Airborne Particulate Matter and Human Health: Toxicological Assessment and Importance of Size and Composition of Particles for Oxidative Damage and Carcinogenic Mechanisms

Abstract

Air pollution has been considered a hazard to human health. In the past decades, many studies highlighted the role of ambient airborne particulate matter (PM) as an important environmental pollutant for many different cardiopulmonary diseases and lung cancer. Numerous epidemiological studies in the past 30 years found a strong exposure-response relationship between PM for short-term effects (premature mortality, hospital admissions) and long-term or cumulative health effects (morbidity, lung cancer, cardiovascular and cardiopulmonary diseases, etc). Current research on airborne particle-induced health effects investigates the critical characteristics of particulate matter that determine their biological effects. Several independent groups of investigators have shown that the size of the airborne particles and their surface area determine the potential to elicit inflammatory injury, oxidative damage, and other biological effects. These effects are stronger for fine and ultrafine particles because they can penetrate deeper into the airways of the respiratory tract and can reach the alveoli in which 50% are retained in the lung parenchyma. Composition of the PM varies greatly and depends on many factors. The major components of PM are transition metals, ions (sulfate, nitrate), organic compound, quinoid stable radicals of carbonaceous material, minerals, reactive gases, and materials of biologic origin. Results from toxicological research have shown that PM have several mechanisms of adverse cellular effects, such as cytotoxicity through oxidative stress mechanisms, oxygen-free radical-generating activity, DNA oxidative damage, mutagenicity, and stimulation of proinflammatory factors. In this review, the results of the most recent epidemiological and toxicological studies are summarized. In general, the evaluation of most of these studies shows that the smaller the size of PM the higher the toxicity through mechanisms of oxidative stress and inflammation. Some studies showed that the extractable organic compounds (a variety of chemicals with mutagenic and cytotoxic properties) contribute to various mechanisms of cytotoxicity; in addition, the water-soluble faction (mainly transition metals with redox potential) play an important role in the initiation of oxidative DNA damage and membrane lipid peroxidation. Associations between chemical compositions and particle toxicity tend to be stronger for the fine and ultrafine PM size fractions. Vehicular exhaust particles are found to be most responsible for small-sized airborne PM air pollution in urban areas. With these aspects in mind, future research should aim at establishing a cleared picture of the cytotoxic and carcinogenic mechanisms of PM in the lungs, as well as mechanisms of formation during internal engine combustion processes and other sources of airborne fine particles of air pollution.

Outdoor Particulate Matter Exposure and Lung Cancer: A Systematic Review and Meta-Analysis

“…Further, smaller particles penetrate more deeply into the lung and are more likely to be retained (Stuart 1976). On the other hand, the coarse fraction of the PM 10 -size group consists mainly of minerals and biologic materials (Valavanidis et al 2008). Thus, PM 2.5 is generally believed to be most relevant to health effects, including cancer.…”

“…Of course, PM 10 includes the PM 2.5 size fraction; however, these particle size groups are believed to differ in regard to human health effects. PM 2.5 includes a higher proportion of mutagenic species (Buschini et al 2001;Valavanidis et al 2008), many of which are products of combustion (Brauer et al 2001). Further, smaller particles penetrate more deeply into the lung and are more likely to be retained (Stuart 1976).…”

Health risk posed by enriched heavy metals (As, Cd, and Cr) in airborne particles from Witwatersrand gold tailings

“…Numerous public statements and claims have been made by individuals and organizations about the dust fallout from tailings affecting public health through several routes of exposure (Bega, 2011a(Bega, , 2011b; Federation for a Sustainable Environment, 2010). Inhalation or ingestion of particulate matter (PM) has been shown to have adverse impacts on human health (Valavanidis, Fiotakis, and Vlachogianni, 2008;Wilson and Suh, 1997). Furthermore, several studies have confirmed a strong link between the inhalation of fine aerosols in ambient environments and the occurrence of cardiopulmonary mortality and respiratory diseases (Berico, Luciani, and Formignani, 1997;Dockery, 2001;Harrison and Yin, 2000;Fubini and Fenoglio, 2007;Griffin, Kellogg, and Shinn, 2001;Park et al, 2004;Pope and Dockery, 2006;Schwartz, 1994;Wilson and Suh, 1997).…”

On-Roadway In-Cabin Exposure to Particulate Matter: Measurement Results Using Both Continuous and Time-Integrated Sampling Approaches

“…Toxicological evidence suggests these associations are related to both the size and composition of traffic-related particulate matter (PM) (Brook 2008;Valavanidis et al 2008;Møller et al 2010). The number distribution of fresh vehicle emissions is dominated by particles in the ultrafine size range (<100 nm) (Kittelson 1998;Robert et al 2007a,b), which have the highest deposition rates in the alveolar region of the lung (Heyder et al 1986), and insoluble ultrafine particles are removed at a very slow rate (Stahlhofen et al 1995;Möller et al 2008).…”