Chlorinated Swimming Pools Research Articles

Amoebicidal effect of chlorine dioxide gas against pathogenic Naegleria fowleri and Acanthamoeba polyphaga.

The pathogenic free-living amoebae, Naegleria fowleri and Acanthamoeba polyphaga, are found in freshwater, soil, and unchlorinated or minimally chlorinated swimming pools. N. fowleri and A. polyphaga are becoming problematic as water leisure activities and drinking water are sources of infection. Chlorine dioxide (ClO2) gas is a potent disinfectant that is relatively harmless to humans at the concentration used for disinfection. In this study, we examined the amoebicidal effects of ClO2 gas on N. fowleri and A. polyphaga. These amoebae were exposed to ClO2 gas from a ready-to-use product (0.36 ppmv/h) for 12, 24, 36, and 48h. Microscopic examination showed that the viability of N. fowleri and A. polyphaga was effectively inhibited by treatment with ClO2 gas in a time-dependent manner. The growth of N. fowleri and A. polyphaga exposed to ClO2 gas for 36h was completely inhibited. In both cases, the mRNA levels of their respective actin genes were significantly reduced following treatment with ClO2 gas. ClO2 gas has an amoebicidal effect on N. fowleri and A. polyphaga. Therefore, ClO2 gas has been proposed as an effective agent for the prevention and control of pathogenic free-living amoeba contamination.

In silico discovery of diagnostic/vaccine candidate antigenic epitopes and a multi-epitope peptide vaccine (NaeVac) design for the brain-eating amoeba Naegleria fowleri causing human meningitis

Naegleria fowleri, the brain-eating amoeba, is a free-living amoeboflagellate with three different life cycles (trophozoite, flagellated, and cyst) that lives in a variety of habitats around the world including warm freshwater and soil. It causes a disease called naegleriasis leading meningitis and primary amoebic meningoencephalitis (PAM) in humans. N. fowleri is transmitted through contaminated water sources such as insufficiently chlorinated swimming pool water or contaminated tap water, and swimmers are at risk. N. fowleri is found all over the world, and most infections were reported in both developed and developing countries with high mortality rates and serious clinical findings. Until now, there is no FDA approved vaccine and early diagnosis is urgent against this pathogen. In this study, by analyzing the N. fowleri vaccine candidate proteins (Mp2CL5, Nfa1, Nf314, proNP-A and proNP-B), it was aimed to discover diagnostic/vaccine candidate epitopes and to design a multi-epitope peptide vaccine against this pathogen. After the in silico evaluation, three prominent diagnostic/vaccine candidate epitopes (EAKDSK, LLPHIRILVY, and FYAKLLPHIRILVYS) with the highest antigenicities were discovered and a potentially highly immunogenic/antigenic multi-epitope peptide vaccine (NaeVac) was designed against the brain-eating amoeba N. fowleri causing human meningitis.

Unexpected trends of amoebic encephalitis in Pakistan.

Annual reported cases of Naegleria fowleri (NF), popularly known as brain eating amoeba, are becoming a huge challenge for Pakistani health authorities. Karachi has seen cases regularly up till the present but Lahore has not. The spread of this amoeba in non-chlorinated water is a major concern for the authorities. NF is an amoeba commonly found in warm freshwater environments such as lakes, hot springs and poorly chlorinated swimming pools. It poses a significant risk during hot weather when water-related recreational activities are popular. Where there is a non-chlorinated water supply, its spread is aggravated.

