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School of Physics Safety Manual
>12. Biological Hazards
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School of Physics Safety Manual
It is imperative that all personnel who deal with biological experimental procedures should be conscious of the possible hazards that may arise. If in doubt you must consult your veterinary or medical/clinical partners.
A bacteriological risk arises from any procedure which releases micro-organisms into the environment or which otherwise allows them access to the human body. Infection may be initiated by inhalation, ingestion, through the broken or unbroken skin, or the conjunctiva.
Many laboratory activities with fluids produce aerosols. When a fluid surface is broken large number of small droplets are produced. This may happen when a bubble bursts, when two solid surfaces separated by a film of liquid are parted, when one liquid is poured into another and when drops of liquid are allowed to fall on to a solid surface. The larger droplets fall to the ground, but the smaller ones evaporate rapidly and if the fluid contains bacteria these remain suspended as infected air-borne particles or droplet nuclei. The small particles, between 1 and 5 μm remain suspended for long periods and if inhale penetrate directly into the lung. Larger particles are removed in the upper air passages.
Aerosol production is dangerous not only to the operator but to all other persons in the vicinity. Even screw-capped bottles may present some hazards. A thin film of liquid may be present between the rim of the bottle and the rubber liner. When this film is broken by removing the cap aerosols are formed.
Gross contamination of surfaces and of clothing by spilled or broken cultures may result in infection by the hand-to-mouth route, to infection of existing skin lesions and to eye infections. The possibility of systematic infection by the conjunctival route must also be considered.
Direct ingestion is usually associated with mouth pipetting, failure to wash the hands, direct consumption of foods in the laboratory and smoking at the work bench.
Faulty techniques with hypodermic needles, and accidents with broken glass may lead to direct inoculation into the blood stream. Contamination of the skin with blood may lead to infection directly or through minor abrasions, e.g. Hepatitis B.
The ideal specimen container for pathological material must be easy and convenient to use by the patient and doctor without the outside being contaminated. It must be leak proof and virtually unbreakable: it should not create undue aerosol or spillage hazards when opened in the laboratory, and it should be easily sterilised, washed, or disposed of.
Screw-capped bottles may present some hazards (see Section 8.2.5). This risk is very much greater in containers that have ‘snap-on’ or ‘pop-up’ closures or bungs, or have ‘screw-in’ plugs. A larger film of liquid is easily trapped between the top of the container and the closure particularly after shaking in transit. It is very difficult to open these containers gently, as is possible with a screw-capped bottle; and the abrupt movement releases large amounts of aerosol and often a visible spray. These containers and many others in which any part of the closure is inside the tube may be dangerous and should not be used. Unfortunately they have become very popular for the collection of blood specimens for haematological and biochemical purposes. Hitherto these have been regarded as harmless, but a proportion of these samples is now known to contain Australia-Antigen.
Some screw-caps, particularly those made of plastic, seem to become loose spontaneously.
Sera sent from one laboratory to another should be dispatched in the smaller glass screw-capped (Bijou) bottles.
Hand basins with hot and cold running water must be provided in all laboratory rooms. There should be at least one basin in each room. In rooms where a large number of people work, e.g. more than 10, it is desirable that two basins be provided. The basins should be near to the doors. Ideally, taps should be operable without needing to use hands.
Automatic liquid soap dispensers should be avoided in favour of tablets of toilet soap regardless of the alleged economy of the former. Many of these dispensers must be operated by dirty or contaminated hands before they yield soap. It may not be obvious when they are empty.
Paper towels in dispensers are much more satisfactory than Turkish or huckaback towelling. These cloth towels are usually changed on a rigid time basis and may remain wet and dirty for long periods. Roller towels are acceptable only if they are of the continuous flow type and are properly maintained and promptly replaced.
As a general rule hands should be washed, preferably with a bactericidal soap, after completing any work and always before leaving the laboratory.
Individuals with medical conditions which predispose them to infection (eg eczema, compromised immune systems, diabetes etc) are at a special risk. Everyone must notify their supervisor of any illness or other medical condition that may compromise the immune system and may make them more susceptible to hazards, which may arise through working with micro-organisms.
Health surveillance is required under COSHH where:
Most biological agents (including bacterial and fungal spores) can be rendered non-viable by exposure to steam under pressure. The hazard from adequately treated material should be very low. Sterilisation depends on steam penetrating to all parts of the load. Lids must be removed and plastic bags undone. The efficiency of sterilisation should be verified by one of the following methods:
Disinfection is a less reliable means of sterilising materials than autoclaving. Disinfectants must be chosen carefully as there is no universal disinfectant, all have disadvantages. Disinfectants may deteriorate on standing or be inactivated by detergents, organic matter etc. and most are toxic or irritant. Some common types are listed below:
Chlorine releasing granules:
Clear soluble phenolics:
It is important that biological waste is disposed of safely. Appropriate sterilisation procedures must be used prior to disposal of any material contaminated with micro-organisms.
