**Abstract**

This chapter provides an introduction to particulate matter by discussing various ways of categorisation, characterisation and their health effects. The natural and anthropogenic sources of atmospheric particulate matter are discussed. The chapter also introduces qualitatively some aerosol concepts, such as their chemical composition and size distribution. Some examples are provided to illustrate how particulate matter, despite being microscopic particles, can manifest themselves in the atmosphere. Finally, the various pathways by which particulate matter impacts the health system are reviewed along with their interactions to understand concept behind the PM-associated health effects.

**Keywords:** Aerosol, PM, Health effects, Chemical constituents, Heavy metals

## **1. Introduction**

Air pollution has become a major environmental and health concern worldwide. Even though, the effect of air pollution has been recognised since classical times yet the studies correlating human health and air pollution came into existence in near twentieth century. According to WHO, air pollution refers to contamination/or changes in the natural environment by physical, chemical or biological agent (pollutants), which may be contributed by natural or anthropogenic sources. In reality, some of these pollutants are naturally present but are of least concern because of their lower levels. Once, their level cross prescribed levels they are harmful for humans including other living organisms and natural environment. National Ambient Air Quality Standards (NAAQS), sets limits for six criteria air pollutants viz. carbon monoxide (CO), lead (Pb), nitrogen dioxide (NO2), ozone (O3), particulate matter (PM) and sulphur dioxide (SO2).

Particulate matter refers to a complex mixture of solid particles and liquid droplets (EPA). In general, they may vary in size and composition depending upon its location and time of its source e.g., PM emitted from mining activities will have metal contaminants associated with them whereas sea aerosols will mainly contain organic contaminants. Depending on these it might contain nitrates, sulphates, elemental and organic carbon, organic compounds (PAH), biological compounds (endotoxin, cell fragments) and heavy metals (Fe, Ca, Ni, Zn etc.). PM are becoming increasingly ubiquitous but the disease burden related to PM pollution is quite high in low- or middle-income nations as compared to developed countries. According to WHO every nine out of ten people breathe polluted air worldwide. The State of Global Air Report in 2020 reported that more than 90% of the world's population were exposed to PM2.5 level that exceeds WHO guideline limits, with

#### **Figure 1.**

*Dust event at Safdarjung Tomb Delhi, India (Image Courtesy: Shubham).*

developing countries more at risk. Also, studies on particulate matter exposure have explained the various health associated problems including heart attacks, asthma, decreased lung capacity, respiratory symptoms such as irritation of airways, difficulty in breathing and premature death (**Figure 1**) [1–4].

The size of PM can be related to their sources, due to the physical processes that form these particles and the atmospheric processes that control the fate and evolution of particle size distributions in the ambient atmosphere. PM10 (particles with aerodynamic diameters less than or equal to 10 μm) is generated largely by physical processes, including resuspension of soil and road dust, sea spray, agricultural tilling, vehicular abrasion (i.e. tyre and brake wear), and fugitive dust emission from industrial sources (**Figure 1**). PM2.5 (particles with aerodynamic diameters less than or equal to 2.5 μm) comprise predominantly the condensation of secondary inorganic and organic compounds and PM0.1 (particles with aerodynamic diameters less than or equal to 0.1 μm) particles comprise predominantly secondary sulphate and bisulphate ion, secondary nitrate ion, secondary ammonium ion, and carbonaceous PM from primary and secondary sources, but also include some crustal materials. The origin of PM0.1 is attributed to combustion sources and atmospheric nucleation. They have short atmospheric lifespan as they grow to form accumulation particles. They get enriched in carbonaceous aerosols and metals from combustion of oil and other fuel, also from high temperature processing of metals. However, smaller particles can affect and damage the body organs to the greater extent; although the impact is variable depending upon the concentration and composition of particulate matter. For example, heavy metals like lead, arsenic and cadmium are well known to cause toxicity in the human body, whereas sulphur aerosols which form sulphuric acid are corrosive and can damage the tissues; PAHs are potent carcinogens and can cause cancer (**Table 1**).

#### **1.1 Air quality standards**

Air pollution levels in most of the urban areas have been a matter of concern. To improve air quality, WHO is working with different countries to understand the problem related with air pollution. It has revised guidelines for key air pollutants in the ambient environment: particulate matter, nitrogen dioxide, sulphur dioxide, *Particulate Matter and Human Health DOI: http://dx.doi.org/10.5772/intechopen.100550*


**Table 1.**

*Particulate matter (PM); size attribution and penetration to human respiratory system [5–7].*


**Table 2.** *Air quality standards.*

carbon monoxide and ozone. The concentration limits for these air pollutants along with prescribed European Union Ambient Air Quality Standards are given in **Table 2**.