Exploring the health and energy savings dilemma in swimming facilities and the potential influence of Positive Energy Districts

Positive energy districts (PED) are neighborhoods with a net positive energy balance with the main goal to create sustainable districts that contribute to the energy transition. The three pillars energy efficiency, renewable energy, and energy flexibility forms the foundation of PEDs, and ‘Quality of life’ is one of the key principles.Indoor swimming facilities for recreation and sports, also called aquatic centers or swimming halls, are important for healthy lifestyles. They are highly energy-demanding facilities due to the large volumes and strict heating- and ventilation requirements to ensure the health of staff, visitors, and bathers. The large energy consumption indicates good potential to reduce their energy use. One possibility might be to include aquatic centers in PEDs: the district could support the facility with locally produced renewable energy. There are also studies that investigates innovative solutions regarding aquatic centers that might have potential to increase resilience and flexibility in the district.However, one important aspect in studies on energy use in aquatic centers that is often neglected is the presence of disinfection by-products (DBP), which are found in the air and water of chlorinated swimming pools. Several DBPs can lead to health issues, such as asthma, eye irritation, and even cancer.There are often conflicting goals in studies on swimming halls. The connection between DBP and energy is currently missing, and it could lead to projects compromising health over energy savings. Based on a literature review, this study highlights the research gap between DBPs and energy use in swimming facilities. A suggestion is also presented to integrate swimming halls into PEDs with the aim of increasing possibilities for a healthy lifestyle, supporting the aquatic center’s energy demand with renewable energy, and exploring new solutions for flexibility and resilience in the district.

Full-scale multisampling and empirical modeling of DBPs in water and air of indoor pools.

Disinfection by-products (DBPs) are formed in the water in swimming pools due to reactions between disinfectants (chlorine, bromine, ozone) and the organic matter introduced by bathers and supply water. High concentrations of DBPs are also reported in the air of indoor swimming pools. Based on a robust multisampling program, the levels and variations of DBPs in the air (trichloramine [TCAM] and trihalomethanes [THMs]) and water (THM) were assessed, as well as their precursors (total organic carbon, water temperature, pH, free, and total chlorine) and proxies (CO2 and relative humidity) in four indoor chlorinated swimming pools. High-frequency sampling was conducted during one high-attendance day for each pool. This study focused on parameters that are easy to measure in order to develop models for predicting levels of THMs and TCAM in the air. The results showed that the number of bathers had an important impact on the levels of THMs and TCAM, with a two-to-three-fold increase in air chloroform (up to 110 μg/m3) and a two-to-four-fold increase in TCAM (up to 0.52 mg/m3) shortly after pools opened. The results of this study for the first time showed that CO2 and relative humidity can serve as proxies for monitoring variations in airborne THMs and TCAM. Our results highlight the good predictive capacity of the developed models and their potential for use in day-to-day monitoring. This could help optimize and control DBPs formation in the air of indoor swimming pools and reduce contaminant exposure for both pool employees and users.

Review on the management of water quality for bio-mineral swimming pools in Western Europe.

In this review, we depict the state of the art concerning the water quality management of bio-mineral bathing pools, and compare these to traditional swimming pools. Bio-mineral pools use a combination of mechanic filtration, bio-filtration, and UV-treatment to disinfect the water. Studies in test tanks have shown that bio-filtration is effective in maintaining the water quality with regard to the treatment of organic pollution. Concerning biological risks, the bio-mineral pool relies on UV-treatment to degrade bacteria. Unlike chemical disinfectant treatments, UV disinfection does not lose its effectiveness in the event of high traffic in the pool. However, as only the water taken up by the filtration system is disinfected, it is essential that all the water in the pool is filtered. If the pool has a dead zone, its water is not disinfected and there is a risk of localized pathogen development. As the development of bio-mineral pools spreads in Europe, legislation gradually follows. The health parameters measured differ slightly from one country to another, but there are constants: the measurement of Escherichia coli, Enterococci, and Pseudomonas aeruginosa. In terms of biological swimming pools, regulatory homogeneity across Europe does not exist. From these comparisons, Austrian legislation segmenting water quality into 4 categories ranging from "excellent" to "poor" represents legislation that combines health and safety with indications of possible malfunctions. Next, a study of three real sites of bio-mineral pools is presented. It appears that whatever the type of pool, bio-mineral filtration makes it possible to achieve performances comparable to those encountered in chlorinated swimming pools concerning the risks associated with fecal contamination and external pollution. On the other hand, when frequentation is high, as is the case in small pools used for aquafitness, monitoring the risks of inter-bather contamination, as illustrated by the presence of Staphylococcus aureus, reveals a recurring problem. Knowing that this parameter is not evaluated in bathing waters in the natural environment and that numerous studies show that Staphyloccocus aureus are always detected, even on beaches, we propose the definition of three thresholds: i.e., 0CFU/100mL (threshold value in Wallonia) for water of excellent quality, less than 20CFU/100mL (threshold value in France) for water of very good quality, less than 50CFU/100mL (contribution of bathers by simple immersion) for good quality water, and more than 50CFU/100mL for poor quality water. This document could therefore be converted into a manual for operators on the use and management of bio-mineral baths.

