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Diesel particulate matter (DPM) is the term that is used to describe fine particles produced by exhaust from diesel engines. Diesel exhaust emissions can be in two phases, either gas or particulate where each contains both organic and inorganic components (EnviroMail #84: September 2014). The particulate phase of diesel exhaust includes clusters of respirable particles (i.e., particles small enough to  be inhaled into the lungs) that are composed mainly of carbon atoms. These respirable particles of carbon  are termed “diesel particulate matter” (DPM).

Why do we measure DPM?

The Handbook on Mine Occupational Hygiene Measurements clearly indicates that the primary purpose for measuring the workers exposure to DPM is to protect worker health by ensuring the level of exposure is as low as reasonably practicable. Measurements are also conducted to check the compliance with relevant Occupational Exposure Limits (OELs) or standard.

Health effects of DPM

Sensory irritations and respiratory symptoms

These involve irritation of the eyes, nose, and throats

Immunologic effects (allergenic responses and asthma-like symptoms).

Inappropriate change in the structure or function of the immune system.

Premature death from cardiovascular, cardiopulmonary, or respiratory causes

Death that occurs before a person reaches an expected age such as 75.

Lung cancer

Uncontrolled growth of abnormal cells which may start either from one lung or both lungs.

Choice of analyte

According to Chapter Q of the NIOSH Manual for Analytical Methods, where there is a mixture of compounds involved, as in this case of DPM, a surrogate must be identified to determine the toxicity. DPM is predominantly and typically 80% of carbon element usually contains 30% - 90% of this carbon. Organic carbon (OC) is not used to measure exposure because other sources of OC such as cigarette smoke and other combustion aerosols are common or often encountered in the workplaces. Elemental carbon was identified as the surrogate for DPM because it is a more selective measure of particulate DPM or more sensitive to DPM and usually contains 30% - 90% of this carbon. According to a position paper for DPM updated in July 2013 by the Australian Institute of Occupational Hygienists Inc (AIOH), the irritant effect decreases markedly when workplace exposures are controlled below 0.1 mg/m3 DPM (as proposed elemental carbon).