Origin, Structural Characteristics, and Health Effects of Atmospheric Soot Particles: A Review

Abstract

Purpose of Review

This review summarizes the current knowledge (definition, source, formation, structure, chemical composition, and health effects) about atmospheric soot particles and aims to analyze their health effects combined with their structural characteristics.

Recent Findings

The new understanding of soot microstructure (analogous to reduced graphene oxide (RGO)) suggests the presence of oxygen-containing functional groups (OFGs) in carbonaceous core (CC) of soot, which may enhance its health effects. Toxicological studies have proved that the two major components (CC and outer coating) both contribute to soot toxicity, but there is still controversy over who is playing the main role. Recently, there are many studies questioning the past experimental results. The bioavailability of the outer coating bound on CC is particularly pointed out to be taken into account for soot toxicity. Existing epidemiological studies on black carbon (BC), a near-synonym of soot in atmospheric science, have prompted the adverse health effects especially for cardiovascular system. A stronger association between short term BC exposure and health endpoints is lately found than fine particulate matter (PM_2.5), but still needs more consistent evidence. Therefore, the health effects of soot need more attention as well as comprehensive and in-depth research.

Summary

It is evident from the review that soot is a responsible agent for adverse health effects, which may exceed PM_2.5. The CC and outer coating have been proved to exert toxicity separately, of which oxidative stress, inflammation, and DNA damage are most important toxicity mechanisms. However, their antagonistic interaction may weaken the toxicity of the whole soot particle.