Modeling the formation of disinfection byproducts in chlorinated swimming pool water: Role of body fluid analog

Abstract The recirculation of pool water and the continuous input of pollutants and disinfectants in swimming pools intensifies the accumulation of disinfection byproducts (DBPs), which have received increasing attention. Trihalomethanes (THMs) are the most common DBPs found in swimming pool water. Developing a predictive THM model is an efficient and promising way to optimize the chlorine dosage and guarantee water safety. Because the main components of swimmer inputs and their respective quantities have been formalized and determined through body fluid analogs (BFA), the model development can rely on the chlorination of BFA components and mixtures. In this study, a well-established second-order reaction chlorine decay model with a variable reaction rate coefficient was expanded to describe the chlorine consumption in swimming pool water. The THM model with a variable formation coefficient was first developed based on the identical assumption of the chlorine model, that is, the reactivity of the reactants decreases as the reaction progresses. The results showed that uric acid exhibited the fastest initial rate coefficient for chlorine decay. Although citric acid showed a considerably high specific THM formation potential (μmol-THM, species/mg productive chlorine consumption), urea and humic acid (HA) were attributed to the fast-reacting THM formation precursors. The rate coefficients of urea and HA were higher than that of citric acid. For the mixture, the (overall) reaction rate coefficients were formulated as a function of the rate coefficient of the individual substance and the concentration of the substance remaining in the water. This concept was tested using BFA and BFA with HA. The model accurately described the chlorine consumption and THM concentrations (R2 > 0.96).

Long-Term Monitoring of Water and Air Quality at an Indoor Pool Facility during Modifications of Water Treatment

Previous research has shown that volatile disinfection byproducts (DBPs) can adversely affect the human respiratory system. As a result, swimming pool water treatment processes can play important roles in governing water and air quality. Thus, it was hypothesized that water and air quality in a swimming pool facility can be improved by renewing or enhancing one or more components of water treatment. This study is designed to identify and quantify changes in water and air quality that are associated with changes in water treatment at an indoor chlorinated swimming pool facility. Reductions in aqueous trichloramine (NCl3) concentration were observed following the use of secondary oxidizer with its activator. This inclusion also resulted in significant decreases in the concentrations of cyanogen chloride (CNCl) in pool water. The concentration of urea, a compound that is common in swimming pools and that functions as an important precursor to NCl3 formation, as well as a marker compound for the introduction of contaminants by swimmers, was also reduced after the addition of the activator. Concentrations of gas-phase NCl3 did not decrease after the treatment processes were changed. The collection of long-term water and air quality measurements also allowed for an assessment of the effects of bather load on water and air quality. In general, the concentrations of urea (an NCl3 precursor), liquid-phase NCl3, and gas-phase NCl3 all increased during periods of high swimmer number.

Inactivation of SARS-CoV-2 in chlorinated swimming pool water

SARS-CoV-2 transmission remains a global problem which exerts a significant direct cost to public health. Additionally, other aspects of physical and mental health can be affected by limited access to social and exercise venues as a result of lockdowns in the community or personal reluctance due to safety concerns. Swimming pools reopened in the UK on April 12th 2021, but the effect of swimming pool water on inactivation of SARS-CoV-2 has not yet been directly demonstrated. Here we demonstrate that chlorinated water which adheres to UK swimming pool guidelines is sufficient to reduce SARS-CoV-2 infectious titre by at least 3 orders of magnitude.

