The water of swimming pools is subjected to disinfection for inactivating microbial pathogens and preventing waterborne diseases (Ilyas et al., 2018). Among the four main classes of disinfectants (chlorine-based, bromine-based, ozone, and UV), chlorine is the most commonly used for indoor swimming pools (Teo et al., 2015; Wyczarska-Kokot et al., 2020). However, unintended reactions between chlorine and natural organic matter present in water lead to the formation of disinfection byproducts, including chloramines (Chowdhury et al., 2016; Teo et al., 2016). Trichloramine (TCA) has the highest concentration among other volatiles in indoor swimming pool air (Weng et al., 2011; Yang et al., 2018). More specifically, due to the high volatility (vapour pressure =19.95 kPa at 20°C) and relatively low water solubility of trichloramine compared to monochloramine and dichloramines, trichloramine disperses mainly in the gaseous phase (Manasfi et al., 2017). Therefore, to assess air contamination in indoor swimming pools and occupational exposure to chloramines, trichloramine is the most used representative due to its high volatility and relatively low water solubility (Ratnayaka et al., 2009).
A high number of reported health issues showed that swimming pool facilities with a high prevalence of airway irritation could be explained by high TCA exposure levels (Fantuzzi et al., 2012; Parrat et al., 2012; Lévesque et al., 2015). In this context, Hery et al. (1995) were the first to find an association between airborne TCA levels and acute respiratory symptoms among swimming pool instructors (Hery et al., 1995). Further studies reported TCA to cause ocular and respiratory symptoms in swimming pool employees (Massin et al., 1998; Jacobs et al., 2007; Chen et al., 2008; Fantuzzi et al., 2010; Nordberg et al., 2012). In a study of 41 indoor swimming pools in Quebec (Canada), Tardif et al. (2016) reported median concentrations of 0.23 mg/m3, with the highest concentration being 0.56 mg/m3 (Tardif et al., 2016). Other studies reported concentrations of TCA ranging from 0.1 mg/m3 to 2.2 mg/m3 (Richardson et al., 2010; Carter and Joll, 2017; Manasfi et al., 2017). For workers’ protection, the airborne TCA recommendation levels vary between 0.2 mg/m3 (German Working Group on Indoor Guide Values of the Federal Environment Agency, 2011) to 0.5 mg/m3 (ANSES, 2010). Only British Columbia offered an exposure limit concentration of 0.35 mg/m3 (Westerlund et al., 2019) for an 8-hour exposure limit in Canada.
No standard sampling and analysis methods have been published for TCA by mandatory organizations such as OSHA (Occupational Safety and Health Administration), US EPA (United States Environmental Protection Agency), and NIOSH (National Institute for Occupational Safety and Health). However, reported data from environmental sampling using Hery’s method has been used to determine occupational exposures (Saleem et al., 2019; Westerlund et al., 2019). Hery’s analytical and sampling method consists of pumping air at a 1 L/min flow rate for 2 hours through a sampling cassette made up of a Teflon prefilter (Polytetrafluoroethylene) and two quartz fibre filters (QFFs) impregnated with sodium carbonate and arsenic trioxide. In the presence of sodium bicarbonate, chloramines are decomposed into ammonia and hypochlorite, and in the presence of arsenic trioxide, hypochlorite ions are then reduced to chlorides. These chlorides are then quantified by ion chromatography. Any other chloride (mono and dichloramine) which could be present in the air (in the form of droplets) should be eliminated by the prefilter while the TCA passes through the prefilter and then gets trapped on QFFs. However, Hery et al. (1995) indicated that a potential transfer of chlorides from the Teflon prefilter to the QFFs due to quick vaporization and adsorption could occur (Hery et al., 1995).
The past thirty years have seen rapid advances in TCA exposure assessment, and several studies assessed TCA levels in indoor swimming pools using different sampling strategies(Soltermann et al., 2014; Zwiener and Schmalz, 2015; Wu et al., 2021). Modified Hery methods have been reported using different sampling pump flow rates and types of prefilters. While some studies did not use prefilters (Massin et al., 1998; Person et al., 2005; Westerlund, 2016; Westerlund et al., 2019), others replaced the Teflon prefilter with Glass fibre filters (Lévesque et al., 2015). In addition, different flow rates from 0.25 L/min (Westerlund, 2016) to 4 L/min (Person et al., 2005) were used for sampling. For instance, some authors used low flow rates to avoid the rapid passage of TCA through the QFFs, which could result in a loss of TCA adsorption on QFFs and consequently an underestimation of TCA concentrations (Drolet and Beauchamp, 2012; NIOSH, 2017). Sampling parameters (e.g., prefilter and flow rate) used in the different published studies are reported in Table 1. To the best of our knowledge, no study has assessed the impact of modifying these parameters (using a prefilter or not, changing the flow rate) on the reported TCA concentrations using an experimental set-up and field sampling.
This study presents a comparison of different sample collection approaches for measuring TCA in the air of indoor swimming pools. More specifically, this study aims to assess the effect of TCA concentrations, the prefilter (cassette assembly) and the sampling flow rate on the TCA measurements.
Table 1
Descriptive results and methods and reported TCA Concentrations in the air of indoor swimming pools.
References
|
Sample numbers
|
TCA Concentration (mg/m3)
|
Prefilter type
|
Flow rate (L/min)
|
Range
|
Mean
|
(Hery et al., 1995)
|
675
|
≤0.05 - 1.92
|
0.42
|
Teflon
|
1
|
(Massin et al., 1998)
|
1262
|
0.07 - 0.41
|
0.24
|
--
|
1
|
(Person et al., 2005)
|
35
|
0.08 - 0.6
|
0.23
|
--
|
4
|
(Jacobs et al., 2007)
|
120
|
0.17 - 1.34
|
0.56
|
Teflon
|
1.2
|
(Richardson et al., 2010)
|
6
|
0.17 - 0.43
|
0.29
|
Teflon
|
1.2
|
(Catto et al., 2012)
|
19
|
0.11 - 0.35
|
0.22
|
Teflon
|
1
|
(Lévesque et al., 2015)
|
26
|
0.11 - 0.70
|
0.38
|
Glass
|
1
|
(Westerlund, 2016)
|
110
|
<0.001-0.64
|
0.18
|
--
|
0.25
|
(Tardif et al., 2016)
|
40
|
≤0.05 - 0.56
|
0.23
|
Teflon
|
1
|
(Lofstedt et al., 2016)
|
52
|
<0.001-0.24
|
0.07
|
--
|
0.25
|
(Saleem et al., 2019)
|
28
|
0.06 - 0.22
|
0.14
|
Teflon
|
1
|
(Tsamba et al., 2020)
|
50
|
0.02 - 0.45
|
0.05
|
--
|
0.5
|