The deplorable environmental conditions coupled to poor management practices employed by public swimming pool owners have led to suspicions over the safety of these recreational sites. This study was carried out to determine the physicochemical properties, heavy metal contents and accumulation, and associated risks of six swimming pools in Owerri, Capital of Imo State, Nigeria. Physicochemical analysis was conducted using standard methods while determination of heavy metals was carried out using an atomic absorption spectrophotometer. Results obtained showed that the turbidities and total dissolved solutes exceeded the Nigeria standard for water quality. Iron (Fe), cadmium (Cd), mercury (Hg), arsenic (As), nickel (Ni), and lead (Pb) exceeded the drinking safety values from United States Environmental Protection Agency, National Standards for Drinking Water Quality, and World Health Organization, while selenium (Se), chromium (Cr), and zinc (Zn) values fell within the permissible limits. From the bioaccumulation models applied, the enrichment factors showed anthropogenic source of deposition of the metals in all swimming pool while the heavy metal index were in a range of 27.30-70.19. For the risk assessment results, the chronic daily intake showed that Hg, and As levels for all the swimming pools, and Cu for some swimming pools exceeded the oral reference doses, while the hazard quotient for Hg (5.65-16.95), As (2.26-3.77), and Cu (1.13-4.11) indicated potentials of causing related toxicities. This study has shown that the aesthetic quality of the swimming pools were compromised, and contained elevated levels of Hg, As, and Cu significant enough to threaten the health safety of users of these swimming pools, which should instigate tough measures from Nigerian water regulatory bodies to ensure compliance from public swimming pool owners.
Water is one of the most important natural resources crucial in supporting life processes in both plants and animals [
The six swimming pools used for this study, were hotel swimming pools cut across major roads in the Metropolis including Okigwe road, Amakohia road, World Bank road, and Port Harcourt road. The test samples were obtained directly from the swimming pools just before washing and refilling of the pool by the management, while the control samples were obtained from the source of refilling.
The samples (20 mL) were collected during the rainy season (June, 2018). Triplicate surface water samples were collected from mid-depth portions of each of the swimming pools, as well as their corresponding control samples using sterilized sample bottles. On collection of the samples, the sample bottles were first rinsed thrice with the swimming pool water samples, and stabilized using hydrochloric acid after sample collection. The samples were immediately conveyed to the laboratory for analysis.
The temperature of the sample was measured by dipping a centigrade thermometer into the sample while the pH, electrical conductivity, and total dissolved solute (TDS) was measured using a HI 98129 portable pH/EC/TDS/temperature meter (Hanna Instrument, Inc. RI, USA). The alkalinity and dissolved oxygen contents were determined following instructions on HI3811 alkalinity test kit and HI3810 dissolved oxygen test kit (Hanna Instrument, Inc. RI, USA) while the turbidity was determined using a UV-VIS spectrophotometer at 860 nm. The heavy metals; iron (Fe), cadmium (Cd), Hg, As, nickel (Ni), selenium (Se), chromium (Cr), lead (Pb), zinc (Zn), and copper (Cu) were determined using an AA-670 atomic absorption spectrophotometer (Shimadzu Corporation. Kyoto, Japan). Briefly, the samples (20 mL) were digested using 15mL mixture of perchloric acid, sulfuric acid, and nitric acid, in a ratio of 1:1:5. The mixture was heated in a heating mantle at 80 ℃ until a clear solution was obtained and afterwards, cooled and made up to 30 mL with 2% nitric acid and filtered. The heavy metal contents were thus determined in the digested samples using an AA-670 atomic absorption spectrophotometer (Shimadzu Corporation. Kyoto, Japan) after the preparation of a reference solution [
The enrichment factor (EF) is expressed mathematically as;
where, Cn (mg/L) represents the concentration of the element n at the test site, while Ctn (mg/L) stands for the concentration of the element n at the control site [
To calculate the heavy metal index (HMI), the following mathematical relationship was applied;
where Sv represents the standard values. The standard values were obtained as mean and standard deviations of permissible levels of heavy metal set by United States Environmental Protection Agency (USEPA) [
The chronic daily intake via oral route (CDIing; mg/kg/day) was determined following the mathematical relationship below [
where IR (L/day) represents the ingestion rate, and EF (days/year) represents exposure frequency, ED (year) represents the exposure duration, BW (Kg) represents the body weight and AT (days) represents averaging time. Standard IR for adult swimmers is 21 mL/h. From the swimming pool management data, the average swim time per day (exposure time) is 5.4 h (i.e. 5.4 h/days). Thus, the calculated IR (mL/day) = 21×5.4=113.4 mL/day = 0.113 L/day.
