Vol.2, No.2, 68-78 (2010) Natural Science http://dx.doi.org/10.4236/ns.2010.22011 Copyright © 2010 SciRes. OPEN ACCESS Disinfection of swimming pools with chlorine and derivatives: formation of organochlorinated and organobrominated compounds and exposure of pool personnel and swimmers Maria-Cristina Aprea, Bruno Banchi, Liana Lunghini, Massimo Pagliantini, Antonio Peruzzi, Gianfranco Sciarra Laboratorio di Sanità Pubblica Area Vasta Toscana Sud Est, Azienda USL 7, Siena, Italy; maaprea@tin.it, c.aprea@usl7.toscana.it Received 12 August 2009; revised 11 September 2009; accepted 5 January 2010. ABSTRACT Chlorination of pool water leads to the forma- tion of many by-products, chloroform usually being the most abundant. The paper reports the results of a study evaluating exposure of bath- ers and pool employees to trihalomethanes (chloroform, bromodichloromethane, dibromo- chloromethane, bromoform) in four indoor swimming pools with chlorinated water. Chlo- roform concentrations in environmental air samples when the pool was in use (about 9 h), in the range 1-182 µg/m3, were greater near the pool than in the change rooms, passageways and offices. Chloroform concentrations in per- sonal air samples of pool employees were in the range 18-138 µg/m3. Urinary concentrations of chloroform averaged (geometric means) 0.123 and 0.165 µg/l and 0.404 and 0.342 µg/l prior and at the end of exposure during in water and out of water activities, respectively. The significant increase in urinary excretion of chloroform confirms that the source of the contaminant was pool water. Absorption of chloroform, estimated from airborne and water concentrations, was significantly correlated with delta chloroform (after/before exposure) and urinary concentra- tions of chloroform at the end of exposure. As chloroform is a toxic and possibly carcinogenic substance, these observations pose a problem principally for the general population of pool users. Keywords: Disinfection By-Products; Indoor Swimming Pool; Trihalomethanes; Biological Monitoring; Exposure; Urine 1. INTRODUCTION This paper is concerned with bathing complexes con- sisting of one or more artificial pools for recreational, educational, sporting or therapeutic activity carried out in the water. From the health point of view, pools are classified according to environmental and structural characteristics and type of use. Various documents de- fining guidelines for safe use of recreational facilities such as pools have been published [1-3]. Chemical haz- ards associated with frequentation of pools are summa- rized in Figure 1. Chemical agents in pool water depend on the type of water used to fill the pool. Town water, for example, may contain organic matter and by-products of disinfec- tion from previous treatments. Among the chemical agents derived from bathers, nitrogen compounds, espe- cially ammonia, react with free disinfectants to form various by-products. Nitrogen compounds may come from skin secretions: the nitrogen content of sweat is about 1 g/l as ammonia, amino acids, creatinine and urea. Significant quantities of nitrogen compounds can come from urine: urine release by bathers averages 25-30 ml/person [4] but may exceed 77.5 ml/person [5]. No information is currently available about concentrations of compounds from cosmetics. With regard to chemical agents from maintenance, a considerable number of compounds are used to keep water quality acceptable. Disinfectants are added in order to disactivate patho- genic microorganisms. Chlorine in one of its various forms is the most common. Other disinfectants such as ozone and UV radiation kill or inactivate microorgan- isms at the time of treatment but do not have any resid- ual effect that continues to act in the water. They are therefore used with chlorine or bromine to provide con- tinuous disinfection. Chlorine dioxide is not considered a chlorine disinfectant as it acts differently without pro- ducing residual chlorine, through conversion to chlorite
M. C. Aprea et al. / Natural Science 2 (2010) 68-78 Copyright © 2010 SciRes. OPEN ACCESS 69 CHEMICAL SUBSTANCES IN POOL Derived from maintenance Disinfectancts, Flocculants, Algicides Buffer chemicals Derived from bathers Urine, Perspiration, Dirt, Lotions (sun screens, cosmetics, residues of soap) Derived from water By-products of water treatment Precursors By-products of water treatment e.g. Trihalomethanes , Haloacetic acids , Clorathes, Nitrogen trichloride Figure 1. Summary of possible sources of chemical contami- nation in swimming pools. and chlorate ions that remain in solution. Liquid bromine is seldom used, whereas sodium bromide and its oxidant (hypochlorite) are more common. Disinfection with bromine compounds is not suitable for outdoor pools because sunlight destroys bromine residues. In all cases, the choice is based on efficacy in the particular circum- stances of use, as well as ease of handling and monitor- ing. Compounds used to correct pH depend on the type of