An Introduction to Environmental Epidemiology: the Case of Air Pollution

This article has been written by the researcher David Rojas and the science communicator Raül Torán, both from ISGlobal, and it has been published at Fundació Catalunya La Pedrera in Catalan

What is environmental epidemiology? Why is it so important? Can we bring research into the classroom? The ultimate goal of all of the research done at ISGlobal is to improve health and promote health equity through excellence in research and the translation and application of the knowledge generated. Our objective is to tackle the health challenges facing a globalized world.

Environmental epidemiology focuses on the ways environmental factors affect the health of populations

How can we find out whether mercury is toxic to our health? Or whether pollution from cars can increase the risk of heart attack? These are the kinds of questions we can answer through laboratory research—known as toxicology—and through the study of human populations, in other words, epidemiology. Epidemiologists study the factors that cause disease and the distribution of diseases within the population. Environmental epidemiology focuses on the ways environmental factors (physical, chemical and biological) affect the health of populations.

Examples of Epidemiological Studies

For example, an epidemiologic study could analyse how the percentage of overweight people in the population has recently increased in developed countries and study the links between this trend and its possible causes (lack of physical exercise, diets low in fruit and vegetables or high in junk food or food with a high content of sugar and fats, and so on). We could also analyse the distribution of lung cancer in Spain, trying to identify why there are more cases in some areas and fewer in others and to relate those findings to environmental or lifestyle factors (higher incidence of smoking or a typical diet characterised by a high red meat content, for example).

For example, an epidemiologic study could analyse how the percentage of overweight people in the population has recently increased in developed countries

Our health is affected by many aspects of our lives: personal factors (age and sex as well as hereditary and socioeconomic factors); lifestyle (diet, physical activity, work-life balance); the local community and economy (income levels, investment); what we do (our jobs, how we travel, where we live); our built environment (public spaces, road network); and the natural environment around us (green spaces nearby).

Air Pollution and Health

Air pollution has many short- and long-term effects on human health. Urban air pollution, generated mainly by road traffic, increases the risk of chronic respiratory diseases such as lung cancer and the risk of acute conditions such as pneumonia and cardiovascular events. Air quality affects us all, whether we are sick or healthy, young or old.

Air quality affects us all, whether we are sick or healthy, young or old

In a recent study, ISGlobal researchers observed decreased improvement in cognitive development among primary school children exposed to higher levels of air pollution because of the proximity of their school to busy roads. The regions of the brain linked to executive functions such as working memory and attention—essentially the prefrontal cortex and striatum—have shown inflammatory responses after exposure to traffic-related air pollution.

In another study, ISGlobal researchers discovered that maternal exposure in early pregnancy to nitrogen dioxide (NO2), a pollutant that comes mainly from road traffic, was associated with reduced foetal growth. The outcomes were based on ultrasound measurements of growth during pregnancy and measures of size at birth.

NO2 pollution in the city of Barcelona. The white dots are schools less affected by air pollution and the black dots are schools with higher exposure. Source: ISGlobal.

In a recent collaboration with a German-led study, researchers who studied two cohorts of German adolescents found that exposure to air pollutants was associated with higher hyperactivity and inattention scores.