“…inhalation and deposition of SOA and mineral dust can also lead to the release of ROS, which may contribute to oxidative stress”
Atmospheric particulate matter refers to the microscopically small solid particles or liquid droplets that remain suspended in the air for extended periods of time. It comprises a wide variety of substances, such as dust, soot, smoke, aerosols, and fumes, and is typically classified according to size: coarse (diameter >2.5 mm); fine (diameter <2.5 mm); or ultrafine (diameter <0.1 mm). Although much of the particulate matter occurs naturally, eg, from volcanoes, dust storms, forest fires, there is also a significant man-made contribution, for example from the burning of fossil fuels.
Many studies have reported the detrimental effects of airborne particulate matter on our health, such as lung irritation and inflammation, reduction of airway function in people with chronic lung diseases. In turn, these effects can cause changes in blood chemistry, which can result in clots and increase the risk of heart attack, or result in the release of chemicals that can impair heart function. The smaller the particles, the deeper they can penetrate into the respiratory system and the more hazardous they are to breathe.
In addition, the particulate matter can be carried over long distances by the wind and cause widespread environmental damage. The nature of the damage varies according to the precise chemical composition, but may include reductions in forest health, soil quality and ecosystem diversity and increased water acidity. Furthermore, it has been implicated in climate change.
Airborne particulate matter is thus a matter of global importance and, consequently, research into it has been growing extensively. This has been further accelerated by advances in the technologies available for measuring and quantifying the different components of atmospheric particles and studying their individual physical properties and the chemical interactions that occur between them. However, the relative importance of the different chemical components of airborne particulate matter and the magnitude of their overall effects in terms of both climate and health have yet to be ascertained.
A recent study has investigated the formation of reactive oxygen species, which are key species of atmospheric and physiological chemistry, in aqueous mixtures of secondary organic aerosols (SOA) and mineral dust5.
SOA (fine and ultrafine particulate matter) are created through the oxidation of gaseous volatile organic compounds, which can be emitted from both vegetation and human activities2,3. Mineral dust particles originate from arid and semiarid areas and can transported over thousands of kilometres4. Together, SOA and mineral dust account for a major proportion of atmospheric particulate matter yet the interactions between these two important components and their influences on cloud chemistry and public health are not well understood.
In combination with a spin-trapping technique, liquid chromatography-tandem mass spectrometry (LC-MS/MS) and a kinetic model, electron paramagnetic resonance (EPR) spectrometry using a Bruker EMXplus-10/12 CW-EPR spectrometer revealed that substantial amounts of reactive oxygen species is formed in aqueous mixtures of SOA and various kinds of mineral dust. This is probably due to decomposition of the organic hydroperoxides present in the SOA.
Therefore, by using this EPR technique with Bruker instrumentation, the researchers were able to suggest from their findings that the inhalation of SOA and mineral dust could result in the release of damaging free radicals with the respiratory tract and lungs, which may contribute to oxidative stress and the adverse health effects reported for atmospheric particulate matter.