disinfectant and its acidity/alkalinity. Alkaline disin- fectants such as sodium hypochlorite only require addi- tion of an acid, which is generally sodium hydrogensul- phate, carbon dioxide or hydrochloric acid. Acid disin- fectants such as chlorine require addition of an alkaline substance which is generally sodium carbonate solution. At correct doses with maintenance of pH between 7.2 and 8.0, disinfectants should not have adverse effects on health. Flocculants such as polyaluminium chloride can be used to facilitate removal of dissolved or suspended substances and colloids. They trap the substances in flocculate that can be removed by filtration. The formation of by-products of disinfection is related to the reaction of disinfectants with other chemical sub- stances in the water. The most abundant by-products are trihalomethanes, such as chloroform, the most abundant, together with haloacetic acids of which di- and tri- chloroacetic acids are the most abundant [6]. The pres- ence of inorganic bromides in the water can induce for- mation of bromine after oxidation, which can participate in the formation of by-products such as brominated tri- halomethanes. Use of ozone in the presence of bromides can lead to formation of bromates that can build up in the water if turnover is poor. Limited information is available on ozonation and its by-products. Ozone can react with oraganic substances to produce oxygenated compounds such as aldehydes and carboxylic acids. Chlorine and bromine react very quickly with ammonia forming chloramines and bromoamines. Little data is available on the impact of UV on disinfection by-prod- ucts when used with other chemicals, but UV does not seem to form by-products and appears to significantly reduce chloramine levels. Exposure of pool personnel and bathers may occur by ingestion of water, inhalation of aerosol or vapours and cutaneous absorption. The quantity of water ingested by swimmers depends on various factors, including experi- ence, gender, age and type of activity. Estimates show that water intake is higher in children (37 ml) than adults (16 ml), and in men (22 ml) than women (12 ml) [7]. Bathers inhale the air in contact with the water surface. The volume of air inhaled depends on the intensity of physical activity and exposure time. Exposure by inhala- tion regards substances in vapour form released by the water and aerosols created also by swimmer-induced splashing and stirring of the water. Concentrations at different levels in the air above the pool depends on fac- tors such as ventilation, the size of the building and air circulation. Skin, including eyes and mucous membranes, is extensively exposed to chemical agents in pool water. The intensity of skin absorption depends on a series of factors including contact time, water temperature and concentration of toxic compounds. Many by-products of disinfection have proven to be mutagenic, genotoxic, carcinogenic, fetotoxic, hepato- toxic, renotoxic, neurotoxic and dysmetabolic [8]. Chlo- roform and bromodichloromethane are classified by the International Agency for Research on Cancer (IARC) as possible carcinogens for humans (group 2B) [9], whereas the American Conference of Governmental In- dustrial Hygienists (ACGIH) considers chloroform to be carcinogenic for animals with unknown relevance to humans (Class A3) [10]. Concentrations of trihalomethanes in pool water [11-32] and in the air above the pool [11,14-16,18,26, 27,33,34] was examined in several studies. Some authors investigated also the absorption of trihalomethanes dur- ing time spent at the pool by measuring blood concentra- tions of chloroform or those in alveolar air [14-16,29, 35,36]. The aim of the present study was to assess exposure levels of swimmers and pool personnel to chlorinated and brominated organic compounds in public indoor pools. Airborne concentrations were determined in dif- ferent parts of the pool premises, and when possible, by personal air sampling and determination of urinary ex- cretion before and after exposure. Levels of the same compounds were also determined in water, as well as microclimatic and plant conditions. Absorption of chlo- roform estimated from airborne and water concentrations were compared with the increase in concentrations in urine during exposure. 2. MATERIALS AND METHODS 2.1. Microclimatic and Plant Conditions Four public indoor pools were monitored. All used drinking water from the town water supply. On days of monitoring, one or more water samples were taken for
