"Chronic exposure to air pollution has been associated with various health-related illnesses, however few studies have related air pollution to cardiovascular disease," said lead author Demosthenes B. Panagiotakos, Ph.D., a biostatistician and epidemiologist at the First Cardiology Clinic at the University of Athens School of Medicine in Athens, Greece.
The researchers conducted the study in the greater Athens area from 1992 to 1997. They collected daily values of primary air pollutants - smoke, sulfur dioxide, nitrogen dioxide and carbon monoxide - from eight stations of the Ministry of Environment (Directorate of Air and Noise Pollution Control). They also collected data about the number of deaths due to heart disease and stroke.
They found a significant positive association between cardiovascular disease (CVD) deaths and several air pollutants. In particular, for every 10 micrograms per cubic meter (mg/m3) increase in black smoke, they observed a 4 percent increase of CVD deaths. Similarly, a 10-mg/m3 increase in sulfur dioxide was associated with a 5 percent increase of CVD deaths.
"The most important finding is that a 10-unit increase in carbon monoxide (CO) was associated with a 46 percent increase in CVD deaths," Panagiotakos said.
On further analysis, the researchers found that the average number of CVD deaths in the Athens area during the study period was 35 deaths each day.
Panagiotakos said the increase of 1-unit in CO levels might lead to two more deaths each day or more than 700 a year. In addition, CO levels roughly explained 3 percent of the observed CVD deaths during the investigated period.
The researchers said the values of the investigated air pollutants reached very high levels many times during the past decade. They attribute this to a rapid increase in population, especially since the 1950s, and the dramatic rise in motor vehicles and industries.
"Athens' greater area has more than 4.5 million inhabitants. Four-fifths of the population live in the urban center and one-fifth live in rural areas of the Attica region," Panagiotakos said.
He noted that his findings are consistent with results of other studies in Europe and the United States. It is well known that air pollution such as dust; gases and smoke are mainly generated by human activities. He added that changes in automobile emissions technology beginning in the late 1990s have helped to improve air quality in Athens.
"Our findings about CO are important because levels of CO are a very good indicator of primary pollution. In Athens, as well as in many other cities, the basic pollution source is traffic, and the most characteristic pollutant from traffic is CO," Panagiotakos said.
"During the past two decades, the average CO levels in the Athens area varied from 1 to 6 milligrams per cubic meter (mg /m3); however, CO values often exceeded the air quality standard of 10 mg /m3. The number of CVD deaths increased substantially as a result. "These health effects occur even at exposure levels below those stipulated in current air-quality guidelines, and it is unclear whether a safe threshold exists," Panagiotakos said.
"It is essential that public health authorities take further actions to reduce cardiovascular mortality in urban areas of the world, especially on days with elevated levels of air pollutants," he added.
The seasonal variations of air pollutant concentrations are at a minimum during the warm period and a maximum during the cold period of the year because of the central heating emissions, the increased traffic and industrial activities.
Co-authors are Christina Chrysohoou, M.D., Ph.D.; Panagiotis Nastos, Ph.D.; Christos Pitsavos, M.D., Ph.D. and Christodoulos Stefanadis, M.D., Ph.D.