New International Guidelines Promote Swimming Pool Health and Safety

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New International Guidelines Promote Swimming Pool Health and Safety

http://www.waterandhealth.org/newsletter/pool_health.html

Introduction

The World Health Organization (WHO) has published new health and

safety guidelines for swimming pools and hot tubs, providing a

comprehensive, evidence-based resource to help facility operators and

public health officials maintain healthy conditions for swimming pool

users and employees. The May 2006 Guidelines for Safe Recreational

Water Environments, Volume 2: Swimming Pools and Similar Environments

(Guidelines) took over 10 years to develop, and involved the

participation of numerous institutions and more than 60 experts from

20 countries worldwide.

The Guidelines discuss the available knowledge of key health and

safety hazards associated with swimming pools, hot tubs and similar

facilities, and present a broad range of strategies covering design,

construction, operation and management to minimize these hazards.

This document also serves as a framework for policy makers and

regulators.

Where possible, WHO provides numerical guideline values as indicators

of safety or good management practices. These values were developed

using a risk-benefit approach, considering not only potential risks,

but also the significant benefits - including aerobic exercise -

related to use of these facilities. According to WHO, when a

guideline value is exceeded, this should prompt an investigation to

determine the cause of the failure and the likelihood of recurrence,

and to identify corrective actions needed to address the immediate

hazard and prevent similar conditions in the future.

This Water Quality and Health article summarizes several key elements

of the Guidelines related to air and water quality, particularly

those focused on preventing the spread of waterborne illnesses.

Primary Water and Air Quality Challenges

The Guidelines address three main water and air quality challenges,

ranked in order of public health importance:

1) Maintaining water clarity to minimize injury hazard

2) Protecting water quality to prevent the transmission of infectious

disease

3) Controlling potential hazards from chemical compounds

All of these challenges can be addressed through a combination of the

following:

Swimmer hygiene, including pre-swim showering, and preventing

accidental fecal releases into the pool;

Water treatment, including filtration (to remove particulates and

other contaminants) and disinfection (to remove/inactivate infectious

microorganisms and oxidize other contaminants during pool use);

Pool hydraulics to ensure effective distribution of disinfectant

throughout the pool, good mixing and removal of contaminated water;

Addition of fresh water at frequent intervals to dilute substances

that cannot be removed from the water by treatment);

Cleaning to remove biofilms from surfaces, sediments from the pool

floor and particulates adsorbed to filter materials; and

Adequate ventilation of indoor pools.

Proper Treatment and Other Good Management Practices Can Largely

Control Microbial Hazards

The Guidelines describe a variety of microorganisms that can be found

in swimming pools and related environments (see figure below). The

risk of illness associated with swimming pools is primarily linked to

fecal contamination of the water. However, a number of disease

causing microorganisms can be introduced through other routes.

For each type of microbial hazard, the Guidelines discuss known

disease outbreaks and provide information on risk assessment and risk

management. WHO reports that swimming pool-related outbreaks of

illness are relatively infrequent, and can largely be prevented

through proper disinfection, well-operated filters, swimmer hygiene,

and appropriate response to accidental fecal releases. Good

management practices are particularly important for chlorine-

resistant microorganisms such as Giardia and Cryptosporidium.

Adequate Disinfectant Levels Must Be Maintained Throughout the Pool

Many of the known outbreaks related to swimming pools have occurred

because disinfection was not applied or was inadequate. Disinfection

is part of the treatment process whereby disease causing

microorganisms are inactivated by chemical or physical means.

Chlorine-based disinfectants are the most widely-used, and include

chlorine gas, sodium hypochlorite, calcium hypochlorite and

chlorinated isocyanurates. Other processes use bromine-based

disinfectants, ozone, and ultraviolet (UV) radiation. The Guidelines

discuss the characteristics and uses of each, and considerations for

choosing a disinfectant and application system. A combination of

technologies may be used to take advantage of the strengths of

various technologies. For example, ozone and UV are each effective

against Cryptosporidium, but do not provide a residual disinfectant

in the pool and, therefore, must be used in conjunction with a

chlorine- or bromine-based disinfectant.

The Guidelines note that chlorination practices vary widely around

the world, as do recommended free chlorine levels. The Guidelines

state that adequate disinfection should be achieved with a free

chlorine level of 1 mg/l throughout the pool. They further recommend

that levels not exceed 3 mg/l in pools and 5 mg/l in hot tubs. The

range of 1- 3 mg/l for pools is somewhat lower than the range of 2-4

mg/l recommended by the Association of Pool and Spa Professionals in

the U.S. [and endorsed by the Water Quality & Health Council].