M. C. Aprea et al. / Natural Science 2 (2010) 68-78 Copyright © 2010 SciRes. OPEN ACCESS 70 determination of brominated and chlorinated organic compounds (chloroform, bromodichloromethane, di- bromochloromethane, bromoform). Pool 1: pool volume 470 m3 plus compensation tank 20 m3, disinfectant calcium hypochlorite 65% and occa- sionally sodium dichloroisocyanate, air intake 18000 m3/h with aspiration of 15000 m3/h (turnover about 83%). The plant was monitored five times in 2006-2008. On sampling days, mean relative humidity was 51%- 68%, mean air temperature 23.5-28.5°C. Mean air speed was 0.10-0.23 m/sec. Water temperature was 28.6-29°C, pH 7.3-7.8, nitrates 8.3-15 mg/l, isocyanic acid 40-75 mg/l, turbidity 0.2-0.3 mg/l, suspended solids 0.9 mg/l and residual free chlorine 0.29-1.12 mg/l. Maximum number of users per hour was 50-60 and total daily users 150-200. Pool 2: pool volume 476.3 m3 plus compensation tank 24 m3, disinfectant sodium hypochlorite, air intake 30000 m3/h (turnover about 40%). The plant was moni- tored three times in 2007-2008. Mean relative humidity on sampling days was 70-75%, mean air temperature 23.2-24.5°C, mean air speed 0.06-0.07 m/sec, water temperature 28.4-28.6°C, pH 6.9-7.3, nitrates 0.7-1.1 mg/l, isocyanic acid <20 mg/l, turbidity 0.1-0.6 mg/l, suspended solids <1 mg/l and residual free chlorine 0.81-2.59 mg/l. Maximum number of users per hour 60-100, total daily users 220-240 persons. Pool 3: pool volume 700 m3 plus compensation tanks 60 m3 disinfectant sodium dichloro-S-triazine-trione (Dichloro 63), air intake 40,000 m3/h without circulation. The plant was monitored twice in 2007-2008. On sam- pling days, mean relative humidity was 70-75%, mean air temperature 24.5-25.5°C, mean air speed 0.03-0.05 m/sec. Water temperature in adult pool 29-30°C, pH 6.9, nitrates 14 mg/l, isocyanic acid 20 mg/l, turbidity 0.3 mg/l, suspended solids < 1 mg/l, vinyl chloride 5-8 µg/l and residual free chlorine 0.8-1.5 mg/l. Total number of users per day 250-300. Pool 4: pool volume 400 m3 plus compensation tank 24 m3, disinfectant sodium dichloro-S-triazine-trione and sodium hypochlorite, air input not available, turnover about 30%. The plant was monitored twice in 2007-2008. On sampling days, mean relative humidity was 83-84%, mean air temperature 24°C, mean air speed 0.05 m/sec, water temperature 29-30°C, pH 7.5, nitrates 11.6 mg/l, isocyanic acid 25 mg/l, turbidity 0.5 mg/l, suspended solids < 1 mg/l, vinyl chloride 0.05-0.12 µg/l and resid- ual free chlorine 1.5-1.8 mg/l. Total number of users per day 200. 2.2. Study Population In the four bathing complexes, six lifeguards and four instructors were monitored: the former worked at the poolside and the latter in the water. Thirty-one bathers underwent biological monitoring (15 swimmers at dif- ferent levels of expertise, four competitive swimmers and 12 persons enrolled water gym sessions). All filled in a questionnaire about personal details, weight, height, smoking and drinking habits, occupation. This informa- tion was used in the statistical analysis of the results. Before enrolment in the study, all subjects gave their informed consent. 2.3. Personal and Environmental Air Sampling Personal air sampling during the work-shift was per- formed for poolside personnel by means of radial diffu- sion air samplers for chloroform assay (Radiello®). In the measurements conducted in 2008, parallel active sampling with carbon vials was carried out at a flow rate of 100 ml/min to determine chloroform, bromodichloro- methane, dibromochloromethane and bromoform. Dou- ble sampling was carried out to assay bromine com- pounds, for which the manufacturer of diffusion sam- plers does not provide equivalent rates. Fixed (environmental) sampling was carried out about 1.5 m from the pavement at the edge of the pools (3 or 4 samples per bathing complex per day), in the changing rooms, offices and passages between the changing rooms and the pool. Sampling lasting 24 h was carried out with diffusion samplers (Radiello®) and others lasting about 9 h (when the pool was in use) were done using active carbon vials at an air flow of 100 ml/min. The same contaminants as for personal samples were assayed. In Pool 3, the 9-h sampling was divided into two periods of 4.5 h (morning and afternnon) in order to detect any changes in concentrations of the contaminants in the various areas. In this case the data was used as such and after calculation of the weighted mean concentration over the whole period the pool was open. For the analytical determination, samples were added with carbon disulfide containing deuterated benzene as internal standard and left in contact with the solvent for 30 min. The extract was injected in the GC/MS appara- tus (EI-SIM electronic impact, single ion monitoring). The analytical limit of detection (LOD) was 0.1 µg/ sample. 2.4. Estimation of Absorption of Chloroform Absorption of chloroform was estimated for staff and bathers, summing the fractions derived from direct in- gestion of water, inhalation of aerosols and vapours, and transcutaneous absorption. For absorption by ingestion, the results of Evans et al. 2001 [7] were used. According to the latter, water intake averages 22 ml/h for men 12 ml/h for women. Knowing the concentration of chloro- form in pool water, it was possible to calculate the quan- tity ingested, assuming 100% absorption. The fraction derived from ingestion was assumed to be zero for pool- side staff.
