For most people, the smell of a chlorinated pool is simply the smell of summer. But for parents of kids in swim lessons, competitive athletes who train indoors year-round, or anyone who's noticed persistent coughing and congestion after time at the pool, the question comes up: is something in the water — or the air above it — affecting the lungs?

It's a reasonable question, and the science behind it is more nuanced than most pool-side conversations suggest. The short answer is that pool chemicals can affect respiratory health under certain conditions, but the mechanism is not what most people expect, and the risk varies substantially depending on exposure type, duration, and individual susceptibility.

The real culprit isn't chlorine itself

When people talk about "chlorine sensitivity" in pools, they're usually describing a reaction to chlorine itself. But the more accurately identified respiratory threat from pool environments isn't chlorine directly — it's a class of chemical byproducts that form when chlorine reacts with organic nitrogen compounds introduced by swimmers.

Every person who enters a pool brings with them sweat, urine, cosmetics, sunscreen, and other nitrogen-containing compounds. Chlorine reacts with these substances to produce disinfection byproducts, and the most significant of these for airborne respiratory exposure are chloramines, particularly trichloramine, also known as nitrogen trichloride. Chloramines form from the reaction of chlorine with nitrogen products including sweat, urine, dirt, and other wastes generated from swimmers using indoor pools or spas. 

Trichloramine is a volatile gas. It doesn't stay in the water — it releases into the air above the pool surface. Health problems of swimmers in indoor pools have traditionally been attributed to the chlorine in the water, but chlorine reacts with bodily proteins to form chloramines, with the most volatile and prevalent in the air above swimming pools being nitrogen trichloride. This distinction between chlorine in the water and chloramines in the air is central to understanding pool-related respiratory effects.

What the research shows about airway effects

The evidence for respiratory effects of pool chloramines is strongest and most consistent in occupational settings — that is, among people with the highest and most sustained exposure.

A study published in the European Respiratory Journal examined 624 pool workers across 38 swimming facilities and found that employees with higher trichloramine exposure reported upper respiratory symptoms with greater frequency, with statistically significant associations for hoarseness, lost voice, and sinusitis. General respiratory symptoms were significantly elevated compared to a Dutch population sample, and an excess risk for symptoms indicative of asthma was observed in swimming pool employees. 

The first documented series of workers who developed occupational asthma following exposure to airborne chloramines in indoor chlorinated swimming pools included two lifeguards and one swimming teacher. Air measurements in one of the pools showed nitrogen trichloride levels of 0.1 to 0.57 milligrams per cubic meter. 

For competitive swimmers, a similar pattern emerges at high cumulative exposures. Research published in Respiratory Research found that constant exposure to chlorine byproducts in covered pools could cause damage to the mucosa of the airways and increase nasal and lung permeability, contributing to various types of inflammation and remodelling of the airways of highly skilled swimmers. Studies of elite swimmers have reported high prevalences of bronchial hyperresponsiveness and chronic nasal symptoms, and the association between long-term exposure to a chlorinated swimming pool and elevated serum IgE levels suggests a possible link between chlorine exposure and the development of various pulmonary dysfunctions. 

The childhood asthma question is genuinely contested

A separate and more publicly debated question is whether childhood pool attendance increases the risk of developing asthma. This is where the evidence is most divided, and where precision matters most.

Several observational studies from European research groups, particularly from Belgian investigators led by Alfred Bernard, proposed a "pool chlorine hypothesis" — the idea that trichloramine exposure in early childhood may damage the epithelial lining of the airways, potentially facilitating allergen sensitization and increasing asthma risk. A study examining the prevalence of childhood asthma across Europe found associations between wheezing and ever-asthma and the availability of indoor chlorinated swimming pools, reinforcing calls to pursue research on the long-term respiratory effects of chlorination products that children inhale as gases or aerosols. 

However, a large prospective British cohort study — the ALSPAC cohort, which followed 5,738 children from birth to age ten — reached the opposite conclusion. The prospective study showed that attending swimming pools did not increase asthma risk in children, and appeared to be associated with better lung function and fewer respiratory symptoms, particularly in children with asthma

A systematic review and meta-analysis, published in 2016, examined seven studies encompassing over 5,800 subjects and similarly found that current evidence of an association between visits to indoor pools by babies and young children and new-onset asthma is suggestive but not conclusive, with shortcomings in current studies in the areas of exposure assessment, the age at time of exposure, and the characterization of asthma. 

The honest summary is that the question is not settled. Cross-sectional and ecological studies suggest a possible association; the one large-scale prospective study does not support it for recreational swimmers. Resolving the discrepancy requires better-designed studies with accurate individual exposure measurements, which most existing research has lacked.

