Chemicals in the water and air at public swimming pools

Ref: HPHS-8FEBEY

Dear Mr McDermott,

Thank you for your enquiry regarding swimming pools.

Infoline is unable to respond to your enquiry as it requires a specialist
response. Therefore it has been forwarded for reply to:

Adrian Tinson
Services, Transportation & Safety Unit
Health and Safety Executive
1st Floor
Mercantile Chambers
53 Bothwell Street
Glasgow
G2 6TS
Telephone: 0845 345 0055

If you require to contact HSE again regarding this enquiry please quote the
above reference number.

I hope this helps, but if you require further assistance, please do not
hesitate to contact this address again or telephone HSE Infoline on 08453
450055.

Yours sincerely

Helena Phillips

HSE Infoline

HSE is committed to maintaining your personal information in a manner that
meets the requirements of the Data Protection Act 1998.
Sometimes, we may need to pass your details to another government
department or public body so that they can help you with your enquiry.

HSE Infoline is provided by Connaught Compliance Services Ltd on behalf of
HSE

Thank you for your enquiry about chemicals in the water and air at public
swimming pools.

As this is not a request for information held by HSE, it will not
be treating as a Freedom Of Information Request. Instead, as it is an
enquiry asking for HSE's view on chemicals in the water and air at public
pools, I will reply on that basis in due course.

Regards

Adrian Tinson
HMI health & safety, HSE Entertainment & Leisure sector

show quoted sections

Communications via the GSi may be automatically logged, monitored and/or
recorded for legal purposes.

Ref: HPHS-8FTBZQ

Dear Mr Mc Dermott,

Thank you for your enquiry regarding WELs for THMs and nitrogen
trichloride.

Neither THMs and nitrogen trichloride are listed in HSE's publication
regarding exposure limits.

However, the HSE do not assign WELs for all substances. If the substances
that are being used does not have a WEL assigned, then you must apply the
general COSHH assessment process to it's use.

The following information has been taken from the HSE's Approved Code of
Practice to the Control of Substances Hazardous to Health Regulations 2002:

Inhaled substances not assigned WELs

The absence of a substance from the lists of WELs does not mean that it is
safe. Many substances do not have a WEL. For these substances, employers
should apply the principles of good practice for the control of substances
hazardous to health to control exposure to a level to which nearly all the
working population could be exposed, day after day at work, without adverse
effects on health. HSE has published good practice advice to help employers
decide on suitable control measures. Available material includes the
guidance on Schedule 2A, COSHH essentials, process - specific guidance for
a number of common processes and Chemical Hazard Alert Notices (CHANs). A
list of CHANs and other HSE guidance currently available can be viewed on
the HSE website at www.hse.gov.uk/pubns. In addition, employers can obtain
information about the substance concerned from a number of other sources,
including:

(a) manufacturers and suppliers of the substance;

(b) industry associations; and

(c) occupational medicine and occupational hygiene journals.

If it is not possible to identify suitable exposure control measures using,
for instance, COSHH essentials and no WEL exists it may be possible and
useful to identify or develop an exposure standard. Suppliers, trade
associations or specialist advisers may be able to help.

Reference: L5, General COSHH ACOP, Carcinogens ACOP and Biological Agents
ACOP (Fifth edition), ISBN 9780717629813, £12.50

The regulations state the following with regards to assessing the risks
from the use of substances which are hazardous to health:

Regulation 6: Assessment of the risk to health created by work involving
substances hazardous to health
Regulation

(1) An employer shall not carry out any work which is liable to expose
any employees to any substance hazardous to health unless he has:

(a) made a suitable and sufficient assessment of the risk created by
that work to the health of those employees and of the steps that need to be
taken to meet the requirements of these Regulations; and

(b) implemented the steps referred to in sub-paragraph (a).