M. C. Aprea et al. / Natural Science 2 (2010) 68-78 Copyright © 2010 SciRes. OPEN ACCESS 71 The fraction derived from inhalation was estimated on the basis of time spent in the water, lung ventilation and median concentration of airborne contaminant at the poolside, corrected by a factor of 1.8 because the meas- urements were made 1.5 m from the pavement instead of 20 cm from the water’s surface [11]. A lung retention of 59% was assumed, as proposed by Kuo et al. [37]. Lung ventilation was assumed to be 15 l/min for males and 12 l/min for females for tasks involving little exertion (life- guard) and 30 l/min for males and 25 l/min for females for activity in the water. For poolside personnel, the concen- tration found by personal air sampling was used. The fraction derived from skin absorption was esti- mated on the basis of time spent in the water, chloroform concentration in pool water, body surface area estimated on the basis of weight and height using the Du Bois formula [38] and 80% contact of the skin with water. The permeation constant of skin was assumed to be 0.2 cm/h as proposed by Kuo et al. [37]. The fraction de- rived from skin absorption was assumed to be zero for poolside personnel. 2.5. Urine Sampling Spot samples of urine were obtained from personnel and bathers before and after exposure. Chloroform, bro- modichloromethane, dibromochloromethane and bro- moform were determined in all samples. The determina- tion was performed analyzing the head space in GC/MS EI-SIM using deuterated benzene as internal standard. The LOD was 0.050 µg/l. The data, expressed in µg/l was used as such and as dif- ferences between concentrations before and after exposure. 2.6. Statistical Analysis Statistical analysis was done using Stat View 5.0, Power PC Version (SAS Institute Inc.). Values below the ana- lytical limit of detection (LOD) were analyzed as half the LOD when at least half the data was over the LOD. Values above LOD but not quantifiable (<LOQ) were analyzed as the mean of LOD and LOQ. Parametric tests were used (analysis of variance, regression analysis, Student’s t test for paired and unpaired data) and the level of significance chosen was ά = 0.05. 3. RESULTS Concentrations of trihalomethanes in pool water on sampling days are shown in Table 1. Concentrations of contaminants in the water depended on the type of dis- infectants used, on any impurities in the water used to fill the pool and on water characteristics. Brominated compounds seemed to be associated more with use of sodium hypochlorite than with compounds such as cal- cium hypochlorite or Dichloro 63, irrespective of isocy- anates. Chloroform was confirmed to be the most abun- dant trihalomethane, and was only equal in concentration to bromodichloromethane and dibromochloromethane in pool 2, disinfected with sodium hypochlorite alone. Table 1. Concentrations of trihalomethanes (µg/l) in water of four public pools. Chloroform BDCM DBCM Bromoform Pool 1 N N < LOD Mean ± SD Median GM Min-Max 5 0 85.54±35.73 83.20 75.47 35.7-127.00 3 0 1.87±0.23 2.00 1.86 1.60-2.01 3 3 - - - - 3 3 - - - - Pool 2 N N < LOD Mean ± SD Median GM Min-Max 3 0 12.33±2.10 12.40 12.21 10.2-14.4 3 0 17.73±1.56 17.90 17.69 16.1-19.2 3 0 17.67±2.61 17.40 17.54 15.2-20.4 3 0 4.60±1.13 4.0 4.52 3.90-5.90 Pool 3 N N < LOD Mean ± SD Median GM Min-Max 6 0 33.23±9.72 38.40 31.83 19.00-40.80 6 1 1.48±0.61 1.70 1.25 0.25-1.80 6 0 0.63±0.09 0.61 0.62 0.52-0.78 6 0 0.04±0.004 0.040 0.042 0.40-0.50 Pool 4 N N < LOD Mean ± SD Median GM Min-Max 6 0 11.98±0.80 11.70 11.96 11.10-13.10 6 0 3.10±0.14 3.10 3.10 2.90-3.30 6 0 1.47±0.05 1.50 1.47 1.40-1.50 6 0 0.17±0.02 0.18 0.17 0.13-0.19 BDCM= Bromodichloromethane. DBCM= Dibromochloromethane. GM = geometric mean.
