acids from C4 to C12, the 4:2, 6:2 and 8:2 fluorotelomer sulfonates, and ether acids such as HFPO-DA (GenX), ADONA and the chlorinated ether sulfonates.
- How are non-detects handled in the PFAS sum?
- A non-detect counts as zero. Each of the 25 PFAS detected at or above the reporting limit set by the jurisdiction or by the laboratory, whichever is lower, is added to the sum.
- Why can two labs report different PFAS sums for the same water?
- Because the sum includes every compound above the lab's own reporting limit when it is lower than the jurisdiction's. A lab that reports down to 1 ng/L adds compounds that a lab reporting at 2 ng/L counts as zero. With 25 compounds, those small amounts can add up to a different conclusion.
- Which analytical method does Health Canada recommend for PFAS in drinking water?
- EPA Method 533, because it uses isotope dilution, while EPA Method 537.1 does not. Health Canada also recommends methods that meet at least the UCMR5 minimum reporting levels of 2 to 20 ng/L, and notes many labs can report at 2 ng/L for most PFAS.
- How does Canada's PFAS limit compare with the EU and US?
- Canada: 30 ng/L for the sum of 25 PFAS. EU: 0.10 µg/L (100 ng/L) for the sum of 20 PFAS, applicable from 12 January 2026. US: 4.0 ng/L each for PFOA and PFOS; in May 2026 EPA proposed removing its limits for four other PFAS, which was still a proposal when this was written.