Utilize este identificador para referenciar este registo: http://hdl.handle.net/10400.18/754
Título: Trihalomethanes in Lisbon Indoor Swimming Pools: Occurrence and Determining Factors
Autor: Silva, Z.
Rebelo, H.
Silva, M.M.
Alves, A.
Cabral, C.
Almeida, A.C.
Aguiar, F.
Oliveira, A.
Nogueira, A.
Pinhal, H.
Matos, A.
Ramos, C.D.
Pacheco, P.
Aguiar, P.
Cardoso, A.S.
Palavras-chave: Indoor Swimming Pools
Water and Air Quality
Distribution and Determinants
Correlations Between variables
Água e Solo
Data: Mar-2011
Editora: Instituto Nacional de Saúde Doutor Ricardo Jorge, IP
Resumo: The presence of water disinfection by-products (DBPs) in swimming pools constitutes today a public health concern, particularly because swimming is an activity used by a high percentage of the population, namely elderly and young children. Moreover, several adverse short-term and long-term health effects have been associated with these compounds (Lakind et al., 2010; Zwiener et al., 2007). Water disinfection methods are used in all swimming pools, namely in public pools, to ensure an adequate and effective protection of users against microbiological pathogens. Chlorination is the most common disinfection method used worldwide, because it is low cost, easy to use, efficient against a broad spectrum of microorganisms, and enables the maintenance of a residual protection. The use of chlorine based treatment techniques has one strong drawback, which is the generation of several DBPs, potentially harmful products, that can be absorbed by ingestion, inhalation and absorption through the skin (Nieuwenhuijsen et al., 2009; Caro and Gallego, 2007). DBPs comprise several compounds that are formed through the reaction of chlorine with organic matter present in water. Amongst DBPs, the most relevant and better characterized are trihalomethanes (THMs): chloroform (CF), bromoform (BF), bromodichloromethane (BDCM), and chlorodibromomethane (DBCM). These compounds have been associated with health effects such as respiratory, ocular and cutaneous symptoms and also with some long-term health effects such as bladder cancer and adverse reproductive outcomes (Lee et al., 2009; Zwiener et al., 2007). Accurate exposure assessments to THMs in indoor pool environment is particularly difficult because their formation depends on many factors such as water and air temperature (Tw and Tair), humidity (Hu), pH, free residual chlorine (FrCl), total organic content and number of pool users (Lee et al., 2009). In Portugal a specific legislation to assess the quality of swimming pool waters is inexistent. The guideline value used in this study for total THMs (TTHMs) was the one established in the Portuguese Law 306/2007, for drinking water quality - 100 μg/L. Some other water parameters determined in swimming pools such as Tw turbidity (Turb), pH, FrCl, total residual chlorine, conductivity (Cond), permanganate index (COD) and isocyanuric acid were assessed by Portuguese Law 5/97, regarding technical and safety conditions of closed environments with water diversions. WHO guidelines for safe recreational water environments (2006) were also used to assess some water and air parameters in pools. Standard 62.1 (2006) from American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASRHAE) was also used to assess pool air parameters. The main goal of this investigation project was to study the occurrence, distribution and determinants of THMs in indoor swimming pools. This will enable an evaluation of swimming pool users’ exposure to THMs. In order to achieve this goal, the characterization of water quality of 30 Lisbon indoor swimming pools, using chorine based treatment techniques, was made during a six month period. Because of laboratory working restrictions, CF concentration in pool air was studied only in 6 swimming pools, at the same period. Several parameters such as TTHMs concentration, CF, BDCM, DBCM, BF concentration in water, FrCl, combined residual chlorine (CrCl), pH, Tw and Tair, Hu, COD, Cond, Turb and chloride (Cl) were determined in each pool, once a month. THMs water sampling was made in duplicates in two pool water spots, physicochemical parameters were determined in one of the THMs water sampling spots and THMs air sampling was made in two pool spots, considered to be representative of the swimming pool air. All sampling procedures were performed by specialized sampling technicians from Lisbon Health Centres Group (ACES). Statistical analysis was performed using the SPSS 17.0 software. Descriptive analysis was applied to all variables in order to determine mean, median, standard deviation, minimum and maximum. Student’s t-test and Mann-Whitney tests were used to compare numerical variables and Spearman’s rank correlation coefficient were used to examine correlation between all environmental parameters. TTHMs water level ranged from 10 to 160 μg/L, while CF water level typically ranged from 5 to 150 μg/L, with occasional higher levels detected. Regarding other THMs levels in pool water, BDCM ranged from 0.5 to 15 μg/L, DBCM from 0.4 to 10 μg/L and BF was obtained in concentrations less than 2 μg/L. Moreover, in some pools, DBCM and BF were not detected. From these results, it can be concluded that there was a large variation in TTHMs and CF water levels between the pools and that CF was the THM obtained in higher concentrations. These results are in agreement with studies presented by other authors (Lee et al., 2009; Chu and Nieuwenhuijsen, 2002). In air, CF level ranged from 40 to 200 μg/m3, with occasional higher levels detected. Tw presented less variation (27 to 31 ºC) than Tair (21 to 33 ºC), although sporadic higher values were found. FrCl and Cond presented higher values than the guidelines from DR 5/97 only in a small number of pools. Turb and COD values were within the guidelines from DR 5/97. pH varied from 7 to 8.5, with only a small number of pools having values higher than 7.8. As referred in WHO guidelines, pH should be maintained between 7.2 and 7.8 for chlorine disinfectants to ensure efficient disinfection. Using the statistical tests mentioned before, it was possible to obtain some interesting results. There was a clear positive linear correlation between CF water concentration (CFW) and TTHMs water concentration (R>0.98, p<0.01), good correlation other THMs, there was a clear positive linear correlation between BDCM and DBCM water concentration (R>0.78, p<0.01) and good correlation between TTHMs water concentration and Tw (R>0.45, p<0.05). These results are in agreement with Lee et al. (2009) which obtained positive linear correlations between CFW and COD and with Chu and Nieuwenhuijsen (2002) which also obtained correlations between TTHMs water concentration and Tw. In conclusion, there appears to be good water and air quality in the studied Lisbon swimming pools. Regarding THMs levels in water, some pools presented high TTHMs and CF concentrations. Moreover, CF air concentrations were also high in some swimming pools. These results clearly demonstrate that THMs monitoring is particularly important and that, in a near future, this should be extended to other DBPs. Furthermore, for a correct and conscious use of swimming pools, appropriate and targeted information about safe practices should be provided to pool users.
Descrição: Inclui artigo publicado em: Proceedings of the 4th International Conference of Swimming Pool & SPA(ICOEH), 2011, Porto: 40-50
Peer review: yes
URI: http://hdl.handle.net/10400.18/754
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