Understanding the invisible chemical invaders threatening our global water resources
Imagine a chemical so persistent that it refuses to break down, so mobile that it travels unchecked through our ecosystems, and so toxic that it threatens human health and environmental stability.
This isn't science fiction—it's the reality of PMT (persistent, mobile, and toxic) and vPvM (very persistent and very mobile) substances that are quietly spreading through our planet's water resources 7 . For decades, regulators and scientists have focused on chemicals that accumulate in living organisms, but now a new class of equally concerning substances has emerged—those that accumulate not in flesh, but in water systems, bypassing traditional filtration systems and posing unique challenges for detection and removal 7 .
The European Chemicals Agency (ECHA) has officially recognized these substances as posing an equivalent level of concern to their better-known cousins—PBT (persistent, bioaccumulative, and toxic) and vPvB (very persistent and very bioaccumulative) substances 7 . This article explores how this recognition came to be, the scientific evidence behind it, and what it means for our future environmental safety.
PMT substances accumulate in water resources rather than biological tissues
Traditional water treatment systems struggle to remove these mobile chemicals
Examples include brominated flame retardants and industrial chemicals like PIP 3:1 8
| Property | PBT/vPvB Substances | PMT/vPvM Substances |
|---|---|---|
| Primary Concern | Bioaccumulation in food chains | Contamination of water resources |
| Environmental Pathway | Biological tissues, fat | Water systems, groundwater |
| Detection Priority | Living organisms | Drinking water sources |
| Removal Challenge | Food chain magnification | Water treatment inefficiency |
| Regulatory History | Longer recognition and management | Emerging recognition (EU CLP 2023) |
PBT: Bioaccumulation Pathway
PMT: Water Contamination Pathway
The European Union took a groundbreaking step in 2023 by formally adopting new hazard classes under its Classification, Labelling and Packaging (CLP) Regulation, explicitly grouping PBT/vPvB and PMT/vPvM substances together as equivalent concerns 1 6 . This regulatory change, implemented through Delegated Regulation (EU) 2023/707, represents a significant shift in how chemical hazards are evaluated and managed 1 9 .
Determine degradation half-life using OECD tests
Measure adsorption potential (log Koc value)
Evaluate harmful effects on aquatic organisms
Weight-of-evidence approach for final classification
| Substance | Persistence | Mobility (log Koc) | Toxicity | Water Treatment Removal |
|---|---|---|---|---|
| 1,4-dioxane | High (vP) | High (vM) | Likely carcinogen | Low efficiency 7 |
| Melamine | High (vP) | High (vM) | Bladder stones, carcinogen | Low efficiency 7 |
| GenX | High (vP) | High (vM) | Health concerns | Low efficiency 7 |
| PFBS | High (vP) | High (vM) | Health concerns | Low efficiency 7 |
Gather water samples from various sources across multiple locations
Measure degradation rates with natural microbial communities
Evaluate movement through soil types using column tests
Test on multiple trophic levels following OECD guidelines
Examine removal efficiency in simulated water treatment
Computational tools that predict substance properties based on structural similarities 7
Use data from similar substances to fill information gaps 7
Standardized laboratory protocols for determining chemical properties 7
HPLC-MS enables detection at trace concentrations 7
Non-animal testing methods including in vitro assays and computational models that can provide data on endocrine disruption and other toxicity endpoints 5
With an estimated 28% of REACH-registered substances potentially meeting PMT/vPvM criteria (up to 3,677 substances), the scale of the challenge is significant 7 . This recognition triggers several important developments:
Expanded programs to track PMT/vPvM substances in drinking water sources 7
Implementation of advanced oxidation processes and reverse osmosis 7
Managing entire classes of substances to prevent regrettable substitution 7
Manufacturers must assess substances and potentially reformulate products 2
The formal recognition that PMT/vPvM substances pose an equivalent level of concern to PBT/vPvB substances represents a significant evolution in how we evaluate chemical threats. This shift acknowledges that environmental persistence combined with either bioaccumulation potential or environmental mobility creates unacceptable long-term risks, regardless of the specific exposure pathway.