Ambient fine particulate matter in Latin American cities: Levels, population exposure, and associated urban factors

Abstract

Background Exposure to particulate matter (PM 2.5 ) is a major risk factor for morbidity and mortality. Yet few studies have examined patterns of population exposure and investigated the predictors of PM 2.5 across the rapidly growing cities in lower- and middle-income countries. Objectives Characterize PM 2.5 levels, describe patterns of population exposure, and investigate urban factors as predictors of PM 2.5 levels. Methods We used data from the Salud Urbana en America Latina/Urban Health in Latin America (SALURBAL) study, a multi-country assessment of the determinants of urban health in Latin America, to characterize PM 2.5 levels in 366 cities comprising over 100,000 residents using satellite-derived estimates. Factors related to urban form and transportation were explored. Results We found that about 172 million or 58% of the population studied lived in areas with air pollution levels above the defined WHO-AQG of 10 μg/m 3 annual average. We also found that larger cities, cities with higher GDP, higher motorization rate and higher congestion tended to have higher PM 2.5 . In contrast cities with higher population density had lower levels of PM 2.5 . In addition, at the sub-city level, higher intersection density was associated with higher PM 2.5 and more green space was associated with lower PM 2.5 . When all exposures were examined adjusted for each other, higher city per capita GDP and higher sub-city intersection density remained associated with higher PM 2.5 levels, while higher city population density remained associated with lower levels. The presence of mass transit was also associated with lower PM 2.5 after adjustment. The motorization rate also remained associated with PM 2.5 and its inclusion attenuated the effect of population density. Discussion These results show that PM 2.5 exposures remain a major health risk in Latin American cities and suggest that urban planning and transportation policies could have a major impact on ambient levels.

Scaling of mortality in 742 metropolitan areas of the Americas

“…Various environmental and policy features linked to the prevalence of these risks factors [including factors such as air pollution, access to healthier and processed foods, walkability, and green spaces ( 50 , 51 )] may be strongly linked to city size in the United States and not so strongly linked to city size in Latin America, as has been observed in a comparison of U.S. and Indian and Chinese cities, which show very different scaling patterns for air pollution ( 52 ). However, an analysis of our same sample of 366 Latin American cities has shown that larger cities of Latin America have higher levels of air pollution, as measured by PM2.5 levels ( 53 ). Larger cities of both regions may also have higher health care capacity ( 54 – 58 ), although a recent study in Latin American cities showed that deaths due to conditions for which the health care system should prevent cases are more frequent in larger cities, while deaths due to chronic conditions requiring substantial care are lower in larger cities ( 38 ).…”

Built environment profiles for Latin American urban settings: The SALURBAL study

“…Studies conducted in Latin America, the US and China assessing the relationship between air pollution and urban landscape metrics showed that higher fragmentation, higher population density [ 45 ], edge density [ 71 ] and higher intersection density [ 16 ] were associated with an increase in the number of days exceeding the air quality index for PM2.5. The findings of our study are partially, consistent with these results, but expand on the importance of the interaction among the number of patches, patch size and isolation, and the street design profiles.…”

“…Our study also indicated that profiles with moderate to high street connectivity and moderate street directness ( semi-hyperbolic grid and spiderweb profiles) were associated with high air pollution. Together, moderate directness of streets and high street connectivity could represent proxy indicators for walkability that are also related with lower speed and increased stop and go traffic, which in turn increases the levels of PM2.5 [ 16 ]. These results could be useful for the 12 Latin American cities in the C40 initiative for healthier and sustainable cities which belong to the spiderweb profile characterized by higher street connectivity, shorter streets and moderate directness [ 72 ].…”

“…Congestion is a major challenge for many large Latin American cities [ 15 ]. In addition, 58% of the urban population lives in areas with air pollution levels above the defined WHO-AQG of 10 μg/m3 annual average [ 16 ]. Despite these challenges, Latin America is also known for its innovative and sustainable transport policies [ 17 ], urban development projects [ 18 ], and social programs [ 19 ].…”

“…A study including 919 cities in Latin American showed that compact and well-connected cities exhibit higher levels of productivity measured by density of radiance from the nighttime imagery [ 10 ]. A previous study of SALURBAL (Salud Urbana en América Latina or Urban Health in Latin America) including 366 cities in 11 countries from Latin America using satellite-derived PM measures showed that higher intersection density was associated with higher PM2.5 [ 16 ]. However, no studies have simultaneously and holistically considered how built environment configurations or profiles (that encompass multiple aspects acting together) are related to other city features across the universe of Latin American cities.…”