Pathogenic Mechanisms of Secondary Organic Aerosols

Abstract

Air pollution represents a major health problem and an economic burden. In recent years, advances in air pollution research has allowed particle fractionation and identification of secondary organic aerosol (SOA). SOA is formed from either biogenic or anthropogenic emissions, through a mass transfer from the gaseous mass to the particulate phase in the atmosphere. They can have deleterious impact on health and the mortality of individuals with chronic inflammatory diseases. The pleiotropic effects of SOA could involve different and interconnected pathogenic mechanisms ranging from oxidative stress, inflammation, and immune system dysfunction. The purpose of this review is to present recent findings about SOA pathogenic roles and potential underlying mechanisms focusing on the lungs; the latter being the primary exposed organ to atmospheric pollutants.

Chronic Exposure to Secondary Organic Aerosols Causes Lung Tissue Damage

“…Herein, we show that exposure to SOA resulted in lung inflammation and tissue destruction, confirming some of our previously proposed hypotheses. 45 Unlike earlier studies reporting that short exposure to SOA does not lead to lung inflammation and injury, 46,47 we found that it is chronic exposure to this pollutant that resulted in lung tissue injury. We then went on to document this finding.…”

Weight loss and abnormal lung inflammation in mice chronically exposed to secondary organic aerosols

“…8,[12][13][14] In this regard, a series of studies mainly cell culture studies revealed a role for SOAs in cell oxidative stress, toxicity and inammation. 12,15 While data from these cell culture systems studies are very informative, they do not translate the complex inammatory response of human diseased situations especially following a long-term exposure to SOAs. Also, the scant in vivo studies that were carried out over a short period of time (few days) of exposure to SOAs were inconclusive in that a minor or no inammatory response was observed.…”

“…8,12–14 In this regard, a series of studies mainly cell culture studies revealed a role for SOAs in cell oxidative stress, toxicity and inflammation. 12,15…”

Toxicological Effects of Secondary Air Pollutants

“…However, public concern about the atmospheric environment was triggered by numerous cases of secondary pollutants outbreaks, such as Los Angeles photochemical smog, etc., and the formation of more toxic secondary pollutants, such as ozone, peroxyacetyl nitrate(PAN), and secondary particulate matter [12] . The new WHO(World Health Organization) air quality guidelines also highlight the health risk of secondary pollutants, such as ozone, and dramatically raise the standard of NO2, which is vital in secondary pollutants formation [13] , but the health risks of secondary pollutants are highly uncertain [14,15] . First of all, this is mainly due to the fact that the formation of secondary pollutants involves a variety of physical and chemical processes and thousands of compounds at the same time.…”

“…Numerous research studies have pointed out that air pollution is related to chronic obstructive pulmonary disease (COPD) and other respiratory diseases [7,[28][29][30] . Inflammation is a pivotal physiological mechanism in dealing with the invasion of external harmful substances [14,31] . Along with primary pollutants, such as heavy metals, secondary pollutants can directly or indirectly impact the vital molecules, such as affecting the structure and function of receptors [31,32] , mRNA [33,34] , thereby causing or aggravating non-infectious inflammatory responses.…”