Real-Time Measurements of Gas-Phase Trichloramine (NCl3) in an Indoor Aquatic Center.

NCl3 is formed as a disinfection byproduct in chlorinated swimming pools and can partition between the liquid and gas phases. Exposure to gas-phase NCl3 has been linked to asthma and can irritate the eyes and respiratory airways, thereby affecting the health and athletic performance of swimmers. This study involved an investigation of the spatiotemporal dynamics of gas-phase NCl3 in an aquatic center during a collegiate swim meet. Real-time (up to 1 Hz) measurements of gas-phase NCl3 were made via a novel on-line derivatization cavity ring-down spectrometer and a proton transfer reaction time-of-flight mass spectrometer. Significant temporal variations in gas-phase NCl3 and CO2 concentrations were observed across varying time scales, from seconds to hours. Gas-phase NCl3 concentrations increased with the number of active swimmers due to swimming-enhanced liquid-to-gas transfer of NCl3, with peak concentrations between 116 and 226 ppb. Strong correlations between concentrations of gas-phase NCl3 with concentrations of CO2 and water (relative humidity) were found and attributed to similar features in their physical transport processes in pool air. A vertical gradient in gas-phase NCl3 concentrations was periodically observed above the water surface, demonstrating that swimmers can be exposed to elevated levels of NCl3 beyond those measured in the bulk air.

Human exposure to air contaminants in sports environments.

The aim of this review was to investigate human exposure to relevant indoor air contaminants, predictors affecting the levels, and the means to reduce the harmful exposure in indoor sports facilities. Our study revealed that the contaminants of primary concern are the following: particulate matter in indoor climbing, golf, and horse riding facilities; carbon dioxide and particulate matter in fitness centers, gymnasiums, and sports halls; Staphylococci on gymnasium surfaces; nitrogen dioxide and carbon monoxide in ice hockey arenas; carbon monoxide, nitrogen oxide(s), and particulate matter in motor sports arenas; and disinfection by-products in indoor chlorinated swimming pools. Means to reduce human exposure to indoor contaminants include the following: adequate mechanical ventilation with filters, suitable cleaning practices, a limited number of occupants in fitness centers and gymnasiums, the use of electric resurfacers instead of the engine powered resurfacers in ice hockey arenas, carefully regulated chlorine and temperature levels in indoor swimming pools, properly ventilated pools, and good personal hygiene. Because of the large number of susceptible people in these facilities, as well as all active people having an increased respiratory rate and airflow velocity, strict air quality requirements in indoor sports facilities should be maintained.

Oral nitrate reduction is not impaired after training in chlorinated swimming pool water in elite swimmers.

This study tested the hypothesis that exposure to chlorine-sterilised pool water would impair oral nitrate reduction (ONR). ONR was assessed in elite swimmers before and after morning and afternoon pool-based training. Nonswimmers were only assessed in the morning. ONR was similar in swimmers and nonswimmers (P= 1.000) and unchanged before and after morning and afternoon training (P≥ 0.341). Therefore, exposure to chlorinated pool water does not interfere with ONR. Novelty Exposure to chlorine-sterilised pool water does not impair oral nitrate reduction in elite swimmers.

Demonstration and Characterization of Cyst-Like Structures in the Life Cycle of Trichomonas vaginalis.