EF was obtained from documentations of the six pool management and the average EF is represented below;
The BW was 70kg representing the average BW of an adult [
4 – 68 = 64 years ED for S.P1
5 – 61 = 56 years ED for S.P2
4 – 73 = 69 years ED for S.P3
4 – 64 = 60 years ED for S.P4
5 – 60 = 55 years ED for S.P5
4 – 61 = 57 years ED for S.P6
AT = EF x ED = 3226.72 days
The chronic daily intake via the dermal route (CDIderm; mg/kg/day) was calculated following the mathematical expression below;
Cn is the heavy metal concentration (mg/L), SA is the surface body area of an adult given as 18000 cm2 [
Hazard quotient (HQ) was calculated following the relationship below;
where RfD is reference doses obtained from USEPA [
The data obtained was presented as mean ± SD of triplicates. Analysis of the data was carried out using Statistical Package for Science and Social Sciences (SPSS) version 20, using one way analysis of variance (ANOVA) and the least standard deviations (LSD) at 95% confidence interval (CI; p < 0.05) considered as significant.
The turbidity of all the swimming pools shown in
This study has shown that the aesthetic quality of the swimming pools was compromised, and contained elevated levels of Hg, As, and Cu, which were significant enough to threaten the health safety of users of these swimming pools users. Thus, imminent strategies are required by the regulatory bodies to checkmate the safety processes applied by the management of these commercial swimming pools to prevent the heavy metal contamination, and enforce compliance to standard approaches. Also, this result raises serious concerns over the heavy metal pollution status of the metropolis at large, as well as the rationale behind situating commercial swimming pools in the heart of population dense cities without adequate protections put in place.
No conflict of interest declared.
Temperatures of swimming pools
* NSDWQ=Nigeria Standard for Drinking Water Quality
pH of swimming pools
* NSDWQ=Nigeria Standard for Drinking Water Quality
Turbidity of swimming pools
* NSDWQ=Nigeria Standard for Drinking Water Quality
Alkalinity of swimming pools
* WHO=World Health Organization
Total dissolved solute (TDS) of swimming pools
* NSDWQ=Nigeria Standard for Drinking Water Quality
Conductivity of swimming pools
* NSDWQ=Nigeria Standard for Drinking Water Quality
Dissolved oxygen of swimming pools
* MK= Manoj and Avinash [
Iron (Fe), cadmium (Cd), mercury (Hg), arsenic (As), and nickel (Ni) contents (mg/L) of swimming pools
Swimming pool | Fe | Cd | Hg | As | Ni |
---|---|---|---|---|---|
L1 | |||||
Test | 3.86±0.9a | 0.03±0.0a | 0.02±0.0a | 0.08±0.01a | 0.13±0.01a |
Control | 1.06±0.3b | BDL | BDL | 0.02±0.0b | 0.06±0.0b |
Standard | 0.20±0.1c | 0.003±0.0b | 0.001±0.0b | 0.01±0.0b | 0.02±0.0c |
L2 | |||||
Test | 4.19±1.31a | BDL | 0.03±0.0a | BDL | 0.09±0.03a |
Control | 0.71±0.2b | BDL | 0.01±0.0a | BDL | 0.03±0.0b |
Standard | 0.20±0.1c | 0.003±0.0 | 0.001±0.0c | 0.01±0.0 | 0.02±0.0b |
L3 | |||||
Test | 1.78±0.40a | 0.02±0.0a | BDL | 0.03±0.0a | 0.07±0.01a |
Control | 0.35±0.02b | 0.01±0.0a | BDL | 0.01±0.0b | 0.02±0.0b |
Standard | 0.20±0.1b | 0.003±0.0b | 0.001±0.0 | 0.01±0.0b | 0.02±0.0b |
L4 | |||||
Test | 3.45±0.77a | 0.01±0.0a | 0.01±0.0a | 0.05±0.02a | 0.03±0.0a |
Control | 1.21±0.31b | 0.01±0.0a | BDL | 0.02±0.0b | BDL |
Standard | 0.20±0.1c | 0.003±0.0b | 0.001±0.0b | 0.01±0.0b | 0.02±0.0a |
L5 | |||||
Test | 0.93±0.22a | 0.02±0.0a | BDL | BDL | 0.06±0.01a |
Control | 0.31±0.07b | BDL | BDL | BDL | 0.02±0.0b |
Standard | 0.20±0.1b | 0.003±0.0b | 0.001±0.0 | 0.01±0.0 | 0.02±0.0b |
L6 | |||||
Test | 0.51±0.13a | 0.03±0.0a | 0.01±0.0a | 0.06±0.02a | 0.05±0.02a |
Control | 0.41±0.11a | 0.01±0.0a | BDL | 0.01±0.0b | 0.03±0.0ab |
Standard | 0.20±0.1b | 0.003±0.0b | 0.001±0.0c | 0.01±0.0b | 0.02±0.0b |
* L1-L6 = Location 1-6.
