Clean air is critical for life.� Every person on the planet breathes, on average, 12,870 liters of air each day.� Even small amounts of pollution can make that air unhealthy to breathe.� Those most vulnerable to air pollution include babies and children, who are particularly susceptible because their respiratory systems are not yet fully developed.� Other sensitive groups include the elderly and people who suffer from heart and respiratory disease.� Air pollution can affect people directly � through breathing unhealthy air � and indirectly � by damaging the environment in which they live.� Polluted air can have a series of direct and indirect effects on the environment, including impacts on vegetation and man-made materials, acidification and eutrophication of ecosystems, degradation of visibility, and important effects on climate.�
In Asia and the western Pacific regions alone, air pollution is estimated to be responsible for a million advanced deaths each year.� The World Health Organization (WHO) estimates that one billion people across the globe are exposed to outdoor air pollution that exceeds recommended health-based air quality levels.� Worldwide, air pollution causes tens of millions of respiratory and other illnesses, severely affecting quality of life, and reducing economic activity.� Although air pollution has a significant impact on all people exposed, the poor are particularly at risk, having fewer opportunities to avoid exposure to damaging pollutants.� In this way, air pollution contributes significantly to the downward cycle of poverty around the world.�
Pollutants such as particulate matter (PM) and ozone contribute to rising �background levels� (general level of air quality before adding pollution from local sources) and �atmospheric brown clouds� (haze comprised of many pollutants that can be transported far beyond their source region) in various parts of the globe.� They also contribute to what has been called the �greying� of the northern hemisphere.� They not only increase health damage to crowded urban populations, but damage the ecosystems which help underpin sustainable development.� In rural areas, significant crop damage from the pollutant ozone has been observed in Asia and throughout various parts of the world. Acidification of ecosystems from long-range transboundary air pollution remains a threat in areas with significant emissions from the burning of fossil fuels, particularly in East Asia.�
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<span>The new student is overgeneralizing the situation by concluding that because in the first class</span><span> the people sitting in the back row answer most of the questions this means that the smartest students sit in the back.
The situation was only a coincidence, and the new student made fact of it.
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