(2) The risk assessment shall include consideration of:

(a) the hazardous properties of the substance;

(b) information on health effects provided by the supplier, including
information contained in any relevant safety data sheet;

(c) the level, type and duration of exposure;

(d) the circumstances of the work, including the amount of the
substance involved;

(e) activities, such as maintenance, where there is the potential for a
high level of exposure;

(f) any relevant workplace exposure limit or similar occupational
exposure limit;

(g) the effect of preventive and control measures which have been or
will be taken in accordance with regulation 7;

(h) the results of relevant health surveillance;

(i) the results of monitoring of exposure in accordance with regulation
10;

(j) in circumstances where the work will involve exposure to more than
one substance hazardous to health, the risk presented by exposure to such
substances in combination;

(k) the approved classification of any biological agent; and

(l) such additional information as the employer may need in order to
complete the risk assessment.

(3) The risk assessment shall be reviewed regularly and forthwith if:

(a) there is reason to suspect that the risk assessment is no longer
valid;

(b) there has been a significant change in the work to which the risk
assessment relates; or

(c) the results of any monitoring carried out in accordance with
regulation 10 shows it to be necessary,

and where, as a result of the review, changes to the risk assessment are
required, those changes shall be made.

(4) Where the employer employs 5 or more employees, he shall record:

(a) the significant findings of the risk assessment as soon as is
practicable after the risk assessment is made; and

(b) the steps which he has taken to meet the requirements of regulation
7.

The COSHH risk assessment
Guidance
The purpose of the assessment is to enable the employer to make a valid
decision about the measures necessary to prevent or adequately control the
exposure of their employees to substances hazardous to health arising from
the work. It also enables the employer to demonstrate readily, both to
themselves and to others who may have an interest, eg safety
representatives, enforcement authorities etc that they have:

(a) considered all the factors pertinent to the work;

(b) reached an informed and valid judgement about the risks;

(c) considered the practicability of preventing exposure to hazardous
substances;

(d) considered the steps which need to be taken to achieve and maintain
adequate control of exposure where prevention is not reasonably practicable
in accordance with regulation 7;

(e) considered the need for monitoring exposure at the workplace as
part of validating an initial or conditional assessment and for health
surveillance; and

(f) identified other action necessary to comply with regulations 8-13.

The assessment may be initial or conditional, ie it may prescribe measures
that are likely to adequately control exposure, but which need to be tested
to confirm their effectiveness. Such measures may subsequently be found to
be unnecessary, for example personal protective equipment (PPE) may be
provided as a precautionary measures, which is later found not to be
required.
The COSHH assessment can be made as part of, or as an extension of, the
more general risk assessment duties placed on employers by regulation 3 of
the Management Regulations. If the substances hazardous to health present
in the workplace are also a risk to the safety of employees, eg they are
flammable, unstable etc, the employer may find it helpful to combine the
COSHH risk assessment with that required by regulation 5 of DSEAR.

Safety data sheets
In many circumstances employers will only need to read suppliers' safety
data sheets to decide whether their existing practices are sufficient to
ensure adequate control of exposure. In other circumstances, and in
particular for new activities, employers may need to consult HSE guidance
notes, manufacturers' standards, technical papers, trade literature etc to
estimate the likely exposure before deciding what control measures they
should apply.

ACOP
Employers making an assessment of an activity which exposes employees to a
substance (or preparation) which is classified as dangerous for supply
under CHIP, must consider and take into account the information the
supplier provides on the CHIP safety data sheet (the data sheet). These
provide users of dangerous substances with some of the information they
need to protect the health of employees and for handling the substance
safely in the workplace. The data sheet contains information under a number
of obligatory headings, eg 'Hazard identification', 'Exposure controls:
personal protection' and so can be a useful source of information in
helping employers make the decisions required for the assessment.

