Few things say summer like a cool dip on a hot afternoon. Yet behind that inviting blue surface, swimming pool health risks are real and surprisingly under-discussed. Even a pool that looks crystal clear, smells "freshly chlorinated" and is topped up with the right chemicals can still expose swimmers to irritants and microbes that traditional treatment struggles to remove. In this guide, we look honestly at what the evidence does and does not say about the health risks of swimming pools, why that distinctive chlorine smell is actually a warning sign rather than a badge of cleanliness, and how modern UV-based water treatment can dramatically reduce the problem without drowning your water in chemicals.
Main takeaways if you're short on time
- Clear water isn't proof of clean water. The most relevant swimming pool health risks — trichloramine, resistant parasites and algal toxins — are invisible to the naked eye.
- That "chlorine smell" is trichloramine. It forms when chlorine reacts with sweat, skin and urine, and it irritates the eyes and airways rather than signalling a well-kept pool.
- Some parasites shrug off chlorine. Cryptosporidium and Giardia are notably chlorine-tolerant and are a documented cause of pool-related stomach upsets.
- More chlorine is not a healthier answer. Pushing chlorine levels up to fight algae increases disinfection by-products, so the goal is smarter treatment, not stronger dosing.
- UV and nanotechnology reduce the risks. Medium-pressure UV systems break down trichloramine and tackle resistant microbes, letting you keep chlorine to a sensible minimum.
Until fairly recently, removing certain health-relevant substances from pool water was simply beyond the reach of home equipment. Public pools and wellness centres had the technology; private pool owners did not. That has changed. Modern medium-pressure UV systems such as the ProfiPure UVM can break down trichloramine and help control parasites and algae, bringing the kind of water quality once reserved for Olympic-grade facilities within reach of an ordinary garden pool. Before we get to the solution, though, it is worth understanding exactly what we are dealing with.
Where the swimming pool health risks start: contamination you can't see
No matter how carefully you maintain a pool, contaminants find their way in. Wind blows in dust, pollen and leaves; rain washes in whatever sits on the surroundings; and the biggest source of all walks in on two legs. The moment a swimmer enters the water, a remarkable quantity of organic material enters with them.
"But we always shower first," you might say. Showering helps — and it genuinely reduces the load — but it does not make you sterile. Your body continuously sheds microscopic skin cells, hair, sweat, sebum and mucus, along with traces of cosmetics and sun cream. Add the bacteria, viruses, fungi and yeasts that everyone carries, and a busy pool is constantly being fed with organic matter. On their own, these substances degrade water quality. More importantly, they are the raw material from which the real swimming pool health risks are manufactured.
This is where chemistry takes over. Chlorine is added to disinfect, and it does an essential job. The trouble is that chlorine does not simply kill germs and disappear — it reacts with all that organic material to create a cocktail of by-products. Some are harmless. A few are not.
Trichloramine: the irritant hiding in plain sight
When chlorine meets nitrogen-rich contaminants such as sweat and urine, it forms chloramines. Of these, trichloramine (also called nitrogen trichloride, a form of combined chlorine) is the one most consistently linked to discomfort and irritation among swimmers and pool staff. Because trichloramine is poorly soluble in water, it does not stay safely dissolved. It escapes from the surface and accumulates in the air directly above the water — exactly where you breathe.
The published research, particularly studies of indoor pool workers and competitive swimmers, associates trichloramine exposure with a range of effects:
- Stinging, red eyes and conjunctival irritation
- Coughing, throat irritation and a feeling of tightness in the chest
- Irritation of the lining of the upper airways
- Aggravation of symptoms in people who already have asthma
- Reactions in sensitive or allergy-prone individuals
- Dry, irritated skin
It is worth being precise here, because scare stories help nobody. The strongest evidence concerns irritation and the worsening of existing respiratory conditions, especially with heavy, repeated exposure in poorly ventilated indoor pools. Research has also explored whether high early-life exposure to chlorination by-products may contribute to airway sensitivity in some children, though scientists continue to debate how large that effect is. What is not in serious dispute is the everyday reality: that sharp "swimming pool smell" is not the smell of cleanliness, but of trichloramine — and the stronger it is, the more combined chlorine the water and air contain. If you want the full chemistry, our detailed article on what trichloramine is and why it matters goes deeper.
