Air Pollution and Noncommunicable Diseases: A Review by the Forum of International Respiratory Societies' Environmental Committee, Part 1: The Damaging Effects of Air Pollution

Abstract

Air pollution poses a great environmental risk to health. Outdoor fine particulate matter (particulate matter with an aerodynamic diameter < 2.5 μm) exposure is the fifth leading risk factor for death in the world, accounting for 4.2 million deaths and > 103 million disability-adjusted life years lost according to the Global Burden of Disease Report. The World Health Organization attributes 3.8 million additional deaths to indoor air pollution. Air pollution can harm acutely, usually manifested by respiratory or cardiac symptoms, as well as chronically, potentially affecting every organ in the body. It can cause, complicate, or exacerbate many adverse health conditions. Tissue damage may result directly from pollutant toxicity because fine and ultrafine particles can gain access to organs, or indirectly through systemic inflammatory processes. Susceptibility is partly under genetic and epigenetic regulation. Although air pollution affects people of all regions, ages, and social groups, it is likely to cause greater illness in those with heavy exposure and greater susceptibility. Persons are more vulnerable to air pollution if they have other illnesses or less social support. Harmful effects occur on a continuum of dosage and even at levels below air quality standards previously considered to be safe.

Keywords: air pollution; mechanism of damage; noncommunicable diseases.

Figure 1

Anthracotic lung. Inhaled particulates are usually cleared through the respiratory mucociliary apparatus and scavenged by alveolar macrophages. Particles can move into the interlobular septal lymphatics and be cleared by the lymphatic system, but if these mechanisms are overwhelmed, particulates may clog lymphatics and be deposited in the lung interstitium. Ultrafine particles gain entrance to mobile cells and can be transported to all parts of the body. Although this anthracotic lung is characteristic of smokers and workers in dusty occupations, anthracotic deposits are often found in urban dwellers from air pollution.

Figure 2

Pollution damage by systemic inflammation. This scanning electron micrograph of the terminal and respiratory bronchioles are the sites where most material accumulates, making it the area of the lung most vulnerable to pollution. In addition, this figure depicts four ways that pollution can affect all organs through systemic inflammation. Ultrafine particles pass through the alveolar-capillary membrane, are endocytosed, and distributed throughout the body. They induce similar inflammatory reactions in other organs. (Copyright reserved Dean Schraufnagel.)