What's really in our water? We can't manage what we can't measure

Irish Examiner

25-04-2025

Ireland's waters are in trouble — and not just from the usual suspects. Sure, fertiliser runoff still feeds algal blooms in streams and lakes. But there's more to the story: salmon swimming on anxiety medication, pesticides disrupting aquatic food chains, and forever chemicals that refuse to break down. You could say our lakes, rivers, and wetlands have become chemical cocktails — shaken, stirred, and dangerously under-regulated.
This isn't some distant, invisible threat. It's flowing beneath our bridges, past our farms and towns, and into our drinking water supplies. And while new data shows glimmers of improvement, our freshwater systems are under pressure like never before, caught between climate extremes, land-use change, and the leftover chemistry of modern life.
The question isn't whether our waters can recover. It's whether we're willing to help them.
From fertiliser to pharma
Farming has long shaped Ireland's landscape. But when fertilisers and slurry run off into lakes, rivers, and streams, they tip the ecological balance. Nitrates and phosphates (usual suspects) feed harmful algal blooms, strip oxygen from the water, and stress fish and invertebrates. According to the EPA, 40% of freshwater monitoring sites were impacted by nutrient pollution in 2023, with knock-on effects for biodiversity, water quality, and industries like fishing and tourism. But there's hope. In 2024, nitrate levels in Irish freshwaters dropped to their lowest in nearly a decade, thanks to smarter fertiliser use, tighter regulations, and growing investment in sustainable practices. It shows that change is possible and already happening.
The researchers Daniel Cerveny and Marcus Michelangeli from SLU in Umeå are collecting juvenile salmon in the Dal River. The juvenile salmon formed the foundation of the study published in Science. Image:Michael Bertram
At the same time, another issue has quietly re-surfaced: pharmaceutical pollution. A 2025 Science study found that Atlantic salmon exposed to clobazam (an anti-anxiety drug found in wastewater) behaved very differently. They navigated migration routes faster and bypassed hydropower barriers more successfully. But they also abandoned their usual group behaviours, ignored predator cues, and showed signs of risky behaviour. Speedy, but less safe.
If trace amounts of medication can change how salmon behave, what impact are they having on frogs in ponds, daphnia in lakes, or mayflies in headwater streams?
Chemical cocktails and murky waters
Clobazam is just one ingredient. Ireland's water bodies also carry residues of painkillers, antibiotics, antihistamines, and synthetic hormones. PFAS (the forever chemicals used in waterproof clothing, cookware, and firefighting foam) persist in freshwater ecosystems and accumulate in animals and humans. Pesticides alter hormone systems in fish and amphibians. Microplastics drift through lakes and wetlands, offering sticky surfaces for pollutants and microbes to hitch a ride.
Unlike nutrients, these pollutants are harder to track. While some water quality parameters can be monitored with sensors, detecting pharmaceuticals, PFAS, and microplastics still requires advanced lab testing — something Ireland currently does on a limited scale.
Michael Bertram: Our study is among the first to show that pharmaceutical pollution can affect not just behaviour in the lab, but outcomes for animals in their natural environment. Bertram is an assistant professor in Ecology and Ecotoxicology at the Swedish University of Agricultural Sciences
Carbon in water
Another concern that often goes overlooked is Dissolved Organic Carbon (DOC) — a mix of organic molecules leached from soils, vegetation, and especially peatlands. DOC naturally occurs in bog-fed waters, giving them their familiar tea-coloured hue. But levels are rising globally, driven by changes in land use, peatland drainage, and climate-induced shifts in rainfall and runoff. While elevated DOC isn't necessarily toxic, but it can have indirect impacts. It can alter light penetration in lakes and streams, affecting photosynthesis and potentially aquatic food webs. It can bind with metals and pollutants, changing their mobility.
And in drinking water treatment, high DOC can increase the formation of harmful disinfection byproducts when it reacts with chlorine.
Despite its growing importance, DOC remains poorly monitored across Ireland. It's a blind spot in water quality management. One we urgently need to fix, especially as peatlands are disturbed and rainfall patterns shift with climate change.
Treatment tech: playing catch-up
Most of Ireland's water treatment plants were designed to tackle yesterday's threats — bacteria and basic pollutants — not today's chemical soups. Nitrates often pass through. PFAS defy most filters. Even chlorine, our go-to disinfectant, can backfire when it reacts with DOC to produce harmful compounds. Solutions exist, from activated carbon to advanced oxidation and membrane filtration. But retrofitting treatment plants is expensive, logistically challenging, especially for rural or older infrastructure.
A national rescue mission
So, what's the fix? It starts upstream. Support farmers who reduce fertiliser use and restore buffer zones along waterways. Incentivise peatland restoration and more native tree planting to soak up runoff before it enters the system. Invest in treatment technologies that can remove more than just the basics. And develop a national framework to track and regulate pharmaceutical and chemical pollutants across all freshwater environments.
Equally important is public awareness. Most people don't realise that drugs that we consume and excrete can end up in the nearest stream. Protecting water quality requires buy-in from communities, councils, hospitals, households, and industries alike.
It also means improving our science. Testing for pharmaceuticals, PFAS, DOC, or emerging contaminants should be part of routine water monitoring — not an occasional research project. Without data, we can't manage what we can't measure.
Blue future
Water is fundamental. It flows through every part of life, shaping landscapes, fuelling agriculture, sustaining ecosystems, and underpinning public health. Yet in Ireland, clean water is often taken for granted, as if it's an infinite, self-cleaning resource.
But that illusion is wearing thin. Our freshwater systems are absorbing the costs of modern life, from overuse of fertilisers and pharmaceuticals to a lack of planning for climate-driven extremes. These aren't just environmental issues. They're economic, public health, and social ones too. Clean water is central to our economy, not just our ecology. But we can't protect what we don't prioritise. Water must be recognised not just as a utility, but as a national asset that underpins everything else. Here's to clean water — raises glass.