Guidance
Accurate, complete and correct information on data sheets is essential when
considering workplace controls, eg over-classification of a substance might
lead to unnecessarily stringent controls, while under-classification may
result in risks to employees' health. If employers have concerns about the
quality and reliability of information provided on a data sheet, or if they
are unsure of the application of the information to their situation, they
should contact the supplier for clarification or for further guidance.
The process of carrying out an assessment is not a bureaucratic exercise or
simply the collection of information resulting in mountains of paper to be
filed away and forgotten. Collecting manufacturers' or suppliers' data
sheets and other information does not in itself meet the COSHH requirements
to carry out an assessment. Gathering the information is only the first
stage in the assessment process. The information must then be used to
determine the appropriate control measures needed to protect the health of
employees.

Biological agents
For biological agents, as distinct from other substances hazardous to
health, the assessment should reflect the ability they may have to
replicate and infect. In general, there will not be a dose-response
relationship of the kind that exists for many other substances, and risk
may be high at small exposures. Relevant information on the nature of a
particular agent includes that prepared by the Advisory Committee on
Dangerous Pathogens.

The person who carries out the assessment
ACOP
Employers must ensure that whoever carries out the assessment and provides
advice on the prevention and control of exposure is competent to do so in
accordance with regulation 12(4). This does not necessarily mean that
particular qualifications are required. However, whoever carries out the
assessment should:

(a) have adequate knowledge, training and expertise in understanding
hazard and risk;

(b) know how the work activity uses or produces substances hazardous to
health;

(c) have the ability and the authority to collate all the necessary,
relevant information; and

(d) have the knowledge, skills and experience to make the right
decisions about the risks and the precautions that are needed.

The person who carries out the assessment does not always have to be fully
familiar with the requirements of COSHH and the ACOP. However, that person
should have access to someone who has a firm grasp of those requirements.
This pooling of knowledge would allow, for example, a supervisor's
experience of a process to be combined with the technical and legal
knowledge of a health and safety manager.
If more than one person contributes to the assessment, the employer should
ensure that each person knows precisely what they are to do, and nominate
one person to co-ordinate, compile and record the significant findings.

Making a suitable and sufficient assessment
The assessment should determine whether there are any substances hazardous
to health (including biological agents) at the workplace to which employees
are liable to be exposed, and in a form in which the substance can be
inhaled, ingested or absorbed through the skin.
Assessment of the risks created by any work must be comprehensive and cover
those items listed in regulation 6(2). It should take into account those
substances which are:

(a) brought into the workplace and handled, stored and used for
processing;

(b) produced or given off, eg as fumes, vapour dust etc by a process or
an activity or as a result of an accident or incident;

(c) used for, or arise from maintenance, cleaning, and repair work;

(d) produced at the end of any process, eg wastes, residues, scrap etc;
and

(e) produced from activities carried out by another employer's
employees in the vicinity.

For those hazardous substances brought into and used in the workplace, the
employer's first priority is to prevent exposure to the substance by
identifying and substituting a non-hazardous or less hazardous alternative.
This should be a thorough and comprehensive process:

(a) in which the employer considers and evaluates the hazards posed by
any alternative substances that are available and the degree of risk they
may present in the work activity concerned; and

(b) which results in the employer selecting for use the substance that
produces the least risk for the circumstances of the work.

Where a substance is a known or suspected carcinogen or mutagen, there is a
more compelling reason for the employer to make every effort to substitute
a non-carcinogenic or non-mutagenic alternative.
The assessment of the risks created by the work activity should also
include consideration of:

(a) the properties, ie physical, chemical or biological of the
substances and the effects they could have on the body;

(b) where those substances are likely to be present and in what form,
eg dust, vapour, mist, fume etc and whether they are used or produced, and
in what amounts and how often;

(c) the ways in which and the extent to which any groups of people
could be exposed, including maintenance workers who may work in
circumstances where exposure is foreseeably higher than normal: office
staff, night cleaners, security guards, members of the public such as
visitors, patients etc, taking into account the type of work and process,
and any reasonably foreseeable deterioration in, or failure of, any control
measure provided;