Trichomonas vaginalis is the parasitic protozoan residing in human urogenital tract causing trichomoniasis, which is the leading non-viral sexually transmitted disease. It has cosmopolitan distribution throughout the globe and affects both men and women. Lifecycle of the parasite has been traditionally described as consisting of motile and symptom-causing trophozoites. Chemical and temperature perturbations in trophozoites have been shown to aid conversion to pseudocysts, which is poorly investigated. In the current study, we show the formation of viable cyst-like structures (CLS) in stationary phase of T. vaginalis axenic culture. We used a fluorescent stain called calcofluor white, which specifically binds to chitin and cellulose-containing structures, to score for T. vaginalis CLS. Using flow cytometry, we demonstrated and quantitated the processes of encystation as well as excystation; thus, completing the parasite's lifecycle in vitro without any chemical/temperature alterations. Like cysts from other protozoan parasites such as Entamoeba histolytica and Giardia lamblia, T. vaginalis CLS appeared spherical, immotile, and resistant to osmotic lysis and detergent treatments. Ultrastructure of CLS demonstrated by Transmission Electron Microscopy showed a thick electron-dense deposition along its outer membrane. To probe the physiological role of CLS, we exposed parasites to vaginal pH and observed that trophozoites took this as a cue to convert to CLS. Further, upon co- culturing with cells of cervical origin, CLS rapidly excysted to form trophozoites which abrogated the cervical cell monolayer in a dose-dependent manner. To further corroborate the presence of two distinct forms in T. vaginalis, we performed two-dimensional gel electrophoresis and global, untargeted mass spectrometry to highlight differences in the proteome with trophozoites. Interestingly, CLS remained viable in chlorinated swimming pool water implicating the possibility of its role as environmentally resistant structures involved in non-sexual mode of parasite transmission. Finally, we showed that symptomatic human patient vaginal swabs had both T. vaginalis trophozoites and CLS; thus, highlighting its importance in clinical infections. Overall, our study highlights the plasticity of the pathogen and its rapid adaption when subjected to stressful environmental cues and suggests an important role of CLS in the parasite's life cycle, pathogenesis and transmission.

500 days of swimmers: the chemical water quality of swimming pool waters from the beginning.

Many studies of disinfection by-products (DBPs) in pools have focused on haloacetic acids, trihalomethanes, and chloramines, with less studies investigating the occurrence of other DBPs, such as haloketones, haloacetaldehydes, haloacetonitriles, halonitromethanes, and haloacetamides. Furthermore, while many studies have achieved a broadscreen analysis across several pools, fewer studies have followed the water quality of pools over time, with information regarding the production and fate of DBPs in pools over extended periods (e.g. > 1 year) being limited. This study reports the occurrence of 39 DBPs and several general water quality parameters in two newly built and filled swimming pools over 15 months, where investigations began prior to opening. DBP concentrations measured in this study were generally similar to or higher than those previously reported in chlorinated pools, with concentrations of chloroacetic acid, dichloroacetic acid, trichloroacetic acid, and chloral hydrate (trichloroacetaldehyde) in some samples being higher than previously reported maximum concentrations. Considering both pools, lower concentrations of DBPs were measured in the pool where a steady state non-purgeable organic carbon concentration was achieved, highlighting the importance of the establishment of a steady state balance of mineralisation versus addition of organic carbon to reduce precursors for DBP formation in pools. Pools were found to exhibit significantly higher estimated cytotoxicity than their filling water, which reflects the significantly higher concentrations of DBPs measured in the pools in comparison to the filling water. Chloral hydrate accounted for up to 99% the total estimated cytotoxicity and was found to be correlated to the number of pool entries, suggesting that swimmers may be a potential source of chloral hydrate precursors in pools. The presence and subsequent peak of non-purgeable organic carbon and DBPs prior to, and soon after, opening suggest that the building process and/or new pool infrastructure may have had a significant impact on the chemical water quality, particularly on DBP formation. This study includes the first quantification of bromochloroacetaldehyde, bromodichloroacetaldehyde, bromochloronitromethane, and dichloronitromethane in chlorinated swimming pools, and provides important new knowledge on the long-term trends of DBPs in pools.

Exhaled nitric oxide as a marker of chlorine exposure in young asthmatic swimmers

