Rural to urban migration is a global phenomenon, but nowhere in the world is this transition occurring more rapidly than in developing countries. One of the unique challenges arising from more densely packed city environments is the rise in air pollution. Naturally, particulate matter in the ambient air grows along with increased vehicle use, demand for energy production, and household energy consumption. In developing nations, increasing pressure is placed on these sources of pollution as incomes rise. Exposure to air pollution, especially over the long term, can have negative health effects. Evidence regarding the impact of measures to mitigate harmful air pollution in the short run is limited.
Chile experienced rapid economic development and urban migration in the second half of the 20th century.[3, 4] Its capital, Santiago, experienced population growth and subsequent rise in air pollution; in the 1980s and 1990s particulate matter in the air would frequently be greater than six times the levels recommended by the World Health Organization. Growing public discontent with air quality prompted the government to implement a series of policies to address the issue, culminating in the 1997 ‘Plan de Prevención y Descontaminación Atmosférica’ (PPDA). In addition to other policies, the PPDA implemented the public announcement of “Environmental Episodes” on days when particulate matter levels were expected to exceed certain thresholds. During these episodes the government also mandated other protocols, including restricted driving and the temporary shutdown of particular emission sources. This study focuses on the effect of these short term policies to curb emissions and lower particulate matter over small time periods. Researchers also utilized health system morbidity data to examine impacts on elderly (age 65 and up) health.
Researchers utilized daily air quality and weather measures taken in Santiago by the Chilean Ministry of the Environment from 1989 to 2008.
Examining air quality and weather indicators in the five days leading up to an episode, researchers calculated the probability that a given day would coincide with an episode announcement, based on the characteristics of its lead-up days. Shifting their focus to the pre-PPDA days before 1997, researchers then ‘matched’ pre-1997 days to post-1997 ‘episode’ days on the basis of these lead-up day characteristics. Essentially, researchers identified sequences of days with similarity on weather and pollution features; the matched days differed only on whether they occurred in the pre- or post-PPDA period (i.e. before or after episode announcements became standard practice).
By comparing how air quality and mortality indicators changed in the days following these post-1997 ‘episodes’ versus similar days in prior years, researchers were in a position to assess the impact of short run PPDA policies.
Results and Policy Implications
Researchers found that the designation of environmental episodes through the PPDA did improve air quality. An episode announcement and associated protocols reduced particulate matter by 17 percent of expected levels in the absence of such protocols. The results further demonstrated that announcements were associated with a decline in elderly deaths (about 15 fewer in the three days following), although this relationship is only marginally statistically significant.
These findings suggest that public policies aimed at curbing air pollution in the short run can be successful at improving air quality and health, although more research is needed to parse out the effects of specific interventions. As urbanization continues in the developing world, managing air pollution is increasingly important. This research suggests that short term air pollution policies may be an effective part of those solutions.
 “World Urbanization Prospects, the 2011 Revision”, 2012. United Nations Department of Economic and Social Affairs: Population Division. Retrieved from http://esa.un.org/unpd/wup/Analytical-Figures/Fig_1.htm
 Graff Zivin, Joshua, and Mathew Neidell. "Environment, Health, and Human Capital." Journal of Economic Literature 51 (2013): 689-730.
 Saravia, A. 2008. “The Chilean Agricultural Transformation During the Second Half of the Twentieth Century: A Story of Institutional Change.” Institute for Advanced Developmental Studies (WP 8). Retrieved from http://www.academia.edu/4078157/Saravia_2008_The_Chilean_agricultural_transformation_during_the_second_half_of_the_twentieth_century-_A_story_of_institutional_change
 “OECD Urban Policy Reviews, Chile 2013.” 2013. Retrieved from http://www.oecd-ilibrary.org/urban-rural-and-regional-development/oecd-urban-policy-reviews-chile-2013_9789264191808-en
 World Health Organization, 2011. Air Quality and Health.
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