Material from the microbiology suite should then be placed in a yellow bag and taken to the yellow waste for incineration wheelie bin in the stores yard. Other autoclaved material such as large quantities of soils should be placed in a black bag and placed in the general waste wheelie bin.
Further guidance on standard operation procedures for waste disposal is given in Appendix 5 of The Management, Design and Operations of Microbiological Containment Laboratories.
There must be contingency plans for dealing with foreseeable emergencies. These could include spillage control, room evacuation, fumigation and decontamination and, if there is a risk of infection - first-aid and medical treatment (prophylazis) and health surveillance and counselling of exposed people.
Items required for dealing with spillages etc must be readily available and all workers must know the procedures. Guidance is given in Appendix 3 of The Management, Design and Operation of Microbiological Containment Laboratories.
In the event of an accident/incident/emergency, immediate steps must be taken to mitigate the consequences. Only people essential for carrying out repairs and other essential work may be permitted in the affected area and they must be provided with appropriate personal protective equipment and any necessary equipment or plant. Employees (or their representatives) must be informed as soon as practicable after an incident or accident that has (or may have) resulted in the release of a biological agent that could cause severe human disease. Employees must report such incidents or accidents forthwith.
If there is a risk of airborne infection the laboratory must be evacuated as quickly as possible. It may be necessary to fumigate the room before reoccupation.
People attending casualties should avoid becoming contaminated themselves.
Surveillance of exposed persons and possibly their close contacts may be required. Counselling may be necessary. If there is a health risk to the community there must also be contingency plans, made in consultation with local community physicians to limit spread:
The term “containment” describes the way in which biological agents are managed in the laboratory environment so as to prevent or control the exposure of laboratory workers, other persons and the outside environment to the agent(s) in question. This is achieved by a combination of measures.
Primary containment, ie, the protection of the worker and the immediate environment can be achieved through a combination of good microbiological practices/ techniques and the use of appropriate safety equipment, eg, microbiological safety cabinets. Further protection may be achieved through the use of appropriate immunisations, although this should be seen only as a useful supplement to reinforce procedural controls and the use of safety equipment, not the sole protective measure.
Secondary containment, ie, the protection of the people and the environment outside the laboratory can be achieved by a combination of laboratory design, engineering controls and operating procedures.
Containment measures must be reviewed at suitable, regular intervals and immediately if there is reason to suspect that the measures are no longer adequate or, if in the light of new scientific or technical knowledge, the assessment is inadequate. Laboratory containment measures must reflect the nature and severity of the biological hazard; an outline guide is provided in the table below.
Laboratory Containment Level
Where used, be aware that there is a legal requirement to check these cabinets for operation and containment. High Efficiency Particulate Air (HEPA) filters used in microbiological safety cabinets are to be checked by a professional engineer twice per year, and the potassium iodide test is performed annually. Class 1 Safety Cabinets minimize escape of aerosols by drawing air in through the open front. The air passes through a high efficiency particulate air (HEPA) filter and is then discharged (usually to the outside). These cabinets protect the worker but not the work.
There is a device (anti-blow back valve) to prevent back flow of air if the fan fails. Class 2 Safety Cabinets are designed such that air is drawn through the open front of the cabinet, but instead of going upwards, it is drawn downwards through grills in the base of the cabinet. The air passes up the back of the cabinet and is HEPA filtered. A proportion is vented (again normally to the outside) while the rest is re-circulated downwards through the working area providing a curtain of filtered air. These cabinets protect both the worker and the work from contamination and are particularly useful for handling cell cultures. Class 3 and Class 1/3 Safety Cabinets provide a totally enclosed working area and the operator wears long rubber gloves which are attached to the front panel. Incoming air is HEPA filtered once and outgoing air twice. Both work and worker are protected but this type of cabinet is normally only necessary in Containment Level 3/4 laboratories. Laminar Flow Cabinets may be used for preparing media and pouring plates only. They can be horizontal or vertical flow type. With these cabinets, the direction of flow is outwards towards the worker providing a sterile working environment for procedures such as plate pouring only. Because of the outward flow of air there is no protection for the worker and therefore these cabinets must not be used for handling any pathological materials or cultures of any micro-organisms.
Any animals should be kept in suitable housing to which only authorised persons have access. Any laboratory animal, whether stock or experimental, may excrete an infectious agent in its faeces, urine, saliva or expired air. Infection of handlers is also possible by direct transmission during handling; from bites and scratches, from contact with or inhalation of dust from cages and bedding; and from contact with blood or with tissues removed at autopsy.
Infected animals may not be obviously ill; infections may be subclinical. Therefore all laboratory animals at all stages of their progress through an animal house must be treated as potentially infectious. Anyone bitten by an animal should be treated by a medical officer.
RID Regulations concerning the International Carriage of Dangerous Goods by Rail
The Carriage of Dangerous Goods and Use of Transportable Pressure Equipment Regulations 2004 (SI 568) as amended
The Merchant Shipping (Dangerous Goods and Marine Pollutant) Regulations 1997 (SI 2367)