Monitoring and Assessment of Diesel Engine Exhaust Emissions

What are the Dangers of Diesel Engine Exhaust Emissions (DEEE) When diesel is combusted its incomplete combustion produces Products of Incomplete Combustion (PICs), along with several other products. These include inorganic gases such as carbon monoxide (CO), nitrogen monoxide (NO) and nitrogen dioxide (NO2) plus a myriad of hydrocarbons including aldehydes, aromatics and polycyclic aromatics hydrocarbons in a semi-volatile phase or bound with carbonaceous particulate. It is also possible for oxides of sulphur e.g. SO2, to be produced poor fuel quality is used. The Risk to Health? In the short-term exposure to diesel exhaust can cause coughing, irritation of the eyes, nose, throat, and respiratory tract. Furthermore, it can cause lung irritation and/or an allergic reaction causing asthma or making pre-existing asthma worse. Very high levels can lead to asphyxiation from carbon monoxide poisoning. ​ In the long-term exposure can lead to serious health effects. The World Health Organisations (WHO) “International Agency for Research on Cancer (IARC)” has classified diesel engine exhaust as carcinogenic to humans (Group 1), determining that exposure to diesel exhaust emissions increases the risk for lung cancer and possibly bladder cancer. DEEEs and the Law? The Employment Committee MEPs and the European Council have also introduced a new development to further lower the risks for workers exposed to carcinogenic and mutagenic substances. It has been agreed by European Commission negotiators that diesel fumes are added to the list of harmful substances and to set an occupational exposure limit of 0.05 mg/m³, calculated based on elemental carbon. ​ Currently DEEEs are regulated against through the general provisions of the COSHH Regulations 2002 (as amended) due to recognised hazardous substances (e.g. aromatics, PAHs, CO, NO and NO2). As such, it is required that exposure is prevented or, where this is not reasonably practicable, adequately controlled. Under COSHH there is no specific WEL associated with it, a precautionary approach to assessment and control is needed. It is further required under COSHH regulation 3, that the reduction of exposure to DEEE extends to non-employees (including members of the public) so far as is reasonably practicable. Hence, the use of diesel engines in the public transportation sector (road and rail) means that assessment of the risk be undertaken, and control measures put in place. ​ Monitoring and Assessing DEEEs? Due to the absence of a current set Workplace Exposure Limit (WEL) for DEEE, it is advisable to undertake an assessment of the components that pose the most significant risk, which means sampling for elemental carbon to 0.05mg/m3 and/or constituent gases such as carbon dioxide (CO2), carbon monoxide, Nitorgen monoxide (NO), nitrogen dioxide (NO2) and sulphur dioxide (SO2) be undertaken. Ideally personal monitoring of the elemental carbon and oxide gases should be taken from an employee’s breathing zone. As per any risk assessment, they must be representative of exposure during a working shift and include peak exposures. ​

As such, time series data is ideal, enabling the assessment of activities alongside average exposure values. Gaseous inorganic oxides can normally be assessed using a multigas monitor, such as the MultiRae Lite with sensors installed for CO, CO2, NO, NO2 and SO2 (If you wish to hire a diesel fume gas monitor please click here). The individual gases can be compared against their WELs and peak exposures used to indicate potential areas or times of concern. You must recognise that it is not possible to establish how far controlling exposure to the individual gaseous components to below their WELs will control the carcinogenic risk of poly-cyclic aromatic compounds, so elemental carbon analysis is also advisable. ​ To collect respirable elemental carbon, it is necessary to use take gravimetric samples using MDHS 14-4, “General Methods for the Gravimetric Determination of Respirable and Total Inhalable Dust.” As there is no WEL for DEEE particulate, a reference value of 0.15mg/m3 for EC has been used by HSE as indicative of ‘high’ EC exposure. However, with the new developments from the European Parliament it is advisable to work to 0.05mg/m3 of elemental carbon.

For further information on DEEEs please see go to: HSE - Diesel Engine Exhaust Emissions (DEEEs) INDG 286 – “Diesel engine exhaust emissions” HSG 187 – “Control of diesel engine exhaust emissions in the workplace” IOSH – “Diesel engine exhaust fumes: The facts”