(d) the need to protect particular groups of employees who may be at an
increased risk, eg inexperienced trainees and young people aged under 18;
pregnant workers; disabled workers; and any employees known to be
susceptible to certain illnesses such as dermatitis, asthma or other
diseases which may be caused by exposure to hazardous substances;

(e) an estimate of exposure, taking into account any information that
may be available about:

(i) the concentration likely to be produced by the work concerned;

(ii) the effort needed to do the work and how this may affect the
rate and volume of air employees breathe (for some work activities,
employees might breathe three or four times the volume of air that
they would breathe at rest); and

(iii) the effect of any engineering measures and systems of work
currently used for controlling potential exposure. To complete the
assessment, it may be necessary to carry out atmospheric sampling and
measurement to determine exposure, particularly where operations are
complex or specialised and the substances involved have an
occupational exposure limit;

(f) how the estimate of exposure compares with any existing, valid
standards which represent adequate control, eg an occupational exposure
limit or 'biological monitoring guidance value'.

Employers should give particular consideration to activities which can give
rise to the highest exposures, eg cleaning of equipment, work in confined
spaces, or non-routine or end-of-shift tasks. Understanding the factors
that contribute to employees' exposure will help employers decide how to
control it.
If a comparison of the estimate of exposure with any existing valid
standards, which represent adequate control, shows that control is likely
to be inadequate then the assessment should also describe the extra steps
needed to obtain and maintain adequate control, eg better enclosure and
extraction.

Exposure to two or more substances
Where a work activity may expose employees to more than one substance
hazardous to health, the employer must consider the possible enhanced
harmful effects of combined or sequential exposures. If employees are under
health surveillance which is being supervised by a doctor or other health
professional, the employer should seek advice from the medical person
concerned. Otherwise, information may be available from other sources such
as the individual suppliers of the substances, trade associations or
guidance material etc.

Assessment of the risks from biological agents
For exposure to biological agents, the employer should consider in
particular:

(a) the hazard groups of any biological agents that may be present and
what form they may be in, eg infectious stages or hardy spores;

(b) how and where they are present, how they are transmitted and the
diseases they cause; and

(c) the likelihood of exposure and consequent disease (including the
identification of workers and non-workers, eg hospital patients, who may be
particularly susceptible, for example because they are immunocompromised),
drawing on evidence of the prevalence of infection or other ill effect as
experienced within a particular industry sector or workplace.

In certain circumstances, for example in medical facilities or livestock
farming, the assessment should take account of uncertainties about the
presence of infectious agents in patients or animals. The risks associated
with tissues and other waste material removed from patients and animals, or
specimens sent for examination, should be assessed at each stage of
handling, for example during clinical care, surgery, biopsy and other
specimen collection, specimen handling and transportation, laboratory
examination and waste disposal.

Using personal protective equipment to secure adequate control of exposure
In deciding what measures are needed to control exposure, employers should
only use personal protective equipment (PPE) so far as is reasonably
practicable after all other measures have been taken. Employers may use PPE
as secondary protection in combination with other control methods such as
local exhaust ventilation, if those other control measures do not
adequately control exposure by themselves. However, there may be
circumstances where an employer considers it prudent to issue personal
protective equipment such as clothing, face shields, gloves etc, not
because other control measures are inadequate on their own, but to provide
employees with additional protection should any of those measures fail.

Recording the significant findings
All employers must carry out an assessment but those employing five or more
employees must also record the significant findings. Although employers
with fewer than five employees are exempt from this recording requirement,
they are strongly advised to record the significant findings of their
assessments as a matter of good practice. Employers can use the recorded
findings as evidence:

(a) to show the enforcing authorities that they have carried out a
suitable and sufficient assessment in accordance with regulation 6(1); and

(b) to demonstrate that they have systematically considered all the
factors relevant to the work, and put in place measures either to prevent
exposure or to achieve and maintain adequate control of exposure.

