Heavy Metals Content and Health Risk Assessment in Airborne Particulate from the Calabria Region, Southern Italy

Airborne particulate matter (PM) consists of a broad class of chemically and physically different elements, varying in sizes, chemical compositions, formations, sources, and concentrations [1,2]. Exposure to PM has a negative impact on human health, and it contributes significantly to increases in premature deaths due to cardiovascular and respiratory diseases [3,4]. PM contains sulfates, nitrates, ammonium ions, hydrogen ions, other inorganic ions (e.g., Na⁺, K⁺, Ca²⁺, Mg²⁺, and Cl⁻), particle bound water, heavy metals, elemental carbon, and organic compounds [5,6]. The major urban causes of these PM-associated compounds are related to anthropogenic activities, such as mining, construction, industrial emissions, road traffic (motor vehicles, railways), various combustion processes, power plants, and domestic heating [7,8]. In particular, airborne particles with diameters lower than 10 µm (PM10) can affect climate and reduce visibility, as they participate in many significant atmospheric processes [9,10]. They are often harmful for health because, being able to overcome the protective barriers present in the first portion of the respiratory system, they can reach deeper areas [11]. The effects of PM10 are proportional to its concentrations, and there are no threshold values below which there is no danger to health. This is mainly due to the presence of carcinogenic compounds embedded in the particulate matter itself, such as heavy metals [12] (i.e., naturally occurring elements with relatively high density, atomic number, and atomic weight [13,14,15]). Their multiple uses in industry, housing, agriculture, medicine, and technology raise concerns about their possible impact on human health and the environment [16,17,18]. Heavy metals such as Cd, Ni, and Pb, also present at very low concentrations and have adverse effects on the human body, causing acute and chronic toxicity [19]. Therefore, for the protection of the environment and to ensure sufficiently clean air levels, heavy metals must be kept at safe levels [20]. In the last decades, a number of studies have been carried out in order to assess the levels of heavy metals in PM10 and their potential risks [21,22,23,24,25,26,27,28].