What about saltwater pools?
A persistent myth claims that saltwater pools are chlorine-free and therefore trichloramine-free. They are not. A saltwater pool simply makes its chlorine on site: an electrolytic cell splits dissolved salt (sodium chloride) to generate chlorine directly in the water. The end result is still chlorinated water, and when that chlorine meets the same sweat and skin, the same trichloramine can form. Saltwater systems have genuine advantages for comfort and convenience, but immunity from combined chlorine is not one of them.
Parasites: the danger that clear water can't reveal
Among the more underestimated health risks of swimming pools are waterborne parasites. Many people assume parasites belong to lakes and rivers, not to a tiled, chlorinated pool. Unfortunately, several of the most relevant ones are notably tolerant of chlorine at the levels normally used for disinfection.
Cryptosporidium and Giardia are the classic examples. Cryptosporidium, in particular, is protected by a tough outer shell that lets it survive in properly chlorinated water for days, which is why it is one of the most common causes of pool-linked illness internationally. If a swimmer swallows even a small amount of contaminated water, the result can be:
watery diarrhoea, vomiting, mild fever, stomach cramps, headaches, loss of appetite and persistent fatigue, sometimes lasting one to two weeks. For most healthy adults, it is a thoroughly unpleasant interlude. For young children, older people and anyone with a weakened immune system, it can be considerably more serious. The practical defences are sensible ones: don't swallow pool water, keep anyone with a stomach upset out of the pool for two weeks after symptoms stop, and choose treatment technology that actually tackles chlorine-resistant organisms rather than relying on chlorine alone.
Algae: more than an ugly green tint
Nothing ruins the look of a pool faster than algae. Let water balance slip — too little circulation, too much sunlight, not enough disinfection — and pristine water can turn green almost overnight. Most owners treat this as a purely cosmetic nuisance, but overgrown algae can carry a subtler concern.
Certain types of algae, specifically cyanobacteria (often called blue-green algae), can release cyanotoxins. At the levels you might encounter in a neglected garden pool, these are far more likely to cause minor irritation — nausea, headaches or allergic-type skin reactions — than anything dramatic. Severe poisoning is associated mainly with heavy blooms in natural lakes and reservoirs, not typical private pools. Still, the message is simple: green water is a signal that your treatment is failing, and that signal is worth taking seriously.
Here lies the central dilemma of conventional pool care. Yes, higher chlorine concentrations suppress algae. But cranking up chlorine to keep water clear also means more disinfection by-products, including more trichloramine. You end up trading one swimming pool health risk for another. The way out is not more chemistry but better technology.
The smarter solution: less chlorine, cleaner water
This is exactly why public swimming pools, spas and wellness centres increasingly rely on medium-pressure ultraviolet (UV) systems. Rather than poisoning microbes with ever-higher chemical doses, UV light at the right wavelengths does two valuable jobs at once: it inactivates bacteria, viruses and even chlorine-tolerant parasites such as Cryptosporidium, and it photochemically breaks down trichloramine and other combined-chlorine compounds already present in the water. The benefit is recognised in the respected German standard DIN 19643 for pool water treatment.
The good news is that this professional-grade approach is no longer the exclusive preserve of municipal pools. Through LIFETECH's ProfiPure UVM range, the same medium-pressure UV technology can be fitted to a private pool. The result is water that stays genuinely cleaner with markedly less reliance on chlorine — which is precisely what reduces trichloramine in the air you breathe poolside, and with it one of the most stubborn swimming pool health risks.
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ProfiPure UVM
A medium-pressure UV system that destroys bacteria, viruses and microorganisms and actively breaks down trichloramine — the irritating combined chlorine behind that "pool smell". Its effectiveness aligns with the German DIN 19643 standard for pool water treatment.
