Chlorine and chloramine exposure can produce complications ranging from mild irritation of the eyes, skin, and airways to life-threatening conditions like acute respiratory distress syndrome, hemolytic anemia, and, with long-term ingestion of disinfection byproducts, an elevated risk of bladder cancer. The severity depends on the form of the chemical, the concentration, the route of exposure, and how long it lasts. Because chlorine and chloramine are used to treat nearly all public drinking water and are present in swimming pools, cleaning products, and industrial settings, understanding the full spectrum of possible complications is more relevant to everyday life than most people realize.
Acute Respiratory Effects
Chlorine gas sits at a middle point on the water-solubility scale for inhaled irritants, and that matters. Highly soluble gases tend to attack the nose and throat first, giving you an early warning. Chlorine does irritate the upper airways, but because of its intermediate solubility, it also penetrates deeper into the lungs, causing delayed lower-airway symptoms driven largely by the release of hypochlorous acid and hydrochloric acid on contact with moist tissue.1Toxicology Letters. Choking agents and chlorine gas – History, pathophysiology, clinical effects and treatment Common acute symptoms include wheezing, cough, chest tightness, and difficulty breathing. Clinical signs can include low blood oxygen, abnormal lung sounds, and changes visible on a chest X-ray.2PubMed Central. Chlorine gas inhalation: human clinical evidence of toxicity and experience in animal models
At higher concentrations, the complications escalate quickly. Swelling of the glottis or sudden spasm of the larynx can become immediately life-threatening. Toxic pneumonitis, fluid accumulation in the lungs, and acute respiratory distress syndrome are all documented consequences of significant chlorine inhalation.1Toxicology Letters. Choking agents and chlorine gas – History, pathophysiology, clinical effects and treatment Eye exposure can cause conjunctival redness, corneal abrasions, and chemical burns of the mouth and throat lining. Chloramine gas, produced when bleach and ammonia are mixed, triggers a very similar clinical picture, and mixing these common household products has caused mass-casualty incidents.3PubMed. Mass casualties from acute inhalation of chloramine gas
When Airway Problems Persist
Some people recover fully from an acute chlorine exposure. Others do not. A condition called reactive airways dysfunction syndrome, or RADS, can develop after a single large dose of chlorine and leave a person with chronic symptoms resembling asthma: persistent coughing, wheezing, and abnormal lung-function tests. A systematic review covering over 1,300 participants across 11 countries found that among the 170 individuals diagnosed with RADS and followed over time, the most frequent outcome was long-term persistence of symptoms and measurable changes in lung function, particularly among workers exposed on the job.4Revista Brasileira de Saúde Ocupacional. Chlorine gas exposure and evolutive patterns of reactive airways dysfunction syndrome: a systematic review
Animal studies help explain why this happens. In the deeper airways, a type of lining cell called a basal cell can regenerate damaged tissue fairly efficiently. But the smallest, most distal airways lack these progenitor cells, so damage there heals poorly, leading to chronic inflammation and scarring.5PubMed Central. Persistent effects of chlorine inhalation on respiratory health Mouse models of chlorine exposure confirm that even a single exposure can produce delayed, long-lasting airway hyperresponsiveness that mirrors the human condition, and the effect is dose-dependent.6PubMed. Inhalation of chlorine causes long-standing lung inflammation and airway hyperresponsiveness in a murine model of chemical-induced lung injury The practical upshot is that someone who has had a serious chlorine exposure should expect follow-up lung-function testing, because RADS can declare itself weeks after the acute event has resolved.
Indoor Pool Exposure and Trichloramine
You do not need an industrial accident to inhale enough chlorine byproducts to cause harm. Indoor swimming pools generate trichloramine, a volatile compound formed when chlorine reacts with nitrogen-containing compounds in sweat, urine, and skin oils. Trichloramine is the chemical behind the distinctive “pool smell” many people associate with chlorine itself, and it tends to concentrate in the air layer just above the water surface.
A study of volunteers with no prior pool exposure found measurable drops in lung function after breathing indoor pool air containing about 0.23 mg/m³ of trichloramine. Pool workers showed similar lung-function changes, and a nested case-control analysis among those workers found that the highest-exposed group had roughly double the odds of asthma, though the confidence interval was wide.7PubMed Central. Lung function in volunteers before and after exposure to trichloramine in indoor pool environments and asthma in a cohort of pool workers Lifeguards and swim instructors report more red eyes, runny nose, and voice loss than colleagues who work in the same facility’s office or café. At trichloramine levels above 0.5 mg/m³, the risk of runny nose tripled, red eyes tripled, and voice loss increased roughly three-and-a-half-fold compared with unexposed employees.8Journal of Exposure Science & Environmental Epidemiology. Airborne trichloramine (NCl3) levels and self-reported health symptoms in indoor swimming pool workers: dose-response relationships That 0.5 mg/m³ threshold aligns with the World Health Organization’s recommended occupational guideline, and these findings suggest that the guideline is protective for most workers but that poorly ventilated pools can exceed it.