M. C. Aprea et al. / Natural Science 2 (2010) 68-78 Copyright © 2010 SciRes. OPEN ACCESS 72 Table 2. Descriptive statistics of concentrations of chloroform (µg/m3) detected in environmental air samples in four public pools. TOTAL DATA Poolside Change rooms and offices Passageways 9 h (a) 24 h (b) 9 h (a) 24 h (b) 9 h (a) 24 h (b) N 26 40 15 23 3 5 N <LOD 0 0 7 2 1 0 Mean ± SD 85±50 52±30 11±12 8±7 34±29 25±9 Median 65 46 4 5 50 20 GM 70 43 5 6 14 24 Min-Max 21-182 12-127 1-34 1-29 1-52 18-36 POOL 1 Poolside Change rooms and offices Passageways 9 h (a) 24 h (b) 9 h (a) 24 h (b) 9 h (a) 24 h (b) N 9 15 3 5 3 5 N <LOD 0 0 1 0 1 0 Mean ± SD 124±41 81±24 14±11 7±3 34±29 25±9 Median 128 78 18 6 50 20 GM 118 77 7 6 14 24 Min-Max 66-182 39-127 1-22 3-10 1-52 18-36 POOL 2 Poolside Change rooms and offices Passageways 9 h (a) 24 h (b) 9 h (a) 24 h (b) 9 h (a) 24 h (b) N 9 9 6 6 0 0 N <LOD 0 0 3 0 - - Mean ± SD 35±15 25±10 5±6 5±1 - - Median 32 23 2 5 - - GM 33 23 3 5 - - Min-Max 21-62 12-39 1-14 4-7 - - POOL 3 Poolside Change rooms and offices Passageways 9 h (a) 24 h (b) 9 h (a) 24 h (b) 9 h (a) 24 h (b) N 4 8 3 6 0 0 N <LOD 0 0 0 0 - - Mean ± SD 132±11 56±14 29±4 18±8 - - Median 130 53 27 16 - - GM 131 55 29 17 - - Min-Max 120-147 39-76 26-34 11-29 - - POOL 4 Poolside Change rooms and offices Passageways 9 h (a) 24 h (b) 9 h (a) 24 h (b) 9 h (a) 24 h (b) 9 ore (a) 24 ore (b) 9 ore (a) 24 ore (b) 9 ore (a) 24 ore (b) N 4 8 3 6 0 0 N <LOD 0 0 3 2 - - Mean ± SD 61±4 26±12 - 4±4 - - Median 63 26 - 3 - - GM 61 24 - 2 - - Min-Max 55-64 14-40 - 1-10 - - (a) Sampling conducted for 9 h in the presence of bathers; (b) Sampling conducted for 24 h in the presence and absence of bathers. Chloroform concentration detected in environmental samples are summarized in Table 2, where the poolside, change room, office and passageway data is presented separately. The table also shows 9-h and 24-h sampling data separately. The sampling site and bathing complex significantly affected chloroform concentrations when the pools were open and over 24 h. For 9-h sampling, the model explained 76% of the variance, with bathing complex explaining 31% and sampling site 45%, whereas for 24-h sampling the cor- responding percentages were 70%, 28% and 42%. Twenty-four-hour values were less than those measured when the pools were open, especially at the poolside, indicating that movement of the water increased airborne
M. C. Aprea et al. / Natural Science 2 (2010) 68-78 Copyright © 2010 SciRes. OPEN ACCESS 73 Figure 2. Concentrations of chloroform in morning, after- noon and 24-h environmemtal samples at pool 3. chloroform. Confirming this, Figure 2 shows chloroform concen- trations found in environmental samples at pool 3: sam- pling when the pool was open in the morning and after noon gave values much higher than 24-h data at the poolside, whereas those obtained in changing rooms and offices did not vary. Chloroform concentrations measured at the poolside when the pool was in use showed a statistically signifi- cant correlation (p<0.0001) with chloroform concentra- tions in the water and with the number of pool users per day (N). Multiple regression analysis showed that 74% of the variance was explained according to the following Equation: CHCl3 air (µg/m3) = -101.6 + 1.70 CHCl3 water (µg/l) + 0.57 N Temperature did not contribute significantly to the re- gression. Chloroform concentrations in personal air samples in the three bathing complexes where they were obtained are summarized in Table 3. As expected, they were lower than at the poolside because these personnel did not spend the whole shift beside the pools but also spent time in offices etc. where airborne concentrations of the contaminant were often less. With regard to airborne concentrations of brominated compounds, bromoform was never detected whereas bromdichloromethane (BDCM) and dibromochloro- methane (DBCM) were only detectable in poolside sam- ples of pools 2 and 4, where significant concentrations of the same contaminants were also found in the water (Table 4). The amount of data was therefore insufficient for multiple regression analysis between airborne and water concentrations. However, it can be said that the chemicophysical characteristics of contaminants strongly affect dispersal dynamics. In other words, for a given water concentration, chloroform passes much more read- ily into the vapour phase (vapour pressure 21.2 kPa at 20°C) than bromodichloromethane (vapour pressure 6.6 kPa at 20°C) and other brominated compounds that have even lower vapour pressures. Concentrations of BDCM, DBCM and bromoform were undetectable in all urine samples. Descriptive sta- tistics of chloroform concentrations detected in urine before and after exposure are summarized in Table 5 which also shows differences in