The significant findings of the risk assessment should represent an
effective statement of hazards, risks and actions taken to protect the
health of employees and anyone else who may be affected by the work.
Employers will need to record sufficient detail of the assessment itself so
that they can demonstrate to a safety representative or inspector etc that
they have carried out a suitable and sufficient assessment. The record may
refer to and rely on other documents and records describing procedures and
safeguards.
The record may be in writing or recorded by other means, eg electronically
so long as it is readily accessible and retrievable at any reasonable time
for use by employers in reviews or for examination, eg by a safety
representative or inspector etc.
The amount of information employers should record will be proportionate to
the risks posed by the work. In the simplest and most obvious cases where a
work activity involving exposure to a hazardous substance poses little or
no risk, eg for many of the substances often found in small quantities in
offices or homes, the employer need only record:

(a) the substances to which the employees are or are likely to be
exposed and the form in which they occur: liquid, powder, pellets, dust
etc;

(b) the measures taken under regulation 7 to adequately control
exposure, eg taking account of the information provided by the supplier,
and using the substances in accordance with their accompanying
instructions; and

(c) a statement that because the substances pose little or no risk, no
further detailed risk assessment is necessary.

Where exposure to a number of different hazardous substances pose little or
no risk to the health of employees, the employer may group together on a
single record the significant findings of the assessments for all the
individual substances concerned. The record may also group together the
significant findings for similar substances of low risk, eg lubricants or
detergents.
However, where the work concerned presents more of a risk to health, the
significant findings of the assessment should comprise a more comprehensive
record. It should include at least the appropriate items from the following
list:

(a) the processes or activities in which the substances are used or
produced and how employees may be exposed to them;

(b) the substance(s) to which the employees are liable to be exposed
and the form in which it/they occur, eg liquid, gas, vapour, powder;

(c) the hazards and risks the substances present under normal
conditions of use, and in circumstances of an unforeseen incident, accident
or emergency which could result in an uncontrolled release of the substance
concerned into the workplace;

(d) the extent to which prevention and substitution of a substance or
process was considered (see regulations 7(1)(2));

(e) identification of the employees or groups of employees liable to be
exposed;

(f) the preventive measures in place to achieve adequate control of
exposure, including the use of any personal and respiratory protective
equipment (RPE). (These need not duplicate details of measures more fully
described in other documents such as standard operating procedures but
could refer to them);

(g) the commissioning, monitoring and testing required as part of the
process of validating the effectiveness of and refining control measures;

(h) whether it is necessary to carry out atmospheric sampling and
measurement and the frequency with which any further air monitoring will be
carried out;

(i) where appropriate, the reasons for selecting particular types of
PPE, including where appropriate RPE, to secure adequate control of
exposure;

(j) the conclusions reached on the risks to the health of employees and
to any other people who may be affected by the work concerned, taking
account of the control measures being used;

(k) whether it is appropriate to place any identified groups of
employees under health surveillance (regulation 11);

(l) when the assessment will be reviewed or the period between
successive reviews.

This record of the significant findings will also form the basis for a
revision of the assessment.
The employer should record the significant findings when the assessment is
made or as soon as is practicable afterwards. In some circumstances, not
all the significant findings will have been determined at the same time:
some may be awaiting further information before they can be resolved and it
will not be possible to record these until then, eg air monitoring results.
In these situations, the employer should complete or update the significant
findings as soon as the information becomes available. However, the
employer must ensure that while waiting for information to confirm the
conclusions drawn from the assessment, a cautious approach is adopted to
ensure that employees' exposure to substances hazardous to health is
adequately controlled, eg in emergency situations where operational
decisions have to be made and remedial action taken immediately, or in
circumstances where there is a pilot operation which must be run for a
period before being assessed completely.