* Values are means and standard deviations of triplicate determinations.
* For each swimming pool, values bearing dissimilar superscript letter (s). a, b down the column denote that the mean difference is significant at p<0.05. BDL = Below Detection Level.
Selenium (Se), chromium (Cr), lead (Pb), zinc (Zn), and copper (Cu) contents (mg/L) of swimming pools
Swimming pools | Se | Cr | Pb | Zn | Cu |
---|---|---|---|---|---|
L1 | |||||
Test | BDL | 0.05 ± 0.0a | 0.05 ± 0.01a | 0.63 ± 0.2a | 0.33 ± 0.08a |
Control | BDL | BDL | 0.02 ± 0.0b | 0.41 ± 0.1a | 0.08 ± 0.02b |
Standard | 0.03 ± 0.02 | 0.05 ± 0.0a | 0.01 ± 0.0b | 4.33 ± 1.2b | 1.33 ± 0.60c |
L2 | |||||
Test | BDL | 0.07 ± 0.01a | 0.09 ± 0.02a | 3.87 ± 1.01a | 0.50 ± 0.1a |
Control | BDL | 0.02 ± 0.0b | 0.02 ± 0.0b | 0.24 ± 0.06b | BDL |
Standard | 0.03 ± 0.02 | 0.05 ± 0.0a | 0.01 ± 0.0b | 4.33 ± 1.2a | 1.33 ± 0.60b |
L3 | |||||
Test | 0.02 ± 0.0a | 0.04 ± 0.0a | 0.08 ± 0.02a | 3.11 ± 0.92a | 0.21 ± 0.05a |
Control | BDL | 0.01 ± 0.0b | 0.04 ± 0.01b | 0.93 ± 0.14b | 0.20 ± 0.09a |
Standard | 0.03 ± 0.02a | 0.05 ± 0.0a | 0.01 ± 0.0c | 4.33 ± 1.2a | 1.33 ± 0.60b |
L4 | |||||
Test | 0.01 ± 0.0a | BDL | 0.05 ± 0.01a | 1.90 ± 0.50a | 1.82 ± 0.31a |
Control | BDL | BDL | 0.01 ± 0.0b | 1.04 ± 0.29b | 0.30 ± 0.05b |
Standard | 0.03 ± 0.02a | 0.05 ± 0.0 | 0.01 ± 0.0b | 4.33 ± 1.2c | 1.33 ± 0.60a |
L5 | |||||
Test | 0.03 ± 0.0a | 0.07 ± 0.02a | 0.09 ± 0.04a | 4.43 ± 0.88a | 0.74 ± 0.13a |
Control | 0.01 ± 0.0b | 0.01 ± 0.0b | 0.02 ± 0.0b | 1.21 ± 0.04b | BDL |
Standard | 0.03 ± 0.02a | 0.05 ± 0.0a | 0.01 ± 0.0b | 4.33 ± 1.2a | 1.33 ± 0.60c |
L6 | |||||
Test | 0.01 ± 0.0a | 0.04 ± 0.0a | 0.06 ± 0.02a | 2.75 ± 0.61a | 1.32 ± 0.38a |
Control | BDL | BDL | 0.04 ± 0.01a | 2.16 ± 0.93a | 0.29 ± 0.05b |
Standard | 0.03 ± 0.02a | 0.05 ± 0.0a | 0.01 ± 0.0b | 4.33 ± 1.2c | 1.33 ± 0.60a |
* L1-L6 = Location 1-6.
