GATHER INFORMATION - IDENTIFY THE RISKS
When planning a scheme of work, the objective is usually some end product and being able to obtain it in the most cost-effective or most convenient way. There may be some consideration of safety but this is not always the case. When planning some work that involves the use of hazardous materials at work, there should be consideration of:
The substances used in or formed through the planned work
The process - the way in which the work will be carried out
The scale of the process
Instances, type and extent of potential exposure
Waste products and their disposal
In the workplace, hazardous substances are defined as substances that are dangerous to health and are:
Used in the normal course of work including those kept in store
Released because of the work including those that are leaked or spilled and those forming fumes, vapours and aerosols
Produced through the work, including waste materials and residues
Read more about GATHERING INFORMATION
An Illustrative Example: Using Aluminium Powder to Reveal Fingerprints
Following a domestic burglary, a crime scene examiner attends the property with the purpose of recovering fingerprints. Aluminium powder, frequently used to reveal prints on non-absorbent surfaces, is to be used, so we need to evaluate the nature of any hazards and the risks to exposure in the use of aluminium powder.
Skip this part and go directly to Step 2 of the COSHH assessment
SAFETY DATA FOR ALUMINIUM POWDER
To discover whether or not aluminium powder is a hazardous substance, we need to consult widely (see collecting information). We will discover from the material safety data sheet that aluminium powder is indeed a hazardous substance.
The material safety data sheet for aluminium powder (supplied by Eckart Pigments, 2008) reveals the following significant hazards can be expected by anyone that uses the powder. (the MSDS will open in new window as an Adobe Acrobat file)
Aluminium Powder (stabilised)
To enhance latent fingerprints
CAS Number - Chemical Abstract Service registry number
The aluminium powder is to be applied using a Zephyr brush, made from very fine, glass filaments. The tip of the bundle of filaments is first dipped into a small bottle containing the powder until sufficient has been loaded onto the fibres. The brush is then "twizzled" over the print-bearing surface.
The filaments become widely separated and the powder becomes both deposited on the surface and dispersed into the air. Ideally, little of the powder becomes dispersed, but usually this is not the case, much depending on the skill of the operator in the process.
THE SCALE OF THE PROCESS
The amount of powder used may well be only a few milligrams at any one location within the crime scene. However, a crime scene examiner will use aluminium powder on a frequent basis at a very large number of scenes over an extended period. It is appropriate therefore to consider that consumption of aluminium powder and the potential for prolonged exposure to be significantly greater than for a one-off occasion at just one crime scene.
Being aware of the types of exposure that are possible at any stage of a process is a prerequisite to minimising the exposure, particularly if the substances are hazardous. Exposure to aluminium powder could occur through any of: a) direct contact with the skin or eyes, b) inhalation of the dispersed particles, c) ingestion, and d) injection, for example, through a cut. The extent of exposure will depend on whether or not the examiner uses appropriate forms of protective clothing (e.g., scene suit, gloves, mask and goggles). Can exposure to aluminium powder be completely prevented? Probably not, but it will certainly be possible to reduce exposure to safe levels.
WASTE PRODUCTS AND THEIR DISPOSAL
There is no waste material or by-product in this process. However, if the examiner is required to clean the scene using say, proprietary chemical wipes, these too should be included in any assessment of risks. We will assume here that the housholder will wipe the dusted surfaces clean using a household detergent.
Section 2 - Hazards Information
F Highly flammable
R 10 Flammable
R 15 Contact with water liberates extremely flammable gases
Section 7 - Handling and Storage
Dust can combine with air to form an explosive mixture
Reaction with water liberates extremely flammable gas (hydrogen)
Section 8 - Exposure Contol
A limit is set on the permissible maximum long term exposure to the dust:
Long-term value: 10*; 4** mg/m³
*total inhalable dust **respirable dust
Inhalable dust is dust which enters the body, but is trapped in the nose, throat, and upper respiratory tract
Respirable dust is airborne material which is capable of penetrating to the gas-exchange region of the lungs
Section 10 - Stability and Reactivity
Avoid dust clouds, they may form explosible dust-air-mixture
Contact with water may release flammable gases
Section 11 - Toxicological Information
Primary irritant effect:
On the skin: No irritant effect
On the eye: No irritating effect
Sensitization: No sensitizing effects known
Subacute to chronic toxicity: No effects known
Aluminium powder clearly possesses several properties which make it a hazardous substance. Apparently, it will react with water to form hydrogen, a highly flammable gas; the dust can form explosive mixtures with air; and there is a safe limit placed on how much dust can be inhaled. On the other hand, the substance (aluminium) itself is not known to be an irritant to the skin or eyes, or be otherwise toxic.
The risks appear to include:
The possibility of explosion
The possibility of flammability
The possibility that the operator will experience dust-induced irritation
Dangerous Substances and Explosive Atmospheres Regulations
The DSEAR require an assessment of substances or mixtures of substances that are flammable, highly flammable, extremely flammable and explosive. Aluminium powder does exhibit these characteristics. However, as we shall see later, the quantities of the powder in use at any instant are trivial, or carried with a fingerprint kit, very small. For this reason, assessment under DSEAR will not be necessary, this COSHH assessment being suitable for purpose.