Reviewing the assessment
The record of the assessment should be a living document, which must be
revisited to ensure that it is kept up to date. The employer should make
arrangements to ensure that the assessment is reviewed regularly. The date
of the first review and the length of time between successive reviews will
depend on the type of risk, the work and the employer's judgement on the
likelihood of changes occurring.
The assessment should be reviewed immediately:

(a) when there is evidence to think that it may no longer be valid, for
example from:

(i) the results of examinations and tests of engineering controls
(regulation 9);

(ii) the results of monitoring exposure (regulation 10);

(iii) the results of health surveillance, eg the identification of
an adverse health effect or a confirmed case of work-related disease
(regulation 11(9)); or new information on health risks; or

(iv) reports or complaints from supervisors, safety
representatives or employees about defects in the control systems;

(b) where there is to be or has been a significant change in the
circumstances of work, especially one which may have affected employees'
exposure to a substance hazardous to health. For example:

(i) a change in the substances used, including the introduction of
a substitute substance, or their source;

(ii) in plant modification, including engineering controls;

(iii) a process or method of work which is likely to affect the
nature of the hazard, eg changes in the exhaust ventilation system;

(iv) in the volume or rate of production; or

(v) a reduction in the workforce without any corresponding
reduction in the rate of production and the consequential additional
pressures on employees.

Where the assessment is changed and control measures changed or adapted to
meet the new circumstances, employers must take action to implement any
necessary changes identified by the review and record afresh the
significant findings.
When reviewing the assessment, employers should use the opportunity to look
again at their prevention or control measures. In particular, they should:

(a) reconsider whether it is practicable to prevent exposure to
hazardous substances by changing the process or by using a non-hazardous
substance. This may be possible because of technological developments, or
changes in the relationship between costs and substances, equipment used
and control measures;

(b) reconsider whether it is practicable to use a less hazardous form
of the same substance;

(c) re-examine existing control measures to decide whether they can be
improved.

Consulting employees and their representatives
Employers should involve their employees, and/or their safety
representatives where they are appointed, in the processes of carrying out
and reviewing risk assessments. They are in a good position to know what
happens in practice and they will use the controls that the employer
introduces. Employers can involve their employees as part of their duties
under regulation 12 of COSHH to provide them with suitable information,
instruction and training. Employers should also:

(a) tell employees or their workplace representatives the results of
the assessment;

(b) explain how control measures are designed to protect their health
from substances hazardous to health; and

(c) explain how any changes will affect the way the employees do the
work in the future.

Help with the risk assessment

COSHH essentials
Guidance
The HSC's Advisory Committee on Toxic Substances has developed COSHH
essentials as a generic risk assessment scheme for a wide range of
hazardous substances covered by CHIP and COSHH. It leads users to
appropriate control advice for a range of common tasks, eg mixing,
weighing, spray painting. COSHH essentials is available both in printed and
electronic (web-based) formats, and can be used as a basis for the
recording of the risk assessment. While COSHH essentials has been designed
to ensure that a precautionary approach is taken towards control, it is a
generic guide and cannot guarantee that in all circumstances it will lead
to full compliance with the Regulations' assessment and control
requirements. At present, COSHH essentials addresses risks from some of the
more hazardous substances, eg some substances that cause asthma or cancer
(and it will cover more of these in the future). For those substances not
covered, COSHH essentials recommends users seek specialist advice. Details
are contained in the publication COSHH essentials: Easy steps to control
chemicals. The electronic COSHH essentials can be found at
www.coshh-essentials.org.uk.

Other sources of help
HSE's publication A step by step guide to COSHH assessment provides more
general guidance on the stages in carrying out COSHH risk assessments.

Some industries, trade associations, industry advisory councils, health
departments and professional bodies etc produce guidance publications
setting out COSHH-related best practice for the industry concerned.
Employers may find these other publications helpful in carrying out their
assessments.

Employers who decide to use the services of a consultancy to carry out
their assessment(s), or to design and check the effectiveness of control
measures should ensure that they are competent to do the work. One way to
do this is to use one listed in the British Institute of Occupational
Hygienists (BIOH) Directory of Consultancies. Contact BIOH at Suite 2,
Georgian House, Great Northern Road, Derby DE1 1LT Tel: 01332 298087
Website: www.bioh.org.uk.