BackgroundSwimming is recommended for people with asthma. However, the inevitable exposure to chlorine and its disinfectant byproducts in indoor swimming pools could be responsible for bronchial inflammation and asthma development. Fractional exhaled nitric oxide (FeNO) is a noninvasive marker of airway inflammation that predicts asthma exacerbations. ObjectivesTo evaluate pretraining and posttraining FeNO levels in young swimmers with asthma attending an indoor chlorinated pool compared with a set of healthy swimmers and to examine the potential risk of exposure to chlorine as a factor associated with bronchial inflammation. MethodsA total of 146 children (8-18 years old) constantly attending an indoor chlorinated swimming pool were enrolled. Spirometry and FeNO measurements were performed 30 minutes after their arrival at the pool and immediately after exercise. Pre-exercise and postexercise spirometric and FeNO levels were assessed in a random subgroup of 14 swimmers (10 with asthma and 4 without) who performed cardiopulmonary exercise testing. ResultsAsthma was detected in 23 swimmers. In swimmers with asthma, preswimming FeNO values were significantly elevated compared with swimmers without asthma and their FeNO values measured before cardiopulmonary exercise testing. Postexercise FeNO values were significantly decreased by approximately one-third in healthy children and children with asthma in all sporting backgrounds. However, postswimming FeNO values remained significantly higher in swimmers with asthma compared with those without asthma. Forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), and FEV1/FVC ratio values showed no significant difference before and after 2 types of activity. ConclusionElevated FeNO levels before and after swimming were recorded in swimmers with asthma not observed in a different exercise field. The presence of chlorine in the indoor swimming pool seems to explain this finding.

Does access to saltwater swimming pools reduce ear pathology and hearing loss in school children of remote arid zone aboriginal communities? A prospective 3-year cohort study.

To assess whether access to saltwater chlorinated swimming pools in remote Aboriginal communities is beneficial in reducing levels of middle ear disease and hearing loss in school children. A prospective 3-year cohort study of children in 10 remote Aboriginal communities in South Australia with (n=4) or without (n=6) swimming pools. Outback Australia. Eight hundred and thirteen school-age children residing in remote South Australia. Prevalence of open and closed middle ear disease and prevalence of hearing loss. About 2107 ear assessments were conducted during the study period. 70.7% of children in communities with pools failed a screening test of hearing compared with 68.6% of children in non-pool communities (P=0.637). 32.3% of children had chronic otitis media (COM). There was no difference between pool and non-pool communities in the frequency of either inactive (19.4% pool vs 22.6% non-pool; P=0.232) or active (19.8% pool vs 17.8% non-pool; P=0.383) COM. In children with bilateral intact tympanic membranes, 21.2% had unilateral and 20.6 had bilateral type B tympanograms. There was no difference between pool and non-pool communities in the frequency of type B tympanometry (P=0.465). Hearing loss associated with both open and closed middle ear disease remains highly prevalent in children living in remote Aboriginal communities in South Australia. Access to swimming pools in this population does not appear to significantly reduce these high levels of middle ear disease or associated hearing loss.

Predicting health risk from exposure to trihalomethanes in an Olympic-size indoor swimming pool among elite swimmers and coaches

ABSTRACTDisinfection by-products (DBP) such as trihalomethanes (THM) are formed when chlorine and bromine interact with natural organic materials in chlorine-treated swimming pools. Epidemiological evidence demonstrated an association between exposure to swimming pool environment and adverse health effects. Therefore, this study aimed to assess carcinogenic and non-carcinogenic risk of long-term exposure of elite swimmers and their coaches. In an Olympic-size indoor chlorinated swimming pool, THM levels were determined in water (21–69 µg/L), in the boundary layer above the water surface (59–397 µg/m3), and in the air surrounding the pool (28–390 µg/m3). These values were used to predict multi-pathway chronic daily intake (CDI), cancer risk (CR) and hazard index (HI). Oral and dermal CDI for swimmers were 2.4 × 10−6 and 2.0 × 10−8, respectively. The swimmers’ inhalation CDI (1.9 × 10−3 mg/kg/day) was estimated to be sixfold higher than levels obtained for coaches (3.3 × 10−4 mg/kg/day). According to guidelines, the HI was acceptable, but CR exceeded the recommended limit for both, coaches (CR: 5.5 × 10−7–8.5 × 10−5; HI: 6.5 × 10−4–1 × 10−1) and swimmers (CR: 1.4 × 10−5–3.6 × 10−4 HI: 1.6 × 10−2–4.3 × 10−1). Our findings provide further support to the need to develop comprehensive guidelines to safeguard the health of individuals involved in elite swimming.