concentration (delta) between the two times. The data is separated for persons carrying on activity in the water, for whom inhalation, ingestion and cutaneous absorption are likely, and per- sonnel working out of the water, for whom only respira- tory exposure is likely. A quick look at Table 5 shows that delta after/before was higher for subjects carrying on activity in the water, confirming the hypothesis of skin and digestive absorp- tion. In Table 6, the difference in concentrations af- ter/before exposure is shown in a differentiated manner depending on the type of activity and/or the pool fre- quented. Despite the small number of data items avail- able the table shows that for a given activity, delta af- ter/before depended on the bathing complex and there- fore on water and airborne concentrations of this con- taminant. Table 3. Descriptive statistics of concentrations of chloroform (µg/m3) detected in personal air samples. TOTAL DATA POOL 1 POOL 3 POOL 4 N 17 8 6 3 N<LOD 0 0 0 0 Mean ± SD 68±35 89±35 61±17 25±10 Median 61 95 61 20 GM 58 82 59 23 Min-Max 18-138 37-138 34-84 18-36 Table 4. Descriptive statistics of concentrations di bromodichloromethane (BDCM) and dibromochloromethane (DBCM) (µg/m3) detected in poolside air samples of the two pools in which at least 50% of the data was detectable. POOL 2 POOL 4 BDCM DBCM BDCM DBCM N 9 9 4 4 N<LOD 2 3 0 4 Mean ± SD 16±10 8±6 10±3 - Median 18 8 9 - GM 10 5 9 - Min-Max 1-27 1-17 7-13 -
M. C. Aprea et al. / Natural Science 2 (2010) 68-78 Copyright © 2010 SciRes. OPEN ACCESS 74 Table 5. Descriptive statistics of concentrations of chloroform (µg/l) detected in urine. Type of exposure (a) Start of exposure (before) End of exposure (after) Delta after/before N In water Out of water 35 6 35 6 35 6 N<LOD In water Out of water 11 1 0 0 - - Mean ± SD In water Out of water 0.262±0.351 0.265±0.236 0.659±0.667 0.563±0.627 0.397±0.455 0.297±0.480 Median In water Out of water 0.100 0.189 0.420 0.329 0.208 0.091 GM In water Out of water 0.123 0.165 0.404 0.342 - 0.141 Min-Max In water Out of water 0.025-1.676 0.025-0.615 0.025-3.327 0.100-1.746 0-2.227 0.052-1.271 (a) Exposure in water: swimmers, competitive swimmers, water gym participants, instructors; Exposure out of water: lifeguards and attendants. Table 6. Differences between concentrations at the end and start of exposure (µg/l) detected in urine during activity in and out of the water by pool and specific activity. N Mean ± SD Median GM Min-Max Competitive swimming (a) 4 0.065±0.047 0.074 - 0-0.113 Total swimmers Pool 1 Pool 4 15 9 6 0.506±0.585 0.768±0.635 0.112±0.077 0.250 0.672 0.107 - 0.490 - 0-2.227 0.025-2.227 0-0.207 Water gym course Pool 3 Pool 4 12 8 4 0.311±0.326 0.231±0.154 0.472±0.554 0.204 0.186 0.223 - - 0.309 0-1.301 0-0.426 0.142-1.301 Instructor Pool 1 Pool 3 4 3 1 0.580±0.225 0.637±0.238 - 0.511 0.609 - 0.550 0.607 - 0.408-0.887 0.414-0.887 0.408 Lifeguard/attendant Pool 1 Pool 3 Pool 4 3 2 1 0.529±0.645 - - 0.209 - - 0.305 - - 0.107-1.271 0.052-0.071 0.075 (a) only pool 3. Table 7. Absorbed chloroform (µg) estimated on the basis of concentrations in water and in poolside air while the pool was open. N Mean ± SD Median GM Min-Max Total doses 41 358.9±301.9 173.6 267.2 109.4-1248.4 Doses ingested 35 1.4±1.8 0.35 0.66 0.12-5.82 Transcutaneous doses 35 194.6±217.5 85.5 108.4 25.4-844.0 Respiratory doses 41 191.5±132.3 160.1 158.7 89.9-716.7 % ingested dose 35 0.3±0.2 0.2 0.2 0.1-0.7 % cutaneous dose 35 42.5±17.1 45.7 39.2 17.1-78.6 % respiratory dose 35 57.2±17.2 54.1 54.3 17.2-77.9 Table 7 shows estimated absorbed doses of chloro- form and the percentages of the total constituted by di- gestive, skin and inhalatory doses. Our estimates pro- duced absorption values up to about 1.25 mg for swim- mers or instructors in the water for long periods (2-3 h). For those carrying on activity in the water, the ingested percentage of the total dose was negligible compared to respiratory and skin doses that were 57% and 43%, re- spectively. Estimates of absorbed dose were analysed by linear regression model with chloroform delta after/before ex- posure and urinary concentrations of chloroform at the end of exposure. The results are shown in Figures 3 and 4. Both regressions were highly significant and the vari- ance explained by the model was 53% and 71%. The intercept with the ordinate was very close to zero in Fig- ure 3, as expected, and at 0.084 mg/l in Figure 4. In the latter case, the intercept should indicate the urinary con- centration of chloroform not due to time spent in the pool (pre-exposure value) and indeed it was close to the median for urinary chloroform at the beginning of ex- posure for subjects carrying on activity in the water, shown in Table 5 (this data was also the most numerous). The better correlation obtained in Figure 4 between
