The World Health Organisation (WHO) has declared that diesel engine exhaust emissions can cause cancer in humans.They say DPM belongs in the same potentially deadly category as asbestos, arsenic and mustard gas.
After a week-long meeting, the International Agency for Research on Cancer reclassified diesel exhaust emissions from its group of probable carcinogens, to its group of substances that has definite links to cancer.
The World Health Organisation (WHO) says diesel engine exhaust emissions cause lung cancer and increase the risk of bladder cancer.
The WHO decision was unanimous and based on “compelling” scientific evidence.
There are many reports and papers that have been submitted on this subject from multiple sources.
As another example, and based on the available information, the Australian Institute of Occupational Hygienists believes that worker exposure to DPM levels should be controlled to below 0.1 mg/m3 as an 8 hour time weighted average value, measured as submicron elemental carbon.
The value has been determined as being a balance of the factors such as primarily minimising eye and respiratory irritation, then secondarily minimising any potential for risk of lung cancer to a level that is not detectable in a practical sense in the work force, and finally on providing a level that is achievable as best practice by industry and government.
Potential for exposure to potentially life threatening diesel Particulate Matter – DPM 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.
Where diesel equipment is operating in confined areas (eg underground mines, tunnels, ships’ holds, cool rooms, and large truck loading and unloading depots) there is a significant risk of exposure.
Levels in Australian underground coal mines have been measured at 0.01 to 0.37 mg/m3 (as EC) (Joint Coal Board, 1999; Rogers, 2005), although levels up to 2.2 mg/m3 have been measured, depending on job type and mining operation (Pratt et al., 1997).
A working group of the International Agency for Research on Cancer (IARC) Monograph Series reviewed the scientific evidence regarding the carcinogenicity of diesel engine exhaust (DEE).
The Working Group concluded that DEE is a cause of lung cancer (Group 1: carcinogenic to humans) based on human, animal, and experimental evidence (Benbrahim-Tallaa et al. 2012).
Given that large populations of workers are exposed to DEE in the workplace and that urban populations are exposed to low levels of DEE in the ambient environment, the potential public health impact of DEE exposure may be considerable.
For example, Rushton et al. (2012) recently estimated that occupational DEE exposure in the United Kingdom was the third most important occupational contributor to the lung cancer burden after asbestos and silica exposure.
The Australian Medical Association declared in its March 2013 Submission to the Senate Standing Committee on Community Affairs on the Inquiry into the impacts on health of air quality in Australia that particulate matter from Motor vehicle emissions (particularly diesel engines), industry emissions, mining activity, agricultural practices, and other sources produced known health effects including Upper respiratory tract irritation and infection; exacerbation of asthma; decreased lung function; exacerbation of, and increased mortality from, cardiorespiratory diseases; myocardial infarction; premature mortality; atherosclerosis; adverse birth and neurodevelopment outcomes.
The National Environment Protection Council’s Summary for Policy Makers of the Health Risk Assessment on Air Pollution in Australia (Report – Nov 2013 ) declared particulate matter as a major contributor associated with health concerns.
Over the past 100 plus years since the invention of a compression ignition engine by Rudolph Diesel, it has contributed significantly to the productivity of many nations, owing to the widespread use of larger diesel powered equipment in most industrial activities.
The down side in terms of occupational health has been the exposure of a large number of workers to the complex mixture of toxic gaseous, adsorbed organics and particulate components found in the raw exhaust emissions.
The physical and chemical conditions that exist inside any most diesel engines under any conditions differ considerably from spark-ignition engines, because, by design, diesel engine power is NOT controlled by the air/fuel mixture (as in most PETROL engines), but rather it is directly controlled by the fuel supply.
For instance, diesel engines generally produce 28 times less carbon monoxide than petrol engines, as diesels burn their fuel in excess air even at full load. However, the lean-burning nature of diesel engines and the high temperatures and pressures of the combustion process result in significant production of gaseous nitrogen oxides – an air pollutant that constitutes a unique challenge with regard to their reduction.
The fine particulate matter also known as DPM from diesel engine exhaust emissions (e.g., soot, sometimes visible as opaque black dark-coloured smoke) has traditionally been of greater concern, as it presents different health concerns and is rarely produced in significant quantities by petrol engines.