Reference: L5, General COSHH ACOP, Carcinogens ACOP and Biological Agents
ACOP (Fifth edition), ISBN 9780717629813, £12.50
This can be accessed online at the following web address:

http://www.hse.gov.uk/pubns/priced/l5.pdf

Copies are also available from HSE Books:

HSE Books
PO Box 1999,
Sudbury,
Suffolk, CO10 2WA.
Tel: 01787 881165
Fax: 01787 313995
Email: [email address]
http://books.hse.gov.uk/hse/public/home....

Many of the free publications can also be downloaded from the HSE Website:
www.hse.gov.uk

There are three methods of payment currently available from HSE Books:
1. Via the post, bank cheques/ postal orders made payable to HSE Books
2. Via the telephone, American Express, Master Card, Visa or a debit card
3. Existing approved credit account customers may use the Banks Automated
Clearing System
(BACS). However, new accounts are not being set up.

I hope this helps, but if you require further assistance, please do not
hesitate to contact this address again or telephone HSE Infoline on
08453 450055.

Yours sincerely

Helena Phillips

HSE Infoline

HSE is committed to maintaining your personal information in a
manner that meets the requirements of the Data Protection Act 1998.
Sometimes, we may need to pass your details to another government
department or public body so that they can help you with your
enquiry.

HSE Infoline is provided by Connaught Compliance Services Ltd on
behalf of HSE

Dear Mr McDermott

Further to my intial reply dated 8th April 2011, I hope the following
information helps:

Failure to ensure that the water chemistry is balanced can result in high
microbial concentrations, or the production of Disinfection By Products
(DBPs) at concentrations that may cause adverse health effects.

A multitude of DBPs may be detected in swimming pool water and, depending
upon their volatility, within the air space above the water as a result of
chlorination. Two commonly found groups include chloramines (inorganic and
organic) and trihalomethanes (THMs) in addition to others such as cyanogen
chloride (more than 500 DBPs have been detected in chlorinated drinking
water). Inorganic chloramines are formed by chlorine reacting with
ammonia (a break down product of urea contained in urine) and other
proteins contained in human skin, sweat etc. Chloramines are monitored by
measuring the combined chlorine concentration in the pool water.

The three inorganic chloramines commonly encountered when water chemistry
is not balanced, include monochloramine (NH[2]Cl[)], dichloramine
(NHCl[2)] and trichloramine (NCl[3]), the latter also known as nitrogen
trichloride. It is the inorganic chloramines that produce the "swimming
pool" odours, not "free" chlorine that many imagine.

THMs (also known as haloforms e.g. chloroform is the commonest THM in
fresh water pools) are found in all chlorinated water systems including
the public water supply and swimming pool water. THMs in swimming pools
are formed by the reaction of chlorine with the organic
substances/materials generated by bathers. The largest source of human
exposure to THMs is from the consumption of drinking water. In addition to
inhalation, a significant route of exposure to chloroform is via the skin
from bathing or showering in the home. One study has suggested that a
greater concentration of chloroform passed through the skin when bathing
waters are heated.

UK legislation and limits

There are no Regulations specific to swimming pools in the UK. However,
general Health and Safety Legislation such as the Health and Safety at
Work etc Act 1974; the Management of Health and Safety at Work Regulations
(MHSWR) 1992 and in particular, regarding exposure to chemicals, the
Control of Substances Hazardous to Health (COSHH) Regulations 2002 (as
amended) apply both to staff and bathers in swimming pools. These
Regulations (and others) are detailed in HSE Guidance HSG 179 "Managing
Health and Safety in swimming pools).

Swimming pool water quality standards are contained in Guidance published
by the Pool Water Treatment Advisory Group (PWTAG). The Guidance contained
in "Swimming Pool Water - treatment and quality standards for pools and
spas" published by PWTAG is considered the standard that is normally
expected to be complied with in an efficiently managed swimming pool by UK
enforcing authorities (Health and Safety Executive and Local Authorities).

