Six Cities Study (the US) — Air Pollution and Mortality

When we meet with the smog (or hazy air), our first reaction tends to be because it is unsightly and it is foul-smelling, and not because it is harmful to our health. While we have much more knowledge about how harmful air pollutants are (especially small particulates such as PM2.5), back in the 1970s this was not always the general knowledge.

Let us not forget that it took a serious hazy event in 2013 for Singapore to include PM2.5 in its Pollutant Standard Index (PSI) too.

A guide to reading the PSI released by the NEA in 2014 (with PM2.5 included within the PSI readings). Retrieved from:

As such, the “Harvard Six Cities Study” is famous for being one of the first to look at the correlation between air pollution and mortality over a long time period, and which lead to substantive action taken by the US government to regulate fine air particulates. The study reported the mortality of 8,111 randomly selected residents from six different U.S cities — Harriman (Tennesse), Portage (Wisconsin), St. Louis (Missouri), Steubenville (Ohio), Topeka (Kansas) and Watertown (Massachusetts) — with the aim of estimating the effects of air pollution on mortality while keeping other risk factors under control. These randomly selected residents were recruited between 1974 and 1977, and had their medical and occupational history recorded. These participants were also subjected to lung function tests. Air quality from their surroundings is taken by both ambient air monitoring stations in their towns, and also from air sampling devices worn by some participants or such devices from their homes. These residents were contacted all the way till 1991 to determine their health status, while death certificates are collected for those who have passed away in order to find out what is their cause of death.

What the study found is that mortality due to lung cancer and cardiopulmonary disease is most strongly associated with levels of fine air pollutants. Many other researchers have published follow-up articles based on this research (which is neatly summarised by the article from The Pump Handle by Monforton (2012).

Just last year, 20 years after the follow-up research for the study ended (in 1994), the lead author of the original paper, D. Dockery, gave a brief overview on what changes there have been since the study was published. These include new standards put in place by the Governmental Protection Agency (EPA), and an improvement in both health and air quality in the six cities from the original study. Another important point he made is that the federal Office of Management and Budget found that the largest estimated benefit from all federal regulations in 2007, is the reduction of just one air pollutant — fine particulate matter. The impacts of the study not just includes new standards in place, but has also laid “a firm scientific foundation for regulatory policies” .

This “six cities study” and it’s subsequent follow-ups definitely paint a clear picture of what is at stake for air pollution, and the benefits that cities may reap (not just in terms of health) if they take active steps to decrease the amount of fine particulate matter in the air.


Dockery, D., Pope, C. A., Xu, X., Spengler, J. D., Ware, J. H., Fay, M. E., Ferris Jr, B. G. and Speizer, F. E. (1993). An Association between Air Pollution and Mortality in Six U.S. Cities. The New England Journal of Medicine. 329:1753-1759

Feldscher, K. (2014) Landmark air pollution study turns 20. Harvard School of Public Health — Featured News Stories. [Online] Retrieved from: [last accessed 3 April 2015)

Lauerman, J. F. (n.d). A Tale of Six Cities. Flue Cube. [online] Retrieved from: [last accessed: 4 April 2015]

Monforton, C. (2012) Public Health Classics: Assessing air pollution and health in six U.S. cities, researchers’ findings changed the air we breathe. The Pump Handle [Online]. Retrieved from: [last accessed: 4 April 2015]

National Environment Agency (2014) PSI (with effect from 1st April 2014). PSI. [Online]. Retrieved from: [last accessed: 3 April 2015]


Pittsburgh’s Air Pollution (1940s vs Today)

I saw this BuzzFeed article contrasting the difference in air pollution (through photographs) in Pittsburgh’s streets almost 70 years ago. (Do take a look!) The contrast is quite startling; seeing photographs of the hazy air (the outlines of buildings nearby are obscured) gives a better picture of just how severe pollution issues are in the past too.

While looking through the pictures, I felt quite happy that there is much progress for the better, and this made me wonder if it is possible for many highly polluted streets and regions to improve their air quality too. What is important to note is that measures take time — perhaps, we cannot expect air quality to improve overnight. But we can be hopeful that many decades later, there is a possibility of cleaner air.

Indeed, the Atlantic had used these pictures to tell netizens who are criticising Beijing’s air quality that it takes time, and Pittsburgh took close to a century to reduce the amount of smoke and soot particles in the air to the level it is at today. Contrast Pittsburgh’s development in the 19th century as the city, powered by coal, emerged as one of the main metalworks industries in the country with Beijing’s excessive coal powered power plants today.

This is Pittsburgh back in the 1940s. Source: [Last accessed: 1 March 2015]

After looking at these pictures, I have some thoughts (these are not necessarily referring to Pittsburgh and Beijing; I am thinking about many cities around the world in general):

1. The political will of the city/country’s authorities

After looking through the pictures, it might be tempting to say that severe air pollution around the world is acceptable for developing cities, and that they just need to be given a longer time to solve their air pollution issues because they are inevitable with industrial development. I think that it is unacceptable to say that just because other countries were able to pollute the air without much dire consequences (laws were not as strict as those today), one should be permitted to pollute the air as much as they would want to. It may be unfair for countries who are at the other end of the developmental ladder, but I feel that there is a responsibility towards not just a country’s own citizens, but citizens of the world once there is ample evidence and knowledge on tackling these issues.

That said, we should be aware of the unequal power relations on the world stage — would developed countries push the developmental ladder away from developing countries? Ideally, developed countries with the expertise and experience should provide their technological known-how for other countries to tackle the same problem they faced many years ago, but which country is entirely selfless to do that without any reservations or motives (settling a deal, etc)? I think not.

2. The situation may not have improved as much as we thought it had

For instance, back to Pittsburgh: it is reported in 2014 that the air quality is still bad despite improvements, due to shifts towards natural gas from coal-powered plants, with increases in unhealthy ground-level ozone. Soot and smoke particles may have declined, but many cities around the world are facing a new set of pollution problems which are less visible. PM2.5, carbon dioxide and nitrogen dioxide are just a few examples.


Hopey, D. (2014). Pittsburgh region still