For decades, morbidity and mortality associated with respiratory illness have been on a steady rise. This upward trend of respiratory illness can be attributed largely to the rise in global air pollution stemming from an uptick in anthropogenic factors associated with global economic growth and industrialization, namely energy consumption and vehicular exhaust emissions.  These anthropogenic activities result in dangerous atmospheric modifications with the introduction of gaseous and particulate substances into the air we breathe.  Today, a whopping 91% of the global population is forced to breathe air that fails to meet air quality standards set by the World Health Organization.  The most common air pollutants (ozone, sulfur dioxide, nitrogen dioxide, carbon monoxide, lead, hydrocarbons, and particulate matter) wreak havoc on human respiratory health in both the short-term and the long-term.  The effects on lung function by air pollutants depend on: type of pollutant, environmental concentration of the pollutant, duration of exposure, ventilation of exposed individuals, and extent of interaction of pollutants with aeroallergens.  Some respiratory illnesses commonly associated with air pollution include: chronic obstructive pulmonary disease (COPD), acute lower respiratory infections, emphysema, and asthma. Air pollution is not only associated with an increase in the incidence and prevalence of these disorders, but also with an increase in the severity of the manifestation of these disorders. 
Since traffic concentrates heavily in and around cities, and there is a greater need for energy consumption in cities than in rural areas, a vast proportion of global air pollution stems from urban centers. So, urban residents bear the brunt of ill health associated with pollution. Such was exemplified by Tania Sih; when comparing respiratory health outcomes of children in urban São Paolo (high pollution) and rural (minimal pollution) areas in Brazil, urban children exhibited rhinitis at 7% compared to 4% in rural children and sinusitis at 12% compared to 8% in rural children.  Sih also found that the children in São Paolo presented more absenteeism from school, required more antibiotic or antiallergic treatments, had more hospitalizations for respiratory complications, and required more ear, nose, and throat surgeries than rural children.  So, the adverse effects of air pollution can present not only immediately in health, but can also impair higher educational attainment, work opportunities, and productivity years into adulthood by virtue of school absenteeism in childhood.
All demographic groups are not affected equally by respiratory illness within urban centers. Children and the elderly more frequently visit emergency rooms for respiratory issues associated with air pollution than do other age groups.  Further, as a result of unjust housing practices and wealth inequality, low-income BIPOC communities tend to live in more polluted neighborhoods and closer to busy roadways than do their white counterparts in the United States.  This inequity in respiratory health outcomes between racial and ethnic groups is environmental injustice and racism. In order to combat this environmental injustice and to reduce air pollution, altogether, it will be necessary to impose more stringent testing regulations for new cars, as vehicular emissions are the largest contributor to air pollution. In addition to that, our cities must be made more accessible for walking, biking, and public transportation. For widespread adoption of these alternative transportation methods, the healthy choice must become the easy choice for urban residents.
On a global note, it is crucial to keep in mind that pollution is outsourced to developing countries by wealthy, developed nations. So, although countries like India and China lead the world in amount of air pollution, criticizing these countries for such is neither reasonable nor conducive to change. Rather, such underprivileged nations must be aided in funds and resources by the wealthy world and intergovernmental organizations because air pollution knows no national borders.