* Values are means and standard deviations of triplicate determinations.
* For each swimminng pool, values bearing dissimilar superscript letter(s) (a, b) down the column denote that the mean difference is significant at p < 0.05. BDL = Below Detection Level .
Enrichment factor (EF) of heavy metal depositions in swimming pools
Swimming pool | Fe | Cd | Hg | As | Ni | Se | Cr | Pb | Zn | Cu |
---|---|---|---|---|---|---|---|---|---|---|
L1 | 3.58 | - | - | 4.00 | 2.17 | - | - | 1.50 | 1.54 | 4.13 |
L2 | 5.90 | - | 3.00 | - | 3.00 | - | 3.50 | 4.50 | 16.13 | - |
L3 | 5.09 | 2.00 | - | 3.00 | 3.50 | - | 4.00 | 2.00 | 3.34 | 1.05 |
L4 | 2.85 | 1.00 | - | 2.50 | - | - | - | 5.00 | 1.83 | 6.06 |
L5 | 3.00 | - | - | - | 3.00 | 3.00 | 7.00 | 4.50 | 3.66 | - |
L6 | 1.24 | 3.00 | - | 6.00 | 1.67 | - | - | 1.50 | 1.27 | 4.55 |
* L1-L6 = Location 1-6.
* Iron (Fe). cadmium (Cd), mercury (Hg), arsenic (As), nickel (Ni), selenium (Se), chromium (Cr), lead (Pb), zinc (Zn), and copper (Cu).
Heavy metal index (HMI) of swimming pools
Swimming pools | Fe | Cd | Hg | As | Ni | Se | Cr | Pb | Zn | Cu | MI |
---|---|---|---|---|---|---|---|---|---|---|---|
L1 | 19.30 | 10.00 | 20.00 | 8.00 | 6.5 | - | 1.00 | 5.00 | 0.14 | 0.25 | 70.19 |
L2 | 20.95 | - | 30.00 | - | 4.5 | - | 2.33 | 9.00 | 0.89 | 0.38 | 68.05 |
L3 | 8.90 | 6.67 | - | 3.00 | 3.5 | 0.66 | 0.80 | 6.00 | 0.72 | 0.16 | 30.41 |
L4 | 17.25 | 3.33 | 10.00 | 5.00 | 1.5 | 0.33 | - | 5.00 | 0.44 | 1.37 | 44.22 |
L5 | 4.65 | 6.67 | - | - | 3.00 | 1.00 | 1.40 | 9.00 | 1.02 | 0.56 | 27.30 |
L6 | 2.55 | 10.00 | 10.00 | 6.00 | 2.5 | 0.33 | 0.80 | 6.00 | 0.64 | 0.99 | 39.81 |
* L1-L6 = Location 1-6.
* Iron (Fe). cadmium (Cd), mercury (Hg), arsenic (As), nickel (Ni), selenium (Se), chromium (Cr), lead (Pb), zinc (Zn), and copper (Cu).
