Scientists again warned about the danger of air pollution with fine dispersed solid particles. According to a group of researchers from Britain, China and the United States, elderly residents of megacities should carefully choose places for long walks around the city. The air of streets with active traffic can negate all the benefits of physical activity, so it's better to spend time in a park or square. The same is true for people of any age who suffer from heart or lung disease.

The study involved 119 Londoners over the age of 60. In 40 of them, chronic obstructive pulmonary disease (COPD) was diagnosed, 39 - ischemic heart disease, another 40 people did not have chronic diseases. Representatives of the first two groups did not experience acute conditions within six months before the start of the study. At least a year before the start of work, none of the participants did not smoke.

The researchers divided the participants into two groups and asked them to go for a two-hour walk around London. One group was walking in Hyde Park, the other was walking along the busy Oxford Street in the area where only buses and taxis can enter. At the same time, scientists studied the concentration of hazardous substances in the air in these areas. They measured the level of nitrogen dioxide, as well as the concentration of fine particles PM10 and PM2. 5 are solid particles with a diameter of up to 10 and up to 2.5 micrometers. On Oxford Street, the level of pollutants was expected to be higher than in the park. After returning from a walk, the participants of the work were examined. A few weeks later, the test was repeated with the same conditions.

Walking among the trees was useful: within an hour visitors to Hyde Park increased the vital capacity of lungs and expiratory volume, during the day after a walk, these rates continued to grow. However, those who walked along the street, they grew slightly, and in the group with COPD - decreased. Also, COPD patients who visited Oxford Street often complained of coughing, phlegm, wheezing and dyspnoea. A walk in the park reduced arterial rigidity (stiffness) - one of the markers for the development of cardiovascular diseases. At the same time, walking along the street increased this figure.

Commented one of the authors of the study, Kian Fan Chung: "For many people, including the elderly and those suffering from chronic diseases, walks are the only available type of exercise. Our study allows elderly people to recommend walks in the green areas of the city, away from under construction and transport pollution ".

The study is published in The Lancet, notes naked-science.