Research has indicated that the particulate component of the diesel engine exhaust has the potential to induce various health effects and has been classed as a probable human carcinogen. At present in the UK there
are no workplace exposure limits for diesel engine exhaust emissions (DEEEs). However, under the Control of Substances Hazardous to Health regulations (COSHH) and the The National Institute for Occupational Safety and Health (NIOSH), DEEEs are classed as a substance hazardous to health and as such it is recommended that employers prevent or reduce workers exposure as much as is reasonably practicable.
Widespread use of larger diesel powered equipment has resulted in the exposure of a large number of workers to the complex mixtures of DEEEs produced by combustion. The major constituents are:
Oxides of Nitrogen
Oxides of Sulphur
Polycyclic Aromatic Hydrocarbons
The quantity and composition of DEEEs are dependent on:
The type of engine
Whether the engine has been regularly maintained
The type of fuel used
Whether the engine is working to its capacity
The engine temperature
Potential for exposure to diesel particulate and toxic fumes exists whenever workers are in close proximity to operating diesel equipment. In many cases the fact that the equipment is operating in the open environment significantly reduces the potential for excessive exposures. Conversely, where diesel vehicles and equipment are used in confined areas (e.g. underground mines,ships' holds,tunnels) there is a significant risk of exposure.
The gaseous phase of diesel exhaust consists largely of the same gases found in air, such as nitrogen, oxygen, carbon dioxide and water vapour.
The particle fraction of diesel exhaust consists mainly of very small particles which can reach the deep parts of the lungs. When clumped together the particles consist of an irregular stacked graphitic structure referred to as elemental carbon. The graphitic nature and high surface area of these particles means they have the ability to absorb hundreds of organic substances (organic carbon) originating from the unburned fuel, lubricating oils and the compounds formed in the complex chemical reaction during the combustion cycle.
Deciding which components of the DEEEs to monitor for in order to provide a representative measure of exposure can be difficult. One method considered by many to be the most appropriate to use involves sampling onto a thermally treated quartz filter using a respirable cyclone sampler. Sample analysis on the captured aerosol is best conducted using NIOSH method 5040 for determination of organic carbon (OC) associated with the organic substances and elemental carbon (EC) from the soot. Elemental carbon provides a good surrogate measure of exposure to DEEEs for the following reasons:
In most workplace environments the only source of airborne particulate elemental carbon is from DEEEs. Coal mines are an exception and a size selective samplers called a precision-jewelled impactor needs to be used to overcome the problems with discerning between the larger EC particles from coal dust and the sub micron EC particles from diesel particulate.
It is believed that the fine elemental carbon particles associated with diesel particulate is the primary cause of health problems associated with long term exposure of DEEEs
Diesel particulate once airborne behaves like a gas and stays airborne for a long time. As such, elemental carbon is fairly representative of the other gases and vapours associated with DEEEs.
Scientific Analysis Laboratories can offer a comprehensive range of analysis from Diesel Exhaust Emissions:
Elemental and Organic Carbon
Nitric Oxide and Nitrogen Dioxide
Polycyclic Aromatic Hydrocarbons
For further information, please contact Duncan Campbell at the Head office.