Chronic daily intake (CDI; mg/kg/day) of heavy metals in swimming pools via oral and dermal routes
CDI BY ORAL EXPOSURE |
||||||||||
---|---|---|---|---|---|---|---|---|---|---|
Swimming pool | Fe (×10-3) | Cd (×10-5) | Hg (×10-5) | As (×10-4) | Ni (×10-4) | Se (×10-5) | Cr (×10-5) | Pb (×10-5) | Zn (×10-3) | Cu (×10-4) |
L1 | 6.21 | 4.85 | 3.22 | 1.28 | 2.04 | - | 8.05 | 8.05 | 1.01 | 7.46 |
L2 | 6.74 | - | 4.85 | - | 1.45 | - | 11.27 | 14.49 | 6.23 | 8.05 |
L3 | 2.86 | 3.22 | - | 0.49 | 1.12 | 3.22 | 6.44 | 12.88 | 5.01 | 3.38 |
L4 | 5.55 | 1.61 | 1.61 | 0.81 | 0.48 | 1.61 | - | 8.05 | 3.06 | 29.30 |
L5 | 1.49 | 3.22 | - | - | 0.97 | 4.83 | 11.27 | 14.49 | 7.13 | 11.91 |
L6 | 0.80 | 4.85 | 1.61 | 0.97 | 0.81 | 1.61 | 6.44 | 9.66 | 4.43 | 21.25 |
L1 | 8.91 | 0.69 | 4.62 | 1.84 | 6.01 | - | 2.31 | 1.15 | 0.86 | 7.62 |
L2 | 11.34 | - | 6.93 | - | 4.15 | - | 3.23 | 2.07 | 5.34 | 11.55 |
L3 | 4.11 | 0.46 | - | 0.69 | 3.23 | 4.62 | 1.85 | 1.84 | 4.29 | 4.85 |
L4 | 7.96 | 0.23 | 2.31 | 1.12 | 1.39 | 2.31 | - | 1.15 | 2.62 | 42.04 |
L5 | 2.15 | 0.46 | - | - | 2.77 | 6.93 | 3.23 | 2.07 | 6.11 | 17.09 |
L6 | 1.17 | 0.69 | 2.31 | 1.39 | 2.31 | 2.31 | 1.85 | 1.38 | 3.79 | 30.49 |
RfD** | 0.7 | 1×10-3 | 4×10-5 | 3×10-4 | 2×10-2 | 5×10-3 | 3×10-3 | 3.5×10-3 | 3×10-1 | 1×10-2 |
* L1-L6 = Location 1-6.
* Iron (Fe). cadmium (Cd), mercury (Hg), arsenic (As), nickel (Ni), selenium (Se), chromium (Cr), lead (Pb), zinc (Zn), and copper (Cu).
** RfD: Reference dose.
Hazard quotient (HQ) of heavy metals and Total Hazard Index of swimming pools via oral and dermal exposure routes
Swimming pool | L1 | L2 | L3 | L4 | L5 | L6 | |
---|---|---|---|---|---|---|---|
Fe | ing (×10-3) | 8.87 | 9.62 | 4.08 | 7.92 | 2.12 | 1.14 |
Derm (×10-5) | 12.72 | 16.20 | 5.87 | 11.37 | 3.07 | 1.67 | |
Cd | ing (×10-2) | 4.85 | - | 3.22 | 1.61 | 3.22 | 4.85 |
Derm (×10-3) | 0.69 | - | 0.46 | 0.23 | 0.46 | 0.69 | |
Hg | ing | 0.81 | 1.21 | - | 0.40 | - | 0.40 |
Derm | 1.15 | 1.73 | - | 0.58 | - | 0.58 | |
As | ing | 0.43 | - | 0.16 | 0.27 | - | 0.32 |
Derm (×10-2) | 0.61 | - | 0.23 | 0.37 | - | 0.46 | |
Ni | ing (×10-2) | 1.02 | 0.72 | 0.56 | 0.24 | 0.48 | 0.40 |
Derm (×10-5) | 3.00 | 2.07 | 1.61 | 0.69 | 1.38 | 1.15 | |
Se | ing (×10-2) | - | - | 0.64 | 0.32 | 0.96 | 0.32 |
Derm (×10-4) | - | - | 0.92 | 0.46 | 1.38 | 0.46 | |
Cr | ing (×10-2) | 2.68 | 3.75 | 2.14 | - | 3.75 | 2.14 |
Derm (×10-3) | 0.77 | 1.07 | 0.62 | - | 1.07 | 0.62 | |
Pb | ing (×10-2) | 2.30 | 4.83 | 4.23 | 2.30 | 4.83 | 0.39 |
Derm (×10-4) | 0.33 | 0.59 | 0.53 | 0.33 | 0.59 | 0.39 | |
Pb | ing (×10-2) | 0.33 | 2.07 | 1.67 | 1.02 | 2.37 | 1.47 |
Derm (×10-5) | 0.28 | 1.78 | 1.43 | 0.87 | 2.03 | 1.26 | |
Cu | ing (×10-2) | 7.46 | 8.05 | 3.38 | 29.30 | 11.91 | 21.25 |
Derm (×10-4) | 7.62 | 11.55 | 4.85 | 42.04 | 17.09 | 30.49 |
* L1-L6 = Location 1-6.
* Iron (Fe). cadmium (Cd), mercury (Hg), arsenic (As), nickel (Ni), selenium (Se), chromium (Cr), lead (Pb), zinc (Zn), and copper (Cu).