Opinion

Relevance of Characterizing PAHs on PM in South-Central Chilean Cities

Fabián Guerrero*

Department of Mechanical Engineering, Universidad Técnica Federico Santa María, Chile

Submission: July 13, 2021; Published: July 27, 2021

*Corresponding author: Fabián Guerrero, Department of Mechanical Engineering, Universidad Técnica Federico Santa María, Avenida España 1680, Valparaíso 2390123, Chile

How to cite this article: Fabián Guerrero*. Relevance of Characterizing PAHs on PM in South-Central Chilean Cities. Organic & Medicinal Chem IJ. 2021; 11(1): 555804. DOI: 10.19080/OMCIJ.2021.11.555804

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Keywords: Polycyclic aromatic hydrocarbons; Residential wood combustion; Forest fires; Air quality

Opinion

South-central Chilean cities, such as Rancagua, Talca, Curicó, Linares, Los Angeles, Concepción, Temuco, Osorno, Valdivia, and Coyhaique, primarily stand out as cities with high levels of atmospheric pollution. The residential wood combustion (RWC) is the major contributor to this phenomenon, turning these zones into saturation areas due to high concentrations of particulate matter (PM₁₀, and PM_2.5) [1,2].

RWC generates a variety of pollutants, such as particulate matter (PM₁₀, PM_2.5, and PM1.0), atmospheric organic aerosols, gaseous combustion products, inorganic compounds, and polycyclic aromatic hydrocarbons (PAHs), the latter being chemical compounds of considerable concern to the scientific community given the carcinogenic and mutagenic properties of some of these substances and their derivatives. In fact, due to their carcinogenic activity, 16 PAHs have been listed as priority PAHs by the Environmental Protection Agency (EPA-USA), as shown in Table 1, naphthalene (the lightest of the PAHs) and benzo(a) pyrene being the most toxic and carcinogenic, respectively [3,4].

Most investigations into air quality in Chile are focused on characterizing emissions of particulate matter (PM₁₀ and PM_2.5); nevertheless, it is essential to conduct organic speciation of PM to identify its chemical composition, with particular attention paid to PAHs given their toxicity as carcinogenic and mutagenic compounds. As airborne PAHs can adsorb on PM2.5, the responsibility for particle toxicity may be attributed to these chemical compounds. Most polycyclic aromatic hydrocarbons (70 to 90%) are adsorbed on surfaces of particles with a micrometer-scale diameter (inhalable particles) [5]. These particles can settle in the respiratory system and thus increase the occurrence of adverse health conditions. Since PAHs are semi-volatile compounds, the species with the highest molecular mass predominates in the chemical speciation of PM_2.5, and this mass fraction is highly harmful to humans. Therefore, exposure to PAHs may increase the risk of skin and lung cancer, among other diseases [5].

In Chile, it is estimated that an increase in emissions of PAHs in the particulate phase will be produced because of increasing residential wood combustion in south-central cities of the country due to confinement brought by the current sanitary emergency (COVID19 pandemic). As the population is required to stay indoors for a significant fraction of the day, it is expected that the hours of operation of household stoves will increase, and, thus, an increase in PM emissions to the atmosphere is also projected. Moreover, another interesting source of PAH emissions that must be considered is the occurrence of forest fires, where this contribution may be intensified as a result of the recent recorded increase in the number of these events and burnt area, partially explained by climatic factors, such as the increase regarding extreme temperatures and the occurrence of heat waves combined with the reduction in the level of precipitations, which leads to drought conditions, enhancing a predisposition of vegetation to inflammation [6].

In this scenario, it is urgent to study PAHs in greater depth in densely polluted Chilean cities, such as Coyhaique, which has the highest concentrations of fine PM (annual average of 66 μg m-3) in the Americas [7]. Furthermore, this characterization should address the concentration of these substances as well as their spatial distribution, spatial variation, source distribution, and risk management for human health. This information would provide a scientific basis for the establishment or improvement of standards to further restrict the emissions of these pollutants to reduce impacts on human health.

References

1. Guerrero F, Yáñez K, Vidal V, Cereceda Balic F (2019) Effects of wood moisture on emission factors for PM2.5, particle numbers and particulate-phase PAHs from Eucalyptus globulus combustion using a controlled combustion chamber for emissions. Sci. Total Environ 648: 737-744.
2. Cereceda Balic F, Toledo M, Vidal V, Guerrero F, Diaz Robles L A, et al. Emission factors for PM₅, CO, CO₂, NOx, SO₂ and particle size distributions from the combustion of wood species using a new controlled combustion chamber 3CE. Sci Total Environ 584-585: 901-910.
3. Ravindra K, Sokhi R, Van Grieken R (2008) Atmospheric polycyclic aromatic hydrocarbons: Source attribution, emission factors and regulation. Atmos Environ 42: 2895-2921.
4. Yan D, Wu S, Zhou S, Tong G, Li F, et al. (2019) Characteristics, sources, and health risk assessment of airborne particulate PAHs in Chinese cities: A review. Environ Pollut 248: 804-814.
5. Kim K H, Jahan S A, Kabir E, Brown R J C (2013) A review of airborne polycyclic aromatic hydrocarbons (PAHs) and their human health effects. Environ Int 60: 71-80.
6. Guerrero F, Hernández C, Toledo M, Espinoza L, Carrasco Y, et al. (2021) Leaf Thermal and Chemical Properties as Natural Drivers of Plant Flammability of Native and Exotic Tree Species of the Valparaíso Region, Chile. Int J Environ Res Public Health 18: 7191.
7. Perez P, Menares C, Ramírez C (2020) PM2.5 forecasting in Coyhaique, the most polluted city in the Americas. Urban Clim 32: 100608.