An exploration of disinfection by-products formation and governing factors in chlorinated swimming pool water.

This paper investigates disinfection by-products (DBPs) formation and their relationship with governing factors in chlorinated swimming pools. The study compares concentrations of DBPs with WHO guidelines for drinking water quality recommended to screen swimming pool water quality. The statistical analysis is based on a global database of 188 swimming pools accumulated from 42 peer-reviewed journal publications from 16 countries. The mean and standard deviation of dichloroacetic acid and trichloroacetic acid were estimated as 282 ± 437 and 326 ± 517 μg L-1, respectively, which most often surpassed the WHO guidelines. Similarly, more than half of the examined pools had higher values of chloral hydrate (102 ± 128 μg L-1). The concentration of total chloramines (650 ± 490 μg L-1) was well above the WHO guidelines in all reported cases. Nevertheless, the reported values remained below the guidelines for most of the studied pools in the case of total trihalomethanes (134 ± 160 μg L-1), dichloroacetonitrile (12 ± 12 μg L-1) and dibromoacetonitrile (8 ± 11 μg L-1). Total organic carbon, free residual chlorine, temperature, pH, total nitrogen and bromide ions play a pivotal role in DBPs formation processes. Therefore, proper management of these governing factors could significantly reduce DBPs formation, thereby, contributing towards a healthy swimming pool environment.

Early life swimming pool exposure and asthma onset in children \u2013 a case-control study

BackgroundTrichloramine exposure in indoor swimming pools has been suggested to cause asthma in children. We aimed to investigate the risk of asthma onset among children in relation to individual trichloramine exposure.MethodsA longitudinal nested case-control study of 337 children with asthma (cases) and 633 controls aged 16–17 years was performed within a population-based cohort from The Obstructive Lung Disease in Northern Sweden studies (OLIN). Year of asthma onset and exposure time at different ages were obtained in telephone interviews. Trichloramine concentrations in the pool buildings were measured. Skin prick test results for inhalant allergens were available from previous examinations of the cohort. The risk for asthma was analyzed in relation to the cumulative trichloramine exposure before onset of asthma.ResultsThe participation rate was high in the original cohort (88 to 96%), and in the case-control study (80%). Trichloramine concentrations ranged from 0.020 to 0.55 mg/m3 (mean 0.15 mg/m3). Swimming pool exposure in early life was associated with a significantly higher risk of pre-school asthma onset. A dose-response relationship between swimming pool exposure and asthma was indicated in children with asthma onset at 1 year of age. Children who were both sensitized and exposed had a particularly high risk.ConclusionsEarly life exposure to chlorinated swimming pool environments was associated with pre-school asthma onset.

Characterization of the bacterial community in shower water before and after chlorination.

Bathers release bacteria in swimming pool water, but little is known about the fate of these bacteria and potential risks they might cause. Therefore, shower water was characterized and subjected to chlorination to identify the more chlorine-resistant bacteria that might survive in a chlorinated swimming pool and therefore could form a potential health risk. The total community before and after chlorination (1 mg Cl2 L-1 for 30 s) was characterized. More than 99% of the bacteria in the shower water were Gram-negative. The dominant bacterial families with a relative abundance of ≥10% of the total (non-chlorinated and chlorinated) communities were Flavobacteriaceae (24-21%), Xanthomonadaceae (23-24%), Moraxellaceae (12-11%) and Pseudomonadaceae (10-22%). The relative abundance of Pseudomonadaceae increased after chlorination and increased even more with longer contact times at 1 mg Cl2L-1. Therefore, Pseudomonadaceae were suggested to be relatively more chlorine resistant than the other identified bacteria. To determine which bacteria could survive chlorination causing a potential health risk, the relative abundance of the intact cell community was characterized before and after chlorination. The dominant bacterial families in the intact community (non-chlorinated and chlorinated) were Xanthomonadaceae (21-17%) and Moraxellaceae (48-57%). Moraxellaceae were therefore more chlorine resistant than the other identified intact bacteria present.