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How an air pollution study from 1993 changed history

In the 1970s, London's smogs became a distant memory. The last big smog had occurred in 1962, and it looked as though the problems of air pollution in the cities of Britain had been resolved. The world's leading air purification division of the Medical Research Council at St. Bartholomew Hospital in London has been closed. It had done its job in the eyes of the government. It just was not necessary anymore.

At the same time that Britain gave up research capacity, Doug Dockery and his colleagues in the US began a new kind of study to investigate the health effects of air pollution. When it was completed and published almost twenty years later, Dockery's revolutionary insights changed our view of air pollution even further than the London smog of 1


Dockery did not start as a doctor or healthcare professional. He completed his first degree in physics. Subsequently, he gradually explored meteorology and environmental science as the environment around us affects our health. Dockery and his team worked at the Harvard School of Public Health in Boston. The school was founded in 1913 to train health professionals. The work of the school has influenced our lives all over the world. Starting with infectious diseases, their researchers invented the iron lung to keep polio victims alive before offering a Nobel Prize-winning vaccine in the 1950s. They also led to the eradication of smallpox. In parallel with these achievements, the school can also list the air pollution work of Dockery and his team, which started with the Six Cities study. As of 1974, the Six Cities study involved 8,111 individuals selected at random from selected locations. These were Watertown in Massachusetts, parts of St. Louis, the steel town of Steubenville in Ohio, and the less polluted Portage towns in Wisconsin, Harriman in Tennessee and Topeka in Kansas. The participants completed questionnaires on weight, height, smoking habits, occupation and medical history. Everyone had their breath tested. Then the Dockery team sent a postcard every year to find out if they were dead. If there was no answer, they sent an investigator to talk with family, friends, and neighbors to find out what had happened. This lasted sixteen years. During this time 1,930 participants died. There was nothing out of the ordinary, but it was important who died and where they lived. The inhabitants of Steubenville and St. Louis died faster than the inhabitants of Topeka and Portage. The number of smokers, the body mass index and other factors that affect people's health were taken into account, but there were still differences between the cities that could not be explained. However, when these differences were recorded against particulate pollution in each city, an unusual pattern developed.

Think of the lab tests you performed at school and in the lab results you drew on graph paper. There would always be a few shaky points that did not quite fit. They would expect a sixteen-year experiment to contain many variables and anomalies, but the team found a nearly straightforward relationship that has become one of the best-known actions in air pollution science. It's shown below with the original data from Dockery's team.

People in Steubenville died almost 30 percent faster than those in Portage because of the extra air pollution they were breathing through traffic and the industry around them. And people not only died of lung problems, but also of heart problems, just like those of the 1952 London smog. In fact, this was not the first study to show that daily exposure to modern air pollution harmed our health, but other studies were less clear in their outcomes.

The publication of the Six Cities study in 1993 was quickly followed by another that looked at the mortality rates of a large group of US citizens who were being prosecuted to review the development of cancer. They too died early because of the particulate pollution they were breathing. Suddenly, we realized that the impact of modern air pollution on health was greater than anyone could imagine. Although the cleanest of the six cities was considered, the effect of air pollution was still clear. Our air had to become cleaner. cleaner than the air in Portage. New efforts were needed, not only in traditionally polluted places like the steel city of Steubenville, but everywhere.

To protect human health and set standards for the air in our cities, new pollution laws are needed. It was clear that industry and vehicle manufacturers, to name but two sectors, needed to do much more to eliminate the pollution they caused. However, as Arie Jan Haagen-Smit discovered over forty years ago, interest groups fought tooth and nail.

The publication of the 1993 Six Cities study met with controversy and debate. As with the twenty-first century climate change problems and the European acid rain problems of the 1970s, those who did not like the results were challenged. How could Dockery be sure it was the particle pollution that caused people to die early? People were breathing a lot of air pollutants, not just one. (In fairness, other pollutants were measured in the Six Cities study, but their links to death rates were far from clear.) The Dockery team was unable to measure every possible pollutant. Could one of them have been the cause? The particles in each city came from very different sources and had different chemical compositions. How could they all have the same effect? Association is not the same as cause; Just because people died in the more polluted cities earlier did not mean that air pollution actually led to deaths. * Could the difference in mortality be due to other differences between cities? Maybe it was weather differences or the number of smokers? Did the researchers just make a mistake? How can tiny amounts of particles in the air still cause problems? Was it really the mass of these particles in the air or their number? If the government can not be completely sure, it should not unduly harm corporate profits. Less prominent in these debates were the voices, which pointed out that hundreds of people died in these cities and immediate action was required. Delay would mean more people die prematurely.

One solution would be to re-run the Six Cities study to prove it a second time. However, this would take at least sixteen years, plus time for analysis. During this time, the industry could continue as before. The US Congress took part in it, and it was decided that a separate and independent group of researchers would go over the data with a fine comb and repeat the original work. Finally, in 2000, the original results were confirmed. The everyday particle pollution that we breathe was and is the shortening of our lives.

The Six Cities study has triggered another evolution in air management. We have moved from the 1950s approach to managing sources to new air pollution laws that set standards for the air itself. Standards and limits have been established in the United States and Europe, and the World Health Organization has established guidelines.

The effects of the Six Cities study have not stopped here. Between 1990 and 1998, another 1,394 of the original 8,111 people died. The researchers recalled the controversy of the original study and returned to all survivors to interview them, weigh them up and find out their current health and smoking habits. Again the same linear relationship between survival and particle pollution was noted, but this time there was better news as well. In the 1990s, measures to improve air pollution started. Particulate pollution has been decreasing throughout the 26-year study period and the biggest improvements have been observed in the most polluted cities. In Steubenville and St. Louis, particle pollution in 1998 was less than two thirds of the value measured twenty years ago. At the other end of the scale, Portage and Topeka showed little or no improvement. Improving air pollution also improved the survival rate. (The researchers found a similar result when they reviewed the survivors of the Six Cities in 2009 again.) Air purification worked, and at least some of the harmful effects were reversible.

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