Skin and Allergic Sensitization
Prolonged contact with chlorinated water strips the skin’s natural oils and disrupts its barrier function. Hydrotherapists and pool workers who spend hours in chlorinated water are at elevated risk for contact dermatitis, with the risk climbing when pools use gaseous chlorine (which can temporarily drop the water’s pH, making it more aggressive) rather than other chlorine-based disinfectants.9PubMed. The effect of physical and chemical properties of swimming pool water and its close environment on the development of contact dermatitis in hydrotherapists For casual swimmers, the effect is usually mild dryness and itching that resolves quickly. For people who are in the water daily, the damage accumulates.
There is also experimental evidence suggesting that chlorination products can promote allergic sensitization by compromising the barrier function of epithelial tissues, essentially making it easier for allergens to cross into the body.10PubMed. Chlorination products: emerging links with allergic diseases This line of research is still developing, but it offers one plausible mechanism behind the observation that frequent pool attendance correlates with higher rates of allergic conditions in some populations. The evidence is not strong enough to warrant avoiding pools, but it does suggest that rinsing off chlorinated water promptly and moisturizing afterward is more than cosmetic advice.
Eye Damage From Chlorinated Water
Red, stinging eyes after swimming are almost a cliché, but the damage goes beyond temporary discomfort. Controlled experiments using confocal microscopy have shown that exposure to chlorine at swimming-pool concentrations damages corneal epithelial cells and disrupts the corneal barrier. Eyes rinsed with chlorinated saline showed significantly increased fluorescein uptake, a marker of surface damage, compared with eyes rinsed in plain saline, distilled water, or tap water. The researchers concluded that swimming without goggles could be a risk factor for corneal epithelial integrity and recommended goggle use.11Cornea. Deleterious Effects of Swimming Pool Chlorine on the Corneal Epithelium For competitive swimmers who log many hours in the water, the cumulative load on the corneal surface is a genuine concern, not just a nuisance.
Dental Erosion in Swimmers
One of the less-expected complications of chlorine exposure involves teeth. When pool water is improperly maintained and the pH dips below neutral, the acidic environment can erode dental enamel. A study at a gas-chlorinated pool found that only about 3% of non-swimmers reported symptoms consistent with enamel erosion, compared with 12% of recreational swimmers and 39% of competitive swim-team members. All four swimmers confirmed to have clinical enamel erosion had trained regularly for competitive meets.12PubMed. Erosion of dental enamel among competitive swimmers at a gas-chlorinated swimming pool
A later study confirmed that more than a quarter of competitive adolescent swimmers had dental erosion, compared with 10% of recreational swimmers. Competitive swimmers developed erosion on both the front and back surfaces of their anterior teeth, while recreational swimmers had it only on the palatal side, and the risk grew with more hours in the water.13PubMed Central. Prevalence of dental erosion in adolescent competitive swimmers exposed to gas-chlorinated swimming pool water The lesson is straightforward: pools need to keep their pH tightly controlled, and competitive swimmers should mention their training to their dentist.
