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A Comparison Between Freshwater and

Seawater Swimming Pools:

From Chemical Profile to Genotoxicity

Tarek Manasfia, Michel De Meob, Bruno Coulomba, Carole Di Giorgiob,

Jean-Luc Boudenne a

a Environmental Chemistry Laboratory b Environmental Mutagenesis Laboratory

Aix-Marseille University, France

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Why interested in seawater pools

• Among studies about swimming

pools, only few have looked at the

occurrence of DBPs in seawater

pools

• In seawater pools, brominated

DBPs are expected to be formed,

known to be more toxic than

chlorinated ones

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Thalassotherapy, at a Glance

• Seawater pools can be found in thalassotherapy centers,

an emerging and rapidly growing sector

• Formerly limited to patients, nowadays attendees are not

only curists but also mere tourism and wellness seekers

• Attendees expect wellbeing and beneficial health effects

so the question of chemical safety remains a concern

(Schwartz, 2005; Johnston et al., 2011)

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• Mainly indoor

• Natural seawater

• pH = 8 – 8.5

• Disinfection: HOCl…

HOCl/OCl- + Br

- HOBr/OBr

- + Cl

-

• Brominated DBPs, more toxic

• Temperature: 30 - 35 ᵒC

Seawater Pools (thalasso)

• Indoor or outdoor

• Tap/freshwater

• pH = 7

• Disinfection: HOCl…

• Chlorinated DBPs

• Temperature: 25 - 30 ᵒC

Pools Characteristics: Seawater Vs. Freshwater

Freshwater Pools

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Objectives of Study

Determine DBP contents in seawater swimming

pools and compare them to a reference freshwater

pool

Assess the genotoxic properties of pool water

concentrates/extracts

Relate genotoxicity results to the DBP chemical

composition

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Study Site

Four swimming pools in two establishments

(E1 and E2) located in Southeast France

Establishment E1 Establishment E2

Indoor seawater

Outdoor freshwater

Two indoor

Seawater pools

Pre-filtration on sand

Disinfection with Bleach

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Methodology

Sampling

On-site

measurements

Laboratory

measurements

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Methodology

Sampling

On-site

measurements

Laboratory

measurements

Temperature,

pH, turbidity,

salinity

Free

chlorine,

total chlorine

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Methodology

Sampling

On-site measurements Laboratory measurements

Temperature,

pH, turbidity,

salinity

Genotoxicity

assessment

(Ames test)

TOC and

DBPs (THM,

HAA, HAN,

HK, THA)

Samples conserved at

4°C till treatment

Free

chlorine,

total chlorine

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Treatment of Samples in Laboratory

DBP Analysis

Acidification

and LLE (MTBE)

With or without derivatization

Addition of IS

Injection GC-ECD

Genotoxicity Assay

Sample Analysis in triplicates

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Treatment of Samples in Laboratory

DBPs Analysis

Acidification

and LLE (MTBE)

With or without derivatization

Addition of IS

Injection GC-ECD

Genotoxicity Assay

Resin Extraction:

XAD-8/XAD-2 in a column

Eluant ethyl acetate

Solvent Exchange (DMSO)

Concentrate x 20,000

Ames test

± S9 fraction

Sample Analysis in triplicates

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Results

Freshwater

Pool E1

Seawater

Pool E1

Seawater

Pool E2 (1)

Seawater

Pool E2 (2)

T (°C) 29.4 33.2 30.9 33.4

pH 7 8.54 8.46 8.32

Salinity (PSU) 1.15 51.87 44.55 44.32

TOC (mg C/L) 11.52 11.88 10.88 11.82

Free Chlorine (mg/L) 1.55 1.39 1.16 1.05

Global Parameters

TOC levels were of the same order in all the pools

However, freshwater pool was remarkably more frequented

Freshwater pool was outdoors higher volatilization

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Analysis of DBPs

• THM

• HAA

• HAN

• HK

• THA

Results

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Results: Analysis of DBPs

Trihalomethanes (THMs)

Major THM: Chloroform in freshwater pool Vs.

Bromoform in seawater pools

TH

M c

once

ntr

atio

n (

µg/L

)

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Results: Analysis of DBPs

Haloacetic acids (HAAs)

HAA-9

=

501.2 µg/L

HAA-9

=

109.0 µg/L

HAA-9

=

134.3 µg/L

HAA-9

=

108.1 µg/L

Major HAA: Trichloroacetic acid in Freshwater Vs.

Dibromoacetic acid in seawater

92%

5%

54%

40%

58%

36% 33%

59%

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Results: Analysis of DBPs

Haloacetonitriles (HANs) H

AN

con

cen

tration

(µ

g/L

)

Major HAN: DCAN in freshwater pool Vs. DBAN in

seawater pool

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Results: Analysis of DBPs

Trihaloacetaldehydes (THA) T

HA

Co

nce

ntr

atio

n (

µg/L

) (

log s

ca

le)

Levels of chloral hydrate in the freshwater pool are far

higher than the levels of bromal hydrate in seawater pools

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Results: Analysis of DBPs

DBPs: Freshwater Vs. Seawater Pools

Main DBP classes:

HAAs the most abundant in all pools followed by

trihaloacetaldehydes in freshwater pool and THMs

in seawater pools

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Results: Analysis of DBPs

DBPs: Freshwater Vs. Seawater Pools

DB

Ps c

on

cen

tration

(µ

g/L

)

Higher DBP content in freshwater pool than in seawater pools

Frequentation rates difference seems responsible

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Origin of found DBPs

Are the found DBPs from natural organic matter or

anthropogenic origins?

1- Levels of HAAs and HANs suggest the implication of

anthropogenic organic matter!

2- Pre-filtration of water is supposed to eliminate to a large

extent the NOM present in source water

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Results: Genotoxicity (Ames Test)

Freshwater samples Seawater samples

Without S9 mix: 3.7 rev/mL-eq 0.4 rev/mL-eq

With S9 mix: 1.8 rev/mL-eq 0.3 rev/mL-eq

Mutagenic Potencies

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Results: Genotoxicity (Ames Test)

Dose-Response Relationships (without S9 mix)

Water samples from the freshwater pool E1 were

significantly more mutagenic than those from

seawater pool E1

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Conclusion: DBPs

Most DBPs in the freshwater pool were chlorinated Vs.

mostly brominated DBPs in the seawater pools

Levels of bromal hydrate in thalassotherapy seawater

pools were reported for the first time

Trihaloacetaldehyde levels discrepancy between

freshwater and seawater pools (instability at high pH)

In the seawater pools (pH ~ 8.3): total HAN < THM-4

In the freshwater pool (pH ~ 7.0): total HAN ≥THM-4

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Conclusion: Genotoxicity

Freshwater samples were more mutagenic than

seawater samples, this seems to be related to the high

DBP content

Although brominated DBPs are known to be more

genotoxic than chlorinated DBPs, the overall mixture

effect seems more important than individual effects

High frequentation rates seems responsible for high

content in DBPs, which in turn seems responsible for the

mutagenic properties

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Perspectives

Further research into the chemistry of swimming pool

waters to determine the unknown DBPs

Identification of the DBP fractions and classes

contributing mainly to the observed mutagenicity and

their routes of exposure

Examination of other potential health effects of DBPs

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Perspectives

Identification of the anthropogenic loads (body fluids,

PCPs…) that largely contribute to the formation of DBPs

Efforts to reduce DBPs: educating the public about

importance of hygiene measures, (stricter) regulations…

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Thank you!