Who carries the greatest risk

The evidence is considerably more consistent when it comes to specific populations. While occasional or low-level exposure to chlorine might not be harmful, regular swimmers, especially those at competitive levels, are at a higher risk of developing respiratory disorders. Lifeguards, swim instructors, and pool workers face the highest cumulative exposure and the most documented risk.

People with pre-existing asthma or exercise-induced bronchoconstriction represent another group that warrants careful attention. The warm, humid environment of a pool is often described as beneficial for people with asthma, and for many it is. But trichloramine in poorly ventilated indoor pools adds a chemical irritant load to the respiratory system at the same time as physical exertion increases respiratory demand. For individuals with already-reactive airways, that combination may provoke symptoms.

Atopy — the genetic tendency to develop allergic conditions — also appears to modify the relationship between pool exposure and airway outcomes. Cumulative pool attendance emerged among the most consistent predictors of asthma in one study, ranking immediately after atopy. Research suggests that trichloramine and other chlorine-based oxidants in indoor swimming pools may facilitate the passage of allergens across the epithelial barriers of the respiratory tract, potentially acting as a chemical adjuvant in the development of allergic sensitization. This is a proposed mechanism, not an established certainty, and it has not been confirmed in subsequent human studies.

Indoor versus outdoor, and ventilation as the key variable

One consistent finding across the research is that indoor pool environments carry substantially greater respiratory risk than outdoor pools, primarily because of ventilation differences. Trichloramine is heavier than air and accumulates just above the water surface, in the breathing zone of swimmers. In enclosed natatoriums, without adequate fresh air exchange, concentrations build over the course of a session as the number of bathers increases.

Chloramines can move readily into indoor air from pool or spa water as chloramine levels increase or as the bather load increases. Warm water temperatures or the amount of agitation from fountains, sprays, or slides also increases the amount of chloramines that affect indoor air at indoor pool and spa settings. Air recycling devices may concentrate chloramines as these devices recycle air to save on heating costs and provide less makeup air into the facility. 

Outdoor pools have substantially better natural dilution, which explains why even studies that find dose-dependent associations between pool attendance and respiratory outcomes tend to find stronger effects for indoor pool exposure.

Showering before entering the pool meaningfully reduces chloramine formation, because it removes the sweat and other nitrogen-containing compounds that chlorine would otherwise react with. Maintaining proper water chemistry and showering before using the pool or spa will greatly reduce the amount of chloramines in indoor air.  Pool management practices — maintaining appropriate free chlorine levels, monitoring combined chlorine, ensuring adequate fresh air ventilation — affect trichloramine concentrations significantly and are modifiable through facility management decisions.

The home air quality dimension

Repeated visits to indoor pools can bring chloramine residues home on skin, hair, and wet swimwear. In poorly ventilated bathrooms or laundry areas where damp swimwear dries, these residual compounds continue releasing into indoor air. For family members with asthma, respiratory sensitivities, or reactive airways, this secondary exposure is worth considering.

Running an air purifier with activated carbon in areas where post-swim off-gassing occurs — bathrooms, mudrooms, laundry rooms — can help reduce airborne chemical compound concentrations. Activated carbon adsorbs gaseous chemical compounds from the air, addressing the specific category of pollutant that chloramine byproducts represent. True HEPA filtration in the same unit handles any fine particulate matter introduced during pool visits.

The iAdaptAir by Air Oasis combines both technologies with UV-C light and bipolar ionization in a single CARB-certified ozone-free unit. The 2S model, covering up to 265 square feet, is appropriate for a bathroom or changing area. The 2M, at 530 square feet, works well for larger mudrooms, laundry rooms, or open-plan living areas. Maintain the minimum 4-inch clearance around all inlets and outlets, and keep the unit running consistently for sustained reduction in airborne compounds.

Swimming is still worth it — with the right context

The research on pool chemicals and respiratory health does not argue against swimming. It argues for nuance. Recreational swimming, particularly outdoors, carries a very different risk profile than years of daily competitive training in an indoor natatorium. For the vast majority of swimmers, the respiratory benefits of aerobic exercise, the warm humid air, and the low-impact nature of the sport outweigh the risks associated with chloramine exposure.

What the research does support is informed attention to pool ventilation quality, pre-swim hygiene practices, and clinical evaluation for anyone who consistently develops respiratory symptoms after pool sessions, particularly if those symptoms persist for hours afterward. If your symptoms correlate with pool visits and don't respond to the usual approaches, an allergist or pulmonologist can evaluate for exercise-induced bronchoconstriction, airway hyperresponsiveness, or other conditions that pool environments may be bringing to the surface.

Shop Air Oasis today and find the iAdaptAir model sized for your home. Because protecting your air doesn't stop at the pool's edge.