View price →How to choose the right water treatment
The best setup depends on your pool, but the underlying principle is the same: combine effective disinfection with active removal of combined chlorine, so you can keep chemical dosing as low as is safely possible. The medium-pressure ProfiPure UVM goes well beyond simple disinfection. By reliably knocking out bacteria, viruses and other microbes while simultaneously breaking down trichloramine, it provides a stable, low-chemistry route to clean water throughout the swimming season — a meaningful answer to the most common swimming pool health risks.
If you would rather reduce chemistry from a completely different angle, there is a second option worth knowing about. The FN NANO® AQUA environment-friendly pool cleaner uses a photocatalytic nanocoating: under daylight, the treated surfaces help break down organic contamination and inhibit the regrowth of algae and biofilm. It is a gentler, lower-chemical way to keep water and pool walls clean, and it pairs naturally with reduced chlorine dosing. Many owners use the two approaches together — UV for the water column, photocatalysis for the surfaces.
Lower-chemistry pool care
Whichever route you take, the principle holds: the aim is not to swim in stronger chemicals, but to swim in genuinely cleaner water. Pair the right disinfection with a way of actively removing combined chlorine, and you address the eye-stinging, throat-tickling reality that most swimmers simply put up with.
Tip: How to clean a pool without harsh chemicals walks through practical, low-chemical maintenance step by step. And when summer ends, getting your pool ready for winter the gentle way protects both the water and your equipment for next year.
Conclusion: clear water deserves a closer look
It is tempting to judge a pool by its sparkle, but the genuine swimming pool health risks never announce themselves visually — the ones that matter are precisely the ones you cannot see, and no amount of clarity will reveal them. Trichloramine drifts invisibly above the surface, chlorine-resistant parasites survive in water that looks immaculate, and algae release their toxins quietly before the green tint even appears. None of this means you should be afraid of swimming — it is one of the healthiest activities there is. It simply means that "looks clean" and "smells of chlorine" are the wrong tests. The right test is how the water is treated. By cutting your reliance on chlorine and adding technology that actively removes combined chlorine and resistant microbes, you can keep all the joy of swimming and leave most of the risk behind.
Frequently asked questions
What are the main health risks of swimming pools?
The most relevant swimming pool health risks come from water contamination and the by-products of disinfection rather than from swimming itself. The main ones are trichloramine (a combined-chlorine irritant that affects the eyes and airways), chlorine-tolerant parasites such as Cryptosporidium and Giardia, and toxins released by overgrown algae. Good ventilation, sensible hygiene and modern water treatment greatly reduce all of them.
Is the strong chlorine smell at a pool a good sign?
No — it is the opposite. A clean, well-treated pool has almost no smell. That sharp "chlorine" odour is actually trichloramine, a combined-chlorine compound formed when chlorine reacts with sweat, skin and urine. The stronger the smell, the more combined chlorine is present, which is why it tends to irritate the eyes and throat.
Can you catch an infection from pool water even if it looks clean?
Yes. Clear water is not the same as germ-free water. Parasites such as Cryptosporidium are highly tolerant of chlorine and can survive in water that looks perfectly clean. Swallowing even a small amount of contaminated water can cause diarrhoea and stomach upset, so the simplest precaution is to avoid swallowing pool water and to keep anyone with a stomach bug out of the pool.
Are saltwater pools free of chlorine and trichloramine?
No. A saltwater pool generates its own chlorine by electrolysing dissolved salt, so the water is still chlorinated. When that chlorine reacts with organic contaminants, the same trichloramine can form. Saltwater systems are often gentler on the skin and easier to manage, but they are not chlorine-free.
How can I reduce swimming pool health risks at home?
Shower before swimming, keep good water circulation, and don't try to solve every problem by simply adding more chlorine. The most effective step is to combine sound disinfection with technology that actively removes combined chlorine — for example, a medium-pressure UV system such as the ProfiPure UVM, optionally paired with a photocatalytic cleaner like FN NANO® AQUA — so you can keep chemical dosing to a safe minimum.
