5.2 Assessment and control of risk

Question 1

Biological infections must be reported to the enforcing authority only when

Answer 1

an
employer has been notified by a doctor, in writing, that an employee is suffering
from one of the infections listed in Schedule 3 of RIDDOR, which is linked to the
corresponding activity.

Question 2

Biological agents are classified into four hazard groups according to: 4

Answer 2

 Their ability to cause infection
 The severity of the disease that may result
 The risk that infection will spread to the community
 The availability of vaccines and effective treatment.

Question 3

The four groups of biological agents and their accompanying descriptions

Answer 3

1 Unlikely to cause human disease.
2 Can cause human disease and may be a hazard to
employees. It is unlikely to spread to the community and
there is usually effective prophylaxis* or treatment available.
3 Can cause severe human disease and may be a serious
hazard to employees. It may spread to the community, but
there is usually effective prophylaxis* or treatment available.
4 Causes severe human disease and is a serious hazard to
employees. It is likely to spread to the community and there
is usually no effective prophylaxis* or treatment available

Question 4

Knowing the HG alone is not sufficient for risk assessment purposes. Although the
hazard group of the agent is based on some of its hazardous properties, it is not a
complete picture, for example:

Answer 4

it does not address the route(s) of transmission that
may influence the risk assessment, in terms of deciding whether additional control
measures are required.

Question 5

There are three ways in which you might be exposed to biological agents at work:

Answer 5

1) Exposure as a result of working with biological agents, for example: in a
microbiology laboratory.
2) Exposure which does not result from the work itself but is incidental to it, mainly
because biological agents are present as contaminants, for example: farming,
refuse collection, sewage treatment.
3) Exposure, which is not a result of the work that is done, for example: catching
flu from a work colleague.
Note: Only the first two categories are covered by CoSHH.

Question 6

Biological organisms have a number of strategies for making the leap to a new
host, including:

Answer 6

 Droplet transmission: for example, being passed along when one host
accidentally sneezes on another. The flu is transmitted this way.
 Airborne transmission: for example, being exhaled by one host and inhaled
by another. Tuberculosis is transmitted this way.
 Vector transmission: getting picked up by a carrier (the vector, such as a
mosquito) and carried to a new host. Malaria is transmitted this way.
 Waterborne transmission: leaving one host (in faeces, for example), infecting
the water supply, and being taken up (in drinking water, for example) by a new
host. Cholera is transmitted this way.
 ‘Sit-and-wait transmission’: being able to live outside a host for long periods
of time until coming into contact with a new host. Smallpox can survive for years
outside of a host.

Question 7

Most micro-organisms have a particular route of entry, but in some cases infection
can occur by more than one route.
Occupational examples of infection are:

Answer 7

 Putting contaminated hands and fingers (or pens etc.) into the mouth, nose or
eyes.
 Breathing in small infectious droplets (aerosols) from the air.
 Splashes of blood and other body fluids into the eye and other mucous
membranes, such as the nose and the mouth.
 Broken skin if it comes into direct contact with the micro-organism (or something
contaminated by micro-organisms).
 A skin-penetrating injury, for example: via a contaminated needle or other
sharp.

Question 8

Zoonoses are diseases that:

Answer 8

 can be transmitted from animals to humans

 may cause ill health in humans but may not cause ill-health in animals.

Question 9

Human activity is involved with many emerging infectious diseases, for example:
environmental change enabling a parasite to occupy new niches or hosts. Several
human activities have led to the emergence and spread of new diseases: 4

Answer 9

 Encroachment on wildlife habitats: the construction of new villages and
housing developments in rural areas force animals to live in dense populations,
creating opportunities for microbes to mutate and emerge.
 Changes in agriculture: the introduction of new crops attracts new crop pests
and the microbes they carry to farming communities, exposing people to
unfamiliar diseases.
 Uncontrolled urbanisation: the rapid growth of cities in many developing
countries tends to concentrate large numbers of people into crowded areas with
poor sanitation. These conditions foster transmission of contagious diseases.
 Modern transport: ships and other cargo carriers often harbour unintended
‘passengers’ that can spread diseases to faraway destinations. While with
international jet-airplane travel, people infected with a disease can carry it to
distant lands, or home to their families, before their first symptoms appear.

Question 10

Hierarchy of control

The methods chosen to control the risks identified by the CoSHH biological agent
risk assessment should follow the hierarchical approach which is common to both
MHSWR and CoSHH. The hierarchy reflects the fact that eliminating and controlling
risk by using physical engineering controls is more dependable than relying on
systems of work:

Answer 10

 Eliminating risks: for example: by substituting a hazardous biological agent with
something less/non-hazardous, such as using a non-toxigenic strain of a
biological agent when carrying out laboratory quality control tests.

 Controlling risks at source: by using engineering controls and giving collective
protective measures priority, for example: using a microbiological safety cabinet
when work could create an infectious aerosol, or using needle safety devices to
prevent and control needle-stick injuries.

 Minimising risks by designing suitable systems of working, for example: having
an effective hand hygiene policy in place. This option also includes the use of
personal protective clothing and equipment (PPE), but PPE should only be used
as a last resort after considering elimination or tackling at source.

Question 11

Any control strategy would include consideration of the following specific hierarchy of
control for biological agents: 15

Answer 11

  eradication 
  reduced virulence 
  change work method or suppress generation of aerosols 
  isolation and segregation 
  containment (CoSHH Schedule 3) 
  control for specific examples 
  sharps control 
  immunisation 
  decontamination and disinfection 
  effluent and waste collection 
  storage and disposal (controlled) 
  personal hygiene measures 
  PPE 
  biohazard signs 
  baseline testing and health surveillance.

Question 12

Immunisation

CoSHH requires that employees should be given a vaccination if the risk
assessment shows:

Answer 12

 there is a risk of exposure to a specific biological agent
 there is an effective vaccine
 the employee is not already immune.

Question 13

Healthcare research laboratory

An example of the above measures applied to a workplace setting is a health care
research laboratory requiring level 3 containment. The following control measures
would be required:

Answer 13

Technical measures
 The separation of the laboratory from other activities in the same building.
 Extracted air to be passed through a HEPA (high efficiency particulate air) filter.
 Access via an airlock to be restricted to authorised persons by means of a
security pass or swipe card.
 The workplace to be sealable to permit disinfection and to be maintained at an air
pressure negative to atmosphere.
 All surfaces to be impervious to water, easy to clean and resistant to acids,
alkalis, solvents and disinfectants.
 Secure storage to be provided for the biological agents.
 An observation window to be fitted so that the occupants can be seen at all times.
 A class 3 microbiological safety cabinet with sealed front and glove port access to
be used to carry out the work.
 A facility such as an autoclave to be provided for rendering waste safe.
 The provision of appropriate and adequate washing and toilet facilities.

Procedural controls
 Written procedures for safe handling of potentially infectious samples.
 Use of PPE, such as face visors, gloves, etc.
 Training.