Diesel Exhaust Particles (DEP) are released into the air when diesel fuel is burned by engines and pose a serious threat to the environment as well as to human life. Diesel exhaust is a complex mixture of gases, vapours, liquid aerosols and particulate substances that are the products of combustion. The main chemical components of diesel exhaust emissions are (1) gases and vapours like nitrogen, oxygen, water vapour and carbon dioxide, commonly found in the air. There are also hazardous gaseous chemicals like nitrous oxide, nitrogen dioxide, sulphur dioxide and carbon monoxide. And (2) fine particles termed as Diesel Particulate Matter (DPM) that include carbon particles with their core surrounded by trace metals, quinones, Volatile Organic Compounds (VOCs) and chemicals known as Poly Aromatic Hydrocarbons (PAHs) that adhere to their surface. The particulate matter can be fine or ultrafine, with 90% of particulate emissions considered to be fine, typically <1 μm in size. DPM can stay airborne for long periods of time, penetrate deep into the lungs and have high deposition rates in the airways because of their small size.
The National Institute of Occupational Safety and Health (NIOSH), National Toxicology Program, United Nation’s World Health Organization (WHO) have all separately classified DEP and DPM as carcinogenics to humans. In June 2012, the International Agency for Cancer Research (IARC) classified DEP (including DPM) as a known human carcinogen (Group 1). The Environmental Protection Agency (EPA) has put a myriad of regulations in place to limit the amount of emission from diesel vehicles. Tier 3 FTP Standards of the Supplemental Exhaust Emission Standards stipulate that manufacturers must certify vehicles to one of seven available “certification bins” and must meet a fleet average emission standard for their vehicle fleet in a given model year. They ultimately seek to control the amount per mile of particulate matter that a diesel engine is allowed to release into the air. The “certification bins” are classified by the Federal Test Procedure-75 or FTP-75. The FTP-75 is used for emission certification and fuel economy regulation in the United States. The lowest “certification bin” classification, 0, allows for 0 mg/mile of particulate matter released. The highest “certification bin” classifications, of a total of seven classifications, 160, allows only for 3 mg/mile of particulate matter released. Although these tests are designed for automobiles with diesel engines, they can be adjusted to include all types of vehicles. In Australia, the Australian Design Rules-37 (ADRs) are national standards for emissions under the Motor Vehicle Standards Act 1989.
Occupations with potential exposure to DEP/DPM include miners, construction workers, heavy equipment operators, bridge and tunnel workers, railroad operators, oil and gas and loading dock workers, truck drivers, material handling operators, farm labourers, long-shoring workers, and auto, truck and bus maintenance garage-workers. In Australia, miners are covered by the Mine Safety and Health Administration (MSHA) and workers in general industry, agriculture, construction and maritime industries are covered by the Occupational Safety and Health Administration (OSHA). Mine Safety and Health Administration (MSHA) laboratory testing establishes the level of DPM filtration required on specific diesel engines.