Diesel engine exhaust emissions have been known for their characteristic odours, which changed when the sulphur content of diesel fuel was reduced, and again when catalytic converters were introduced in exhaust systems.
The particulate fraction of the diesel exhaust emissions consists of a solid carbon phase and ultra-fine droplets of a complex mix of semi-volatile organic compounds.
The solid particulate fraction consists mainly of very small particles (typically 15 30 nm diameter) that rapidly agglomerate together to form “chains” or clumps of particles.
High-resolution electron microscopy has demonstrated that the basic diesel particle consists of an irregular stacked graphitic structure, nominally called elemental carbon.
The graphitic nature and high surface area of these very fine carbon particles means they have the ability to absorb significant quantities of hydrocarbons (the semi-volatile organic carbon droplets and vapours) originating from the unburned fuel, lubricating oils and the compounds formed in the complex chemical reaction during the combustion cycle.
In terms of health outcome, the very small particle size of DPM is important as this means it can reach the deep parts of the lungs. Particulate overload rather than chemical composition is thought to be the major mechanism leading to toxic effect.
In 1988 the US National Institute of Occupational Safety and Health (NIOSH) published Criteria Bulletin No.50 (NIOSH, 1988) which proposed a potential link between occupational exposure to diesel exhaust and lung cancer.
The NIOSH finding was based on the consistency of toxicological studies in rats and mice and limited epidemiological evidence, mainly from railroad workers.
The IARC evaluation 2A (probable human carcinogen) was based on limited evidence in humans and sufficient evidence of carcinogenic risk in animal studies (IARC, 1989).
The Health Effects Institute (HEI, 1995) undertook a review of the toxicological studies including acute and chronic effects (such as risk of lung and other cancers). It also included the 30 epidemiological studies of workers exposed to diesel emissions in occupational settings for the period 1950 to 1980.
About half of these epidemiological studies indicated an increase risk of lung cancer and the remainder showed no increase in lung cancer risk. HEI after examining the positive outcome studies concluded that the epidemiological data indicated weak associations between exposure to diesel exhaust and lung cancer with a relative risk of 1.2 to 1.5. They issued a note of caution indicating that all of the studies lacked definitive exposure data for the populations studied and most had an inability to determine the influence of confounding factors, such as tobacco smoking.
Mines Safety and Health Administration (MSHA, 2001) reviewed 47 epidemiological studies and determined that in 41 studies there was some degree of association between occupational exposure to diesel particulate matter and an excess prevalence of lung cancer. However, some of these studies had limited statistical power either because they included relatively few workers or had an inadequate allowance for latency or follow up period. MSHA then concluded, based on the studies with positive lung cancer outcomes and implied estimates of historical exposure levels, that exposure at a mean concentration of 0.64 mg/m3 DPM for a period of 45 years would result in a relative risk of 2.0 for lung cancer.
Source – Australian Institute of Occupational Hygienists.
For more information please click on these links to read these associated articles and papers.
Specific references used in the production of this position statement include:
AIOH (2007). Position paper – Diesel Particulate and Occupational Health Issues, May 2007.
Brown, AM et al. (1997). The Occurrence of Cancer in a Cohort of New South Wales Coal Miners. Aust & NZ J Public
Health 21(1) 29-32. Dabill, DW (2004). Controlling and monitoring exposure to diesel engine exhaust emissions in non-coal mines. Health and Safety Laboratory Research Report 252 for the UK HSE (see http://www.hse.gov.uk/research/rrpdf/rr252.pdf). Davies, B & A Rogers (2004). A guideline for the evaluation and control of diesel particulate in the occupational Environment. Australian Institute of Occupational Hygienists, Inc PO Box 1205, Tullamarine Victoria 3043 Australia ISBN 0 9577703 5 9. Groves, J & JR Cain (2000). A Survey of Exposure to Diesel Engine Exhaust Emission in the Workplace. Ann Occup Hyg 44: 435-447. Hedges, K, et al, (2007). Diesel Particulate Matter in Underground Mines – Controlling the Risk, Proceedings The AusIMM New Leaders Conference 2-3 May 2007. HEI (1995). Diesel exhaust: a critical analysis of emissions, exposure and health effects. A special report of the Institute’s Diesel Working Group, April 1995. Cambridge, MA: Health Effects Institute.
