By Wendy Anson
Applying a high-resolution computer model of worldwide air pollutant concentrations, Jason West, Ph.D., and his colleagues at the Department of Environmental Sciences and Engineering, University of North Carolina (UNC) at Chapel Hill, were able to reveal that the most important drivers of emissions affecting world health are significantly different in different regions of the globe.
To study these emissions and their impacts on ozone and particulate matter (PM), West’s group’s analysis used a “chemical transport model” (CTM), which simulates atmospheric chemistry. The group organized the source of anthropogenic emissions into five sectors: energy, residential and commercial, industry, land transportation, and shipping and aviation. With the CTM, the researchers were able to attribute air pollutant concentrations to each of those specific sectors.
The NIEHS-funded team found that residential emissions are dominant in India and Africa; industry and transportation sectors are the main sources of emissions in North America and Europe; while industrial and residential emissions are important causes of poor air quality in China. In general, larger, more developed countries have more emissions from transportation, while smaller and poorer countries suffer from more emissions from residential sources, such as high levels of harmful PM caused by the use of biomass (e.g. wood, crop waste, dried animal dung) in indoor cooking.
Outdoor Air Pollution Increases Annually
Increasing anthropogenic air pollutant emissions have led to rising ambient air pollution levels in many world regions. According to the World Health Organization (WHO), outdoor air pollution has increased eight percent annually over the past five years, meaning billions of people worldwide are now exposed to dangerous air. West and his colleagues estimated 2.2 million deaths per year are associated with ambient PM around the world, while an additional 500,000 deaths are associated with ozone exposure.
Though there has been much interest in the global burden of disease (GBD) and in the number of people who die due to air pollution exposure, West noted, only a few prior studies have looked at the relevant emission patterns on a global scale.
“Knowledge of these emission patterns can help guide policy as to what counter-measures to this global health hazard would be appropriate within the separate world regions,” West said.
Computer Model Puts a Fine Point on Emissions Data
A CTM using a coarse resolution is unable to distinguish the fine gradients in air pollutant concentrations, and can underestimate some PM-related mortality. A coarse analysis might, for example, put urban and rural data within the same grid box. A finer resolution, on the other hand, which the team used in the study, can confine data analysis to the urban area, where most of the population is concentrated. This urban area analysis helps provide a more exact picture of emission effects on the population.
West pointed out that most environmental engineering departments across the nation lie within a university’s school of engineering or of arts and sciences.
“What’s unique about our department is that we are located within the UNC School of Public Health,” said West. “Sitting inside the School of Public Health puts us in greater contact with people working on health-related issues and makes health and national and international health policy a stronger motivation for the work we do.”
Modelers, Engineers, and Health Researchers Span Discipline Divides
“I’ve been working on health-related problems for a decade and have seen a real growth in interest on the part of engineers and modelers to understand health better, driving more communication. Some of the divisions between people who study atmosphere and people who study health are breaking down.”
“The community is growing bigger,” West continued. “There is still a disciplinary divide, but it’s becoming more accepted in academia that a researcher can be working in more than one discipline. Here in my lab we’re using modeling tools that come from atmospheric science to do work that’s fundamentally about health and the global drivers of health.”
Given the potential of these powerful and sophisticated atmospheric modeling tools, West speculated: “By using and refining [our] methodology, people bridging disciplines will be able to understand the effects particular policies have had – or can have – on air pollution and human health, as well as on the environment at large.”
Silva RA, Adelman Z, Fry MM, West JJ. 2016. The impact of individual anthropogenic emissions sectors on the global burden of human mortality due to ambient air pollution. Environ Health Perspect 124:1776–1784;