Identification and assessment of the risk

Question 1

A suitable and sufficient assessment must be carried out to identify and
assess the risk of exposure to legionella bacteria from work activities and
water systems on the premises and any precautionary measures needed. The
dutyholder is responsible for ensuring the risk assessment is carried out. The
dutyholder is either:

Answer 1

(a) the employer, where the risk from their undertaking is to their employees
or others; or
(b) a self-employed person, where there is a risk from their undertaking to
themselves or others; or
(c) the person who is in control of premises or systems in connection with
work, where there is a risk from systems in the building, eg where a
building is let to tenants, but the landlord keeps responsibility for its
maintenance.

Question 2

The risk assessment should identify and evaluate potential sources of
risk and:

Answer 2

(a) the particular means of preventing exposure to legionella bacteria; or
(b) if prevention is not reasonably practicable, the particular means of
controlling the risk from exposure to legionella bacteria.

Question 3

Before any formal health and safety management system for water systems is
implemented, the dutyholder should carry out a risk assessment to identify the
possible risks. The purpose of the assessment is to enable a decision on:

Answer 3

(a) the risk to health, ie whether the potential for harm to health from exposure is
reasonably foreseeable, unless adequate precautionary measures are taken;
(b) the necessary measures to prevent, or adequately control, the risk from
exposure to legionella bacteria.

Question 4

There are a number of factors that create a risk of someone acquiring
legionellosis, such as:

Answer 4

(a) the presence of legionella bacteria;
(b) conditions suitable for growth of the organisms, eg suitable water temperature
(20 °C–45 °C) and deposits that are a source of nutrients for the organism,
such as sludge, scale, rust, algae, other organic matter and biofilms;
(c) a means of creating and spreading breathable droplets, eg the aerosol
generated by cooling towers, showers or spa pools;
(d) the presence (and numbers) of people who may be exposed, especially in
premises where occupants are particularly vulnerable, eg healthcare,
residential and nursing homes.

Question 5

The following list contains some of the factors to consider, as appropriate,
when carrying out the risk assessment:

Answer 5

(a) the source of system supply water, eg whether from a mains supply or not;
(b) possible sources of contamination of the supply water in the premises before
it reaches the cold water storage tank, calorifier, cooling tower or any other
system using water that may present a risk of exposure to legionella bacteria;
(c) the normal plant operating characteristics;
(d) unusual, but reasonably foreseeable operating conditions, eg breakdowns;
(e) any means of disinfection in use;
(f) the review of any current control measures;
(g) the local environment.

Question 6

The record of the assessment is a living document that must be reviewed to
ensure it remains up-to-date. Arrange to review the assessment regularly and
specifically whenever there is reason to suspect it is no longer valid. An indication
of when to review the assessment and what to consider should be recorded. This
may result from, eg:

Answer 6

(a) changes to the water system or its use;
(b) changes to the use of the building in which the water system is installed;
(c) the availability of new information about risks or control measures;
(d) the results of checks indicating that control measures are no longer effective;
(e) changes to key personnel;
(f) a case of legionnaires’ disease/legionellosis associated with the system.