Sunday, January 26, 2014

Linking Air Pollution and Heart Diseases in Santiago

Around one third of Chile’s population lives in an urban conglomeration which sits in a natural bowl, traps pollution and — according to a recent study —leads to a range of health problems including cardiovascular disease. Santiaguinos aren’t the only ones to face these health complications — nearly 90 percent of Chileans live in towns and cities. But the level of pollution in the capital, driven mainly by urban traffic, is nothing short of alarming.

Link to the article on Santiago Times.

Real Time Air Quality in Santiago and Other Chilean Cities.

A report published this month in Science of the Total Environment found that, over the study period of 3 years, some of the airborne pollution markers exceeded European safety levels three in every four days. A major contributor to the problem is geographical and atmospheric conditions. The city lies in a valley between two mountain ranges — the Andes and the Cordillera de la Costa— which traps pollutants by minimizing air circulation.

In summer months, clear skies and high temperatures only exacerbate the situation through a variety of chemical processes. For example, toxic ozone is more likely to form with high temperatures via the oxidation of carbon monoxide (CO) in the presence of nitrogen oxides. Some of the main chemical culprits in pollution include sulphur dioxide (SO2), nitrogen dioxide (NO2), ozone (O3), CO and particulate matter. High levels of these compounds are thought to be related to ill health — in particular cardiovascular problems — and the exacerbation of pre-existing medical conditions.
The study set out find evidence for this relationship.

High pollution levels, more hospital admissions

The authors acquired data on particulate matter, CO, NO2 and O3 levels from 2004 to 2007 in seven of eight weather monitoring stations dotted around Santiago —Cerrillos, El Bosque, La Florida, La Paz, Parque O’Higgins, Providencia and Pudahuel. They compared this with Health Ministry figures on the number of hospital admissions for heart problems registered by both public and private health providers. But rather than simply testing whether there was a simple association between air pollution and hospital admissions for heart problems, the researchers applied a lagged analysis to the data. This allowed them to determine the impact that varying levels of pollution on particular days had on hospital admission — both the immediate effects and those felt over subsequent days.

Evidence backs calls for tighter controls

The report found evidence of the negative impact of pollution on physical health for the people of Santiago. During the study period levels of some, but not all, pollutants were considerably higher than both Chilean National Ambient Air Quality Standard (NAAQS) and World Health Organisation standards. Also, though average levels of some pollutants were low, a large amount of daily variation meant that they become very high at certain times of day. As levels of pollutants such as NO2, CO and particulate matter increased, so too did hospital admissions for cardiovascular disease. A notable exception was ozone.

The effects were strongest either immediately or with a lag of 1-2 days, whereafter the effects tended to lessen. The authors calculate that the risk due to the exposure to airborne pollution increased hospital admissions for cardiovascular disease amounted to approximately 5 percent. Interestingly, a similar link between long-term pollution (particulate matter) and heart disease was reported in Europe this month in the British Medical Journal. This combined evidence suggests that Chile needs to enforce tighter controls on air pollution to combat the exacerbation of cardiovascular disease — particularly in Santiago where environmental conditions and heavy urbanization make the potential impact of air pollution even more devastating to individuals.

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