HEI (2009, 2012 & 2013). A series of Research Reports specific to Diesel Particulate available on www.healtheffects.org IARC (1989). IARC monograph on the evaluation of carcinogenic risk of chemicals to humans: diesel and gasoline engine exhaust and some nitroamenes. Vol 46. Lyon, France: International Agency for Research on Cancer. IARC (2012). Press Release #213, Diesel Engine Exhaust Carcinogenic, June 2012.
Joint Coal Board (1999). Diesel Particulate in Coal Mines (1st Edition) – Questions & Answers. The Joint Coal Board 1999 (Australia, NSW). Liukonen, LR, et al. (2002). Diesel Particulate Matter Exposure to Railroad Train Crews. Am Indust Hygiene Assoc J 63 September/October); 610-616.
MSHA (2001). Mine Safety and Health Administration 30 CFR part 57 Diesel Particulate Matter Exposure of Underground Metal and Nonmetal Miners; Final Rule, US Federal Register January 19, 5706-912.
NCI (2010). Stewart, P, et al. The Diesel Emissions in Miners Study: I Overview of the Exposure Assessment Process, Ann Occup Hyg 54:728-746, 2010. Coble, J, et al, II Exposure Monitoring Surveys and Development of Exposure Groups. Ibid 747-761, 2010. Vermeulen, R, et al, III Interrelationship between Respirable Elemental Carbon and Gaseous and Particulate Components of Diesel Emissions from Area Sampling in Underground non-metal Mining Facilities, ibid 762- 773, 2010. Vermeulen, R, et al. IV Estimating Historical Exposures to Diesel Emissions in Underground Non-metal Mining Facilities, ibid 774-778, 2010. NCI (2012): Attfield, et al, The Diesel Emissions in Miners Study: A Cohort Mortality Study with Emphasis on Lung Cancer. J Natl Cancer Inst 104: 2012 and Silverman, et al, The Diesel Exhaust in Miners Study: A Nested Case-control Study of Lung Cancer and Diesel Exhaust, JNCI 104: 2012. NIOSH (1988). Carcinogenic effects of exposure to diesel exhaust. Current Intelligence Bulletin 50, August 1988. NIOSH (2003). Diesel particulate matter (as elemental carbon) and appendix Q. NIOSH Manual of Analytical Methods, Fourth Edition, NIOSH Publication 2003-154. NSW Department Primary Industries (2008). Guideline for the Management of Diesel Engine Pollutants in Underground Environments -MDG-29 Mine safety Operations Division, April 2008. Pratt, SL, et al. (1997). Evaluation and Control of Employee Exposure to Diesel Particulate at Several Australian Coal Mines. Appl. Occup. Environ. Hygiene 12(12); 1032-1037.
DPM POSITION PAPER PAGE 13 OF 13 I FIRTH | 09.07.2013 Qld Department Natural Resources and Mines (2012). Shift Adjustment of the Guideline Limit for Diesel Particulate Matter, Safety Bulletin No. 127, 24 December 2012.
Rogers A (2005). Exposure Measurement and Risk estimation from Diesel Particulate Exposures in Underground Coal Mines. Research Project No 20000, Joint Coal Board Health & Safety Trust.
Rogers, A & Davies, B (2001). Diesel Particulate (Soot) Exposures and Methods of Control in Some Australian
Underground Metalliferous Mines. Short Course Notes Presented at the AIOH 19th Annual Conference, 1st – 5th
December 2001; Australian Institute of Occupational Hygienists (AIOH). Rogers, A & B Davies (2005). Diesel Particulate – Recent Progress on an Old Issue. Ann. occup. Hyg 49:453-456. Rogers A & B Davies (2013). Diesel Exhaust Emissions – Where are we Know? Notes Presented at the AIOH Seminar Series, March 2013. US EPA (2002). Health assessment document for diesel engine exhaust. US Environmental Protection Agency, Document EPA/600/8-90/057F May 2002. WA Department of Mines and Petroleum (2013). Managing Diesel Emissions in Underground Mines – Guideline, Resource Safety 2013.