However, WHO recommends that acceptable levels of free chlorine

continue to be set at the local level, and that these levels must

always be consistent with satisfactory microbial quality. WHO also

notes that chlorine levels well above the recommended range may not

be of health significance, and that the primary issue would be

acceptability to swimmers.

The Guidelines also discuss " shock dosing " with chlorine as part of a

strategy of proper pool management. Shock dosing is used to control a

variety of pathogens and nuisance microorganisms and to destroy

organic contaminants and chloramine compounds (discussed more fully

below). As a preventive measure, routine shock dosing typically

involves raising free chlorine levels to at least 10 mg/l for between

1 and 4 hours. Addressing a specific water quality problem (such as

an accidental fecal release) may involve raising the free chlorine

residual to 20 mg/l for an 8 hour period while the pool is

unoccupied.

Disinfectants and DBPs Pose Little Risk in Well Managed Pools

The Guidelines assess hazards from disinfection byproducts (DBPs),

compounds formed by the reaction of disinfectants with various

organic compounds. Most information available relates to the

reactions of chlorine, while less is known about byproducts of other

disinfectants.

WHO's Guidelines for Drinking-water Quality can be used as a

screening tool for potential risks associated with DBPs in swimming

pools, while making appropriate allowance for the much lower

quantities of water ingested, shorter exposure periods and

proportionally higher non-ingestion exposure for pools. According to

WHO, DBP concentrations below the drinking water guideline values can

be achieved consistently in well managed pools. WHO also notes that

since the drinking water guideline values reflect tolerable risks

over a lifetime, this provides an additional level of reassurance.

Overall, WHO concludes, " The risks from exposure to chlorination

byproducts in reasonably well managed swimming pools would be

considered small and must be set against benefits of aerobic exercise

and risks in the absence of disinfection. "

Strategies to Control Irritating Chloramines in Water and Air

The Guidelines give particular attention to chloramines and

bromamines, which are formed when chlorine and bromine disinfectants

react with ammonia and nitrogen containing substances in the water.

Two of these compounds, nitrogen trichloride and nitrogen tribromide,

are volatile and can give rise to significant eye and respiratory

irritation in swimmers and pool attendants. Nitrogen trichloride has

a strong and unpleasant odor [often mistakenly attributed to an

excess of chlorine]. The Guidelines discuss studies that suggest a

number of health symptoms associated with exposure to the atmosphere

of indoor swimming pools, including respiratory symptoms likely to be

particularly pronounced in those suffering from asthma. Various

authors have suggested these were associated with nitrogen

trichloride in particular, but the studies were not able to confirm

this.

WHO recommends a provisional guideline value of 0.5 mg/m3 for

nitrogen trichloride in the atmosphere of indoor pools and hot tubs,

noting that additional data are needed to draw firm conclusions on

health risks.

The Guidelines emphasize the need to optimize the management of

indoor pools to reduce chloramines exposure, particularly for

competitive swimmers and other heavy users of pools. Elements of a

management strategy may include:

Minimizing the introduction of precursors through bather hygiene

(e.g., pre swim showering); Removing precursors through filtration

and other treatment; Periodic shock dosing of pool water - raising

free chlorine levels to at least 10 times the level of chloramines;

and Ventilating the air with at least 10 liters of fresh air/s/m2 of

water surface area.

All Stakeholders Have a Role in Guideline Implementation

To address the hazards discussed earlier, it is necessary to

implement effective strategies at multiple levels. The final chapter

of the Guidelines outlines responsibilities for various stakeholders,

including those in charge of:

design and construction of facilities, which will impact the ability

to ensure safe operations once the pool is in use;

operation and management, including the preparation of and compliance

with a comprehensive pool safety plan;

providing public education and targeted information to pool users;

and

regulatory requirements and enforcement at the national and/or local

level.

The Guidelines provide a series of examples of good practices in each

area. WHO emphasizes that successful implementation of these

practices will require suitable capacities and expertise, as well as

a coherent policy and legislative framework to assign

responsibilities and ensure accountability.

Water Quality & Health articles are published periodically by the

Water Quality & Health Council, an independent, multidisciplinary

group that promotes science based practices and policies to enhance

water quality and health by advising industry, health professionals,

policy makers and the public.