Blood Complications in Dialysis Patients
For the general population, the concentrations of chlorine and chloramine in tap water are too low to affect blood chemistry. But dialysis patients are a major exception, because their blood is exposed directly to large volumes of water through the dialysis membrane. Chloramines pass through standard dialysis filters, reach the bloodstream, and oxidize hemoglobin in a two-pronged attack: both through their direct oxidizing power and by disabling the red blood cell’s own protective metabolism.14PubMed. Chlorinated urban water: a cause of dialysis-induced hemolytic anemia
The result is hemolytic anemia, where red blood cells are destroyed faster than the body can replace them, sometimes accompanied by methemoglobinemia, a condition in which hemoglobin loses its ability to carry oxygen. A recent case series described hemodialysis patients who developed cyanosis, dark brown blood, dizziness, shortness of breath, and headache during treatment sessions contaminated with excess chlorine.15PubMed. Methemoglobinemia in Hemodialysis Patients due to Acute Chlorine Intoxication: A Case Series Calling Attention on an Old Problem Even home dialysis setups are vulnerable. Two home hemodialysis patients developed severe hemolysis when mains water chloramine levels spiked above normal.16Hemodialysis International. When pure is not so pure: chloramine-related hemolytic anemia in home hemodialysis patients Chloramines are not removed by reverse osmosis or deionization; dialysis facilities must use granular activated carbon filtration or chemical reduction with ascorbic acid to neutralize them.17PubMed. Chloramine removal from water used in hemodialysis
Bladder Cancer and Disinfection Byproducts
When chlorine or chloramine reacts with natural organic matter in water, it creates disinfection byproducts, the most studied of which are trihalomethanes (THMs). The link between long-term THM exposure and bladder cancer is one of the best-documented chronic risks of water chlorination. A pooled analysis found that men exposed to average THM levels above 1 part per billion had about 24% higher odds of bladder cancer, and the risk rose to 44% higher at concentrations above 50 ppb.18PubMed. Disinfection byproducts and bladder cancer: a pooled analysis A more recent meta-analysis found a 59% increase in bladder cancer risk with long-term THM exposure compared with minimal exposure.19PubMed. Association between drinking water disinfection byproducts exposure and human bladder cancer: A time-updated meta-analysis of trihalomethanes
These numbers sound alarming, but context matters. Bladder cancer is a relatively uncommon disease, so even a 50-60% relative increase translates to a modest absolute increase in individual risk. And the alternative to chlorinating water is waterborne disease, which kills far more people globally than disinfection byproducts ever could. The practical takeaway is not to stop drinking tap water but to understand that long-term exposure to high THM levels is worth reducing when feasible, through point-of-use carbon filtration, for example.
NDMA and Chloramine-Specific Byproducts
Chloramine disinfection produces its own signature byproduct concern: N-nitrosodimethylamine, or NDMA, a probable human carcinogen. NDMA forms when monochloramine reacts with dimethylamine, a compound found naturally in source water.20PubMed. Formation of N-nitrosodimethylamine (NDMA) from dimethylamine during chlorination Water systems that use chloramination tend to produce higher NDMA levels than those using free chlorine. One study of two northeastern U.S. distribution systems found NDMA in 98% of all samples, with concentrations in the chloraminated system running roughly two to three times higher than in the chlorinated system.21PubMed Central. Low-level N-Nitrosamine occurrence in disinfected drinking water and relationships with standard water quality indicators
NDMA formation peaks around pH 7-8, which is the normal operating range for most water treatment plants, and increases with both monochloramine concentration and contact time.22Desalination. The hazard of N-nitrosodimethylamine (NDMA) formation during water disinfection with strong oxidants The concentrations detected are very low, typically measured in nanograms per liter, and many utilities monitor for NDMA even though no federal maximum contaminant level currently exists in the United States. But because NDMA is potent at extremely low concentrations, even these trace levels draw regulatory attention, and they represent a real trade-off that water utilities face when choosing between chlorine and chloramine as a secondary disinfectant.
Reproductive and Developmental Concerns
Whether disinfection byproducts cause birth defects has been studied extensively, and the evidence is genuinely mixed. A meta-analysis pooling available studies found a small but statistically significant 17% excess risk of congenital anomalies overall for high versus low exposure to THMs, along with a 58% excess risk for one specific heart defect, ventricular septal defects, though that estimate rested on just three studies and showed no clear dose-response pattern.23PubMed Central. Chlorination disinfection by-products in drinking water and congenital anomalies: review and meta-analyses The authors concluded that, on balance, there was “little evidence” of an association for most anomaly types.
A large U.S. case-control study examining nearly 2,700 participants found a broad range of positive, null, and negative estimates across eight specific heart defects and multiple byproduct species, and concluded there was no strong evidence linking congenital heart defects to byproduct exposure.24PubMed Central. Maternal Exposure to Tap Water Disinfection By-Products and Risk of Selected Congenital Heart Defects A more recent dose-response meta-analysis, however, found nonlinear relationships emerging at higher exposure levels, with increased risks for certain defects like anencephaly and musculoskeletal anomalies at THM concentrations above 60 micrograms per liter, and for low birth weight at term above 30 micrograms per liter.25PubMed. Exposure to disinfection by-products and risk of birth defects: A systematic review and dose-response meta-analysis The pattern that keeps repeating across this body of research is that effects are either absent or very small at the byproduct levels typical of well-regulated water systems, but may emerge at higher concentrations found in systems with heavy organic loading or inadequate treatment optimization.