M. C. Aprea et al. / Natural Science 2 (2010) 68-78 Copyright © 2010 SciRes. OPEN ACCESS 75 Figure 3. Linear regression analysis between estimated ab- sorbed doses and delta chloroform after/before exposure (y = 0.00069 x +0.0004, r2 = 0.534, significant p<0.0001). Figure 4. Linear regression analysis between estimated ab- sorbed doses and chloroform concentrations in urine at the end of exposure (y = 0.0011 x + 0.084, r2 = 0.706, significant p<0.0001). estimated absorbed dose of chloroform and urinary ex- cretion of chloroform at the end of exposure with respect to the delta for chloroform can probably be ascribed to the further factor of variability due in the second case to the pre-exposure value of chloroform. The slope of the two regressions was very low, probably due to the fact that chloroform eliminated in urine at the end of expo- sure is only a limited part of the total absorbed, whereas a greater fraction is presumably eliminated by exhalation and stored in body fat. 4. DISCUSSION Concentrations of trihalomethanes reported in pool water vary from study to study but the results are not dissimilar to ours: Sandel [12] examined data from 114 home pools in the USA, obtaining a mean concentration of chloro- form of 67.1 μg/l and a maximum of 313 μg/l. Most other available data on trihalomethanes in pool water is summarized in Table 8. In the pools monitored by us, formation of brominated trihalomethanes seemed preva- lently associated with the use of sodium hypochlorite for water treatment. Ignoring bromide ions in the water used to fill these pools (town water in the case of pools 3 and 4), the presence of these compounds is presumably due to bromide impurities in the treatment reagents. This evidence makes it important to use only high purity re- agents to treat town water. Water-air transport of trihalomethanes depends on a number of factors that include concentrations in pool water, temperature and water disturbance and splashing by bathers. In our study, the concentration of chloroform detected at the poolside showed a good correlation with chloroform concentrations in pool water and with the number of swimmers present. Air and water tempera- tures were excluded from the regression model because they did not seem to have a significant effect on envi- ronmental concentrations of chloroform. Trihalomethane concentrations at different levels in the air above the pool should also depend on factors such as ventilation, size of pool building and air circulation. Most of the data available on concentrations of trihalomethanes in air above the pools is summarized in Table 9, which shows that measurements taken 20 cm above the water were on average 1.8 times higher than those taken 150 cm above the water. In our study, concentrations of airborne trihalome- thanes depended on where the measurements were taken (poolside, change rooms and offices, corridors) as found in other studies: Fantuzzi et al. [34] studied total triha- lomethane concentrations in five Italian indoor pools, finding mean concentrations in poolside air of 58.0 ± 22.1 μg/m3 and 26.1 ± 24.3 μg/ m3 at the reception. Absorption of trihalomethanes during time spent at the pool was investigated by comparing urinary excre- tion of chloroform before and after exposure. Levels observed at the start of exposure were slightly less than detected in the general population. A study conducted in Italy in 1994 [39] found median concentrations of 194 ng/l in the rural population (115 subjects) and 490 ng/l in the urban population (87 subjects). Most previous stud- ies on absorption of trihalomethanes at swimming pools measured blood concentrations of chloroform or those in alveolar air. Strähle et al. [35] compared concentrations
M. C. Aprea et al. / Natural Science 2 (2010) 68-78 Copyright © 2010 SciRes. OPEN ACCESS 76 of trihalomethanes in blood of swimmers with those in pool water and air. The results, summarized in Table 10, demonstrate that inhalation is probably the main route of absorption of volatile components, since concentrations in water of indoor pools are greater than those of outdoor pools, while concentrations in ambient air are higher indoors, as are blood concentrations. Good ventilation of pool premises should therefore significantly reduce ex- posure. Erdinger et al. [29] confirmed that exposure is prevalently respiratory, showing a ratio of 3:1 with re- spect to skin absorption. Aggazzotti et al. [14-16,36] showed that exposure in chlorinated pools can cause an increase in trihalomethane concentrations in plasma and alveolar air, but the latter declines soon after leaving the pool. Plasma concentrations of chloroform were detect- able in 100% of the 127 samples analyzed, showing a mean concentration of 1.06 µg/l, whereas BDCM, de- tectable