Higher levels of ultrafine particles, such as near dense road traffic, resulted in heart function changes after only 5 minutes.
Researchers from the Helmholtz Zentrum München in Germany and the University of Rochester, NY, report their findings in the journal Particle and Fibre Toxicology.
Particulate matter, also known as particle pollution, is a complex mix of very small airborne particles and liquid droplets whose size is linked to their potential for harming health.
When describing air pollution, the US Environmental Protection Agency (EPA) distinguishes between coarse and fine inhalable particles.
Coarse particles, such as those found near roadways and dusty industries, are larger than 2.5 micrometers (µm) and smaller than 10 µm (commonly referred to as PM10); 10 µm is about one fifth of the thickness of human hair.
Fine particles, such as those found in smoke and haze, are smaller than 2.5 µm (PM2.5). Fine particles form as a result of forest fires or when gases from power plants, industrial processes and motorized vehicles react in the air.
Studies have linked exposure to inhalable particles - and fine particles in particular - to a number of health problems, including coughing, difficulty breathing, airway irritation, reduced lung function, irregular heartbeat, nonfatal heart attacks, chronic bronchitis, aggravated asthma and other illnesses, including some cancers.
Study focused on health effects of ultrafine particles
The new study focuses on a less well-researched particle size - the ultrafine particle - that measures less than 0.1 µm (PM0.1). Particles of this size are small enough to enter the bloodstream, with the potential to damage a number of internal systems that may be inaccessible to larger particles.
Lead author Prof. Annette Peters, head of the Epidemiology research program at the German Center for Diabetes Research (DZD), and colleagues investigated how ultrafine particles affected the heart in 64 patients diagnosed either with impaired glucose tolerance (IGT) or type 2 diabetes.
The participants wore devices that measured particle number concentrations in the air around them and recorded electrocardiograms (ECGs) of their heart activity as they went about their day-to-day lives.
As well as the data from the individual devices, the researchers obtained particulate matter measurements from a station that monitors air pollution in the area the participants lived in - the city of Augsburg in the southwest of Bavaria in Germany.
When they analyzed the results, the team found links between ultrafine particle levels and changes to heart rate variability - a feature of heart function that shows how the person's heart and circulation is adapting to current demands. Prof. Peters explains:
"Elevated concentrations of ultrafine particles, e.g. in dense road traffic, led to a change in heart rate variability of the participants after only 5 minutes."
The researchers also confirmed what other studies had found, for instance, that fine particles over the course of an hour - and noise - are linked to impaired heart function.
Currently no regulation threshold for ultrafine particles
Prof. Peters says they were alarmed by the results because ultrafine particles are generally everywhere in the environment and pose health risks for all of us, "but especially for people who already have an elevated risk for cardiovascular disease, such as the individuals with diabetes in this study."
She explains that the harmful effects of fine particles have already been established. In their study, they found evidence of potential harm at levels below the current EU threshold, which has been in place for 10 years.
However, due to lack of clear evidence, there is currently no threshold for ultrafine particles. Prof. Peters and colleagues hope this study will help to change this:
"We hope that with our data, we can substantiate the demands for threshold limit values and environmental standards in the future."
According to the EPA, ultrafine particles "are not specifically regulated but have a strong link to combustion and therefore are garnering special attention." In urban areas, sources of combustion gases include motor vehicles and generators.
Meanwhile, a recent BMJ review that analyzed 100 studies from 28 countries on the health effects of air pollution has established a link between short-term exposure to particulate matter and stroke. The researchers from Edinburgh University in the UK found stroke risk rose in line with increasing concentrations of both fine and coarse particulate matter.