The above PWTAG Guidance recommends various guideline values to ensure
that the water chemistry is suitably balanced to provide adequate
disinfection whilst, in the case of chlorination, minimising the
production of unwanted combined chlorine concentrations (e.g.
chloramines). Ideally combined chlorine concentrations should be less than
1 mg/litre (1000 parts per billion - ppb) and less than half the free
chlorine value (normally 1 mg/litre for inorganic chlorine systems). By
controlling pool chemistry within these guidelines Nitrogen Trichloride
shouldn't be a problem should it become airborne because it's a strong
respiratory irritant at levels where combined chlorines are high (and
gives the pool odour).

The PWTAG Guidance makes reference to the World Health Organisation (WHO)
drinking water standards and standards contained in the Drinking Water
Directive (DWD) for the 4 commonest THMs found in chlorinated drinking
water (trichloromethane (chloroform), dibromochloromethane,
dichlorobromomethane and tribromomethane). The DWD standard for the 4 THMs
combined is 100 ug/litre (100 ppb) as a maximum value. PWTAG Guidance also
refers to a standard for competitive swimming, as recommended by FINA (the
International body for various swimming events), of 20 ug/litre (20 ppb)
maximum.

In the occupational environment (air), chloroform has been allocated a
Workplace Exposure Limit of 2 ppm (9000 ug/metre^3) 8-hour TWA (HSE
Guidance EH40/2005 "Workplace exposure limits refers) although this
value does not apply to members of the public.

European DIN norm and French Standards

Assessment methods and assessment of the actual risks of chemicals
themselves differ between countries. As a result, it is sometimes
difficult to compare exposure limits between countries because of these
differing approaches. That said, there is nothing to stop a UK pool
operator adopting the DIN norm and French standards if they meet or better
the limits/standards indicated above. However, at this present time, they
won't be assessed against either in the UK.

Summary

The production of DPBs in chlorinated water systems such as swimming pools
is well established. Because of the requirement to ensure (i) adequate
disinfection (and to avoid corrosion problems if free chlorine levels are
too high) and (ii) prevent acute health symptoms, it is established
practice to regularly monitor free chlorine and combined chlorine
levels (which includes Nitrogen Trichloride) in swimming pool water. It is
not normal practice to monitor THMs as a measure of water quality
(considered costly and difficult - reference PWTAG Guidance), although it
is recognised that THMs are produced in the swimming pool environment and
are unwanted by products of chlorination. Unfortunately, unlike
chloramines, there is no evidence that THMs will produce the health
effects at the concentrations reportedly found in swimming pools.

Various concentrations of volatile DBPs are always liable to be produced
when chlorinating disinfectants are used. Therefore in addition to
ensuring that the pool water chemistry complies with PWTAG guidelines,
indoor swimming pools require sufficient mechanical ventilation and air
mixing to maintain a comfortable indoor environment.

The system should be capable of removing the majority of volatile DBPs
from the air and controlling humidity (whilst ensuring a draught free
environment for bathers). A balanced general mechanical ventilation system
providing low level extraction at the sides of the pool and high level
supply air should normally provide between 4 - 10 air changes per hour to
achieve the desired results in a well managed pool.

Finally, in order to control the production of DBPs in chlorinated
swimming pools, managers should ensure that the pool is operated by fully
trained staff familiar with the various factors that affect pool water
chemistry and the actions to take when the water chemistry becomes out of
balance.

Kind Regards

Adrian Tinson, HMI health & safety, HSE, Entertainment & Leisure Sector

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Communications via the GSi may be automatically logged, monitored and/or
recorded for legal purposes.

Dear Mr McDermott

Uk pool operators are free to work to whatever standards they choose
provided they comply with UK health and safety law. However, to avoid
misunderstanding I reiterate that there is no legal requirement on
operators to meet the French standard.

Regards

Adrian Tinson
HMI health and safety, entertainment & leisure sector
0141 275 3060

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