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Despite widespread support for environmental legislation and technological improvements in air quality in the developed countries of Europe and North America, inhabitants of large cities there still suffer from increased risk of early death, heart or lung disease from pollution.

Two weeks ago Professor Joel Schwartz of Harvard University and Professor C. Arden Pope of Brigham Young University in Utah, two of the world's leading experts on the connection between air pollution and health, came to Israel as guests of the Environment and Health Fund.

In an interview with Haaretz, Pope said that even after a long series of measures to deal with problems of air pollution, an American living in one of the large urban centers is subjected to significant health hazards as a result of exposure to pollution.

"A person who lives in a city where there is heavy air pollution has a chance of coming down with heart and lung diseases that is greater by 10 to 15 percent than that of someone who lives in a town with little air pollution, and the situation is very similar in Western Europe," said Pope.

"According to one estimate, each year about 100,000 people die because of air pollution. Of course, in developing countries the situation is even worse."

According to Pope, scientists have known since the early 1990s that relatively small changes in air pollution suffice to cause a significant increase in early mortality or morbidity rates.

In recent years innovations have been made to better understand the mechanisms in the body that cause damage to various systems after exposure to pollution.

The main problem in most of the world is exposure to microparticles that carry various kinds of pollution.

Because of their tiny size (under 10 microns), these particles infiltrate deep into the respiratory system and various blood vessels.

Vehicles, power stations and industrial plants have all been identified as major contributors of microparticles

These days cars are cleaner and emit fewer particles, but because of the rise in the number of vehicles and the number of trips, the level of pollution is still high.

According to Pope, the polluting particles contribute to the development of infections and inflammations in the lungs and the blood vessels.

"The infections and the inflammations in the lungs affect all the body's systems. They increase the risk of damage to the heart, including heart attacks," he said.

Exposing the risks

This is not a matter of obvious causality. For a long time scientists were not certain that air pollution caused damage to the heart similar to damages caused by food and smoking.

However, after years of watching different groups of patients and performing blood tests and experiments on animals, researchers were able to confirm the damage it does.

The infiltration of the particles causes the development of vascular sclerosis - one of the developed world's biggest killers - and of many other kinds of damage to the heart and lungs, including changes in the heartbeat, decreased pulmonary functioning and the development of arterial blood clots.

The damage to the body can result from short-term exposure such as high level pollution that affects the person exposed to it within a few days, or from cumulative damage over months or even years.

Cumulative damage can also be caused by exposure to levels of pollution that fall inside safe standards set by authorities.

According to Pope, in a survey of heart patients in the United States (a study in which he participated), it was found that those most sensitive to short-term exposure were those with preexisting problems in the blood vessels and the heart.

"Exposure in the long term is one of the factors that accelerate and lead to the development of such problems, but it is clear that this is not only a matter of exposure to air pollution and that there are other factors than can exacerbate the problems," he said.

Other factors that influence how much pollution is in the air are climate and geographic configurations.

Inhabitants of cities that are located in valleys suffer more from air pollution, because the topography locks the pollution into the levels of the atmosphere and makes it difficult to diffuse.

A recent report by the European Environment Agency notes that in the Alpine valleys, a region that is supposed to be both green and clean, there is often pollution in high concentrations that has spread from the large urban cities and has been locked into the valleys.

Despite all the efforts, said Pope, many people are still dying from air pollution even in countries with advanced environmental protection and public health programs.

"But there is also an optimistic side," he said. "In recent years, much has been done to decrease morbidity and mortality. This is a factor that can be controlled and it is possible to bring about further significant improvements."

Preventing air pollution does not come cheap, though, since decreasing pollution requires a large economic investment on the part of the energy and automobile industries.

Pope, however, notes that according to studies carried out in the United States, it makes a good investment, in part because of the savings on health expenditures.

Ethical quandaries also abound in the field.

"It is necessary to relate not only to the economic costs of preventing air pollution," he said. "It must also be asked whether it is ethical to allow pollution that harms poor and sensitive populations.

"These are populations that very often do not enjoy all the material benefits of the society in which we live."