AIR POLLUTION AND URBANIZATION

The World Health Organization defines air pollution as contamination of the indoor or outdoor envi-ronment by any chemical, physical, or biological agent that modifies the natural characteristics of the atmosphere. Common sources of air pollution include household combustion devices, motor vehicles, industrial facilities, and forest fires. Urbanization, driven by rapid demographic and industrial growth, has significantly increased the global burden of air pollution. The major pollutants include particulate matter, carbon monoxide, ozone, nitrogen dioxide, sulfur dioxide, and volatile organic compounds. These pollutants not only affect ambient air quality but also exert harmful effects on human health through well characterized biological mechanisms. A key target of air pollutants is the epithelial barrier system of the respiratory tract, skin, and gastrointestinal mucosa interfaces that form the body’s first line of defense against the external environment. Pollutant-induced oxidative stress leads to disruption of the epithelial barrier, lipid and protein oxidation, immune activation, and epigenetic modifications, resulting in sustained inflammation and increased susceptibility to allergens and pathogens. These processes interact with genetic and environmental factors, contributing to immune dysregulation and the development of chronic diseases. Epidemiological evidence consistently shows that exposure to major pollutants, particularly traffic related air pollutants, is associated with increased incidence, prev-alence, and severity of asthma, allergic rhinitis, and atopic dermatitis. Early life exposure including the prenatal period appears to be a critical determinant of disease onset. Children, socioeconomically disadvantaged groups, the elderly, and individuals with underlying cardiovascular diseases are particu-larly vulnerable to these adverse effects. Reducing air pollution requires integrated strategies targeting transportation emissions, industrial sources, and urban planning. Low Emission Zones, stricter emis-sion standards, and expanded green infrastructure measures have shown significant health benefits. Addressing air pollution through evidence-based environmental policies and preventive health mea-sures is of great importance for protecting vulnerable populations and reducing the global burden of allergic diseases.Keywords: Air pollutants; Air pollution; Allergic rhinitis; Asthma; Atopic dermatitis; Particulate matter; Urbanization