Effects on Gut Bacteria
Because chlorine and chloramine are designed to kill microorganisms, a natural question is whether drinking treated water disrupts the bacteria living in your gut. The evidence so far is reassuring for most people. A study of Bangladeshi children found that chlorinated drinking water did not substantially change the overall richness or diversity of the gut microbiome. It did increase the abundance of certain genera associated with better gut health, though it also increased some antibiotic-resistance genes, possibly because of shifts in one bacterial family.26PubMed Central. Drinking water chlorination has minor effects on the intestinal flora and resistomes of Bangladeshi children
A study of Haitian infants told a slightly different story: households with detectable free chlorine residual in their water had infants with reduced microbial richness and diversity, along with higher abundance of Bifidobacterium, some species of which turned out to be chlorine-resistant in lab testing.27PubMed Central. Association between chlorine-treated drinking water, the gut microbiome, and enteric pathogen burden in young children in Haiti: An observational study Neither study suggests the effects are harmful in a meaningful clinical sense, and both research teams emphasized that the disease-prevention benefits of chlorination far outweigh these minor microbiome shifts. Still, the finding that chlorinated water might subtly favor certain resistant bacteria is worth watching as gut-health research matures.
Chloramine, Lead Pipes, and an Unexpected Infrastructure Risk
One of the most consequential complications of chloramine exposure has nothing to do with biology and everything to do with plumbing. When water utilities switch from free chlorine to chloramine as their residual disinfectant, the chemistry at the pipe surface changes. Lead pipes in older systems often develop a protective layer of lead dioxide on their inner walls. Free chlorine helps maintain that layer. Chloramine does not, and the switch can destabilize it, releasing dramatic amounts of lead into the water. In one set of experiments, total lead concentrations jumped from under 5 micrograms per liter to over 150 micrograms per liter when chloramine replaced free chlorine and no phosphate corrosion inhibitor was present.28Environmental Science & Technology. The Ability of Phosphate To Prevent Lead Release from Pipe Scale When Switching from Free Chlorine to Monochloramine For context, the EPA’s action level for lead in drinking water is 15 micrograms per liter.
Brass fixtures can also be affected. Experiments have shown that chloramines sometimes dramatically worsen lead leaching from brass compared with free chlorine.29Journal AWWA. role of chlorine and chloramine in corrosion of lead‐bearing plumbing materials This issue gained widespread public attention during the Flint, Michigan water crisis and remains a live concern in any city with aging lead service lines. Phosphate-based corrosion inhibitors can mitigate the problem, but the interaction between disinfectant type and pipe chemistry is something that needs active management, not just one-time testing.
Airborne Byproducts From Household Cleaning
You do not need to be near a swimming pool or a chemical plant to inhale chlorine-related compounds. Using bleach-containing household products in enclosed spaces like bathrooms and kitchens generates measurable levels of volatile organic compounds in indoor air. Chloroform concentrations during cleaning have been measured at 2.9 to 24.6 micrograms per cubic meter, and carbon tetrachloride concentrations spiked dramatically, with during-use levels averaging roughly 146 times the pre-use baseline in some applications. These elevated levels persisted at least 30 minutes after cleaning stopped. The implication is that routine bleach cleaning in a poorly ventilated bathroom creates meaningful inhalation exposure to several halogenated compounds, some of which are classified as possible carcinogens at high cumulative doses.
Who Is Most Vulnerable
The complications described throughout this article do not affect everyone equally. Several groups face disproportionate risk:
- Dialysis patients: Because their blood contacts water directly through a semipermeable membrane, even standard municipal chloramine levels can cause hemolytic anemia and methemoglobinemia if not properly filtered.
- Competitive swimmers: Daily multi-hour exposure to pool water and the trichloramine-laden air above it puts airways, eyes, and teeth at significantly higher risk than occasional recreational use.
- Indoor pool workers: Lifeguards, swim instructors, and maintenance staff accumulate chronic low-level trichloramine exposure that correlates with respiratory symptoms and reduced lung function.
- People with pre-existing asthma: Airway hyperresponsiveness from chlorine or trichloramine exposure tends to be worse in individuals whose airways are already inflamed.
- Residents with lead service lines: When a utility switches to chloramine, these households are at the front line of increased lead exposure unless corrosion control is properly adjusted.
- Pregnant women in areas with high THM levels: While the absolute risk increase is small and the evidence is inconsistent, the dose-response data suggest that very high byproduct levels may warrant attention.
For most people, the health benefits of water disinfection overwhelmingly outweigh these risks. Chlorine and chloramine prevent cholera, typhoid, and other waterborne diseases that still kill hundreds of thousands of people annually in regions without reliable treatment. The complications discussed here are real, but they are largely manageable through proper ventilation, protective equipment, filtration, and infrastructure maintenance. Knowing which complications exist and who is most at risk is the first step toward reducing exposure without giving up the enormous public health gains that water disinfection provides.