in only 25 samples, showed a mean of 0.14 μg/l and DBCM, detectable in only 17 samples, showed a mean of 0.1 μg/l. Table 8. Concentrations of trihalomethanes in pool water (µg/l). Chloroform BDCM DBCM Bromoform country Mean Range Mean Range Mean Range Mean Range Type of poolRef. Poland 35.9-99.7 2.3-14.7 0.2-0.8 0.2-203.2 Indoor [13] 19-94 [14] 93.7 9-179 [15] Italy 33.7 25-43 2.3 1.8-2.8 0.8 0.5-10 0.1 0.1 Indoor [16] 37.9 Indoor [17] 4-402 1-72 <0.1-8 <0.1-1 Outdoor USA 3-580 1-90 0.3-30 <0.1-60 Indoor [18] 14.6 2.4-29.8 Indoor 43 14.6-111 Outdoor [19] 198 43-980 22.6 0.1-150 10.9 0.1-140 1.8 0.1-88 Indoor [20] 0.5-23.6 1.9-16.5 <0.1-3.4 <0.1-3.3 Indoor 3.6-82.1 1.6-17.3 <0.1-15.1 <0.1-4.0 Outdoor [21] 94.9 40.6-117.5 4.8 4.2-5.4 1.8 0.78-2.6 Indoor [22] 80.7 8.9 1.5 <0.1 Indoor Germany 74.9 11.0 3.0 0.23 Outdoor [23] 3-27.8 Indoor [24] 1.8-28 Indoor [11] 8-11 Indoor [25] 14 0.51-69 2.5 0.12-15 0.59 0.03-4.9 0.16 <0.03-8.1 Indoor 30 0.69-114 4.5 0.27-25 1.1 0.04-8.8 0.28 <0.03-3.4 Outdoor [26,27] 3.8 6.4 max Indoor [28] Germany 7.1-24.8 Indoor [29] Denmark 145-151 Indoor [30] Hungary 11.4 <2-62.3 2.9 <1-11.4 Indoor [31] UK 121.1 45-212 8.3 2.5-23 2.7 0.67-7 0.9 0.67-2 Indoor [32] Table 9. Concentrations of trihalomethanes in air above the pool surface (µg/m3). Chloroform BDCM DBCM Bromoform country Mean Range Mean Range Mean Range Mean Range Type of poolRef. 214 66-650 19.5 5-100 6.6 0.1-14 0.2 [15] 140 49-280 17.4 2-58 13.3 4-30 0.2 [14] Italy 169 35-195 20 16-24 11.4 9-14 0.2 Indoor (a) [16] Canada 597-1630 Indoor [33] 65 9.2 Indoor (a) 36 5.6 3.8 Indoor (b) 5.6 0.21 1.2 Outdoor (a) 2.3 Outdoor (a) [11] 3.3 0.33-9.7 0.4 0.08-2.0 0.1 0.02-0.5 <0.03 Outdoor (a) 1.2 0.36-2.2 0.1 0.03-0.16 0.05 0.03-0.08 <0.03 Outdoor (b) 39 5.6-206 4.9 0.85-16 0.9 0.05-3.2 0.1 <0.03-3.0 Indoor (a) Germany 30 1.7-136 4.1 0.23-13 0.8 0.05-2.9 0.08 <0.03-0.7 Indoor (a) [26,27] <0.1-1 <0.1 <0.1 <0.1 Indoor (c) USA <0.1-260 <0.1-10 <0.1-5 <0.1-14 Outdoor (c)[18] (a) 20 cm above water surface; (b) 150 cm above water surface; (c) 200 cm above water surface.
M. C. Aprea et al. / Natural Science 2 (2010) 68-78 Copyright © 2010 SciRes. OPEN ACCESS 77 Table 10. Comparison of concentrations of trihalomethanes (THM) in blood of swimmers after 1 h of exercise, in pool water and in ambient air of indoor and outdoor pools [35]. THM (mean - range) indoor pools outdoor pools Blood of swimmers (μg/l) 0. 48(0.23-0.88) 0.11(<0.06-0.21 Pool water (μg/l) 19.6(4.5-45.8) 73.1(3.2-146) air 20 cm above water surface (μg/m3) 93.6(23.9-179.9) 8.2(2.1-13.9) air 150 cm above water surface (μg/m3) 61.6(13.4-147.1) 2.5(<0.7-4.7) Absorptions estimated by us confirmed that the quan- tity of chloroform taken up by inhalation was a major portion of the total dose for bathers and instructors, be- ing 57% compared to 43% absorbed through the skin. These estimates are based on the results of other studies in the literature, from which we obtained lung retention and skin penetration. They are undoubtedly associated with errors because respiratory dose is greatly affected by lung ventilation which was assumed by us without any precise indications about the real volume of air in- haled and without considering differences between sub- jects due to physical exertion and age. As far as we are aware, no similar estimates have been reported in the literature and therefore our data forms an excellent basis for further research, including epidemiological studies. The data should be implemented in this way to make it more representative. The good correlation observed with urinary concentrations at the end of exposure and with delta after/before exposure confirms that even if our es- timates were not quantitatively exact, they are highly indicative of exposure. 5. CONCLUSIONS This study shows that concentration of trihalomethanes in pool water vary as a consequence of the type of disin- fectants used and of the impurities in the treatment re- agents. Trihalomethanes are lost from the surface of the water and are found in the air above the pool. Water-air transport depends on a number of factors that include concentrations in pool water, temperature and water dis- turbance by bathers. The sampling site and bathing com- plex significantly affect air concentrations. Absorption of trihalomethanes for workers and swimmers, during time spent at the pool, evaluated by urinary excretion of the same compounds before and after exposure, is higher for subjects carrying on activity in the water, confirming the importance of skin and digestive absorption, al- though inhalation is on average the major portion of the total absorbed dose. The results show that even “healthy” places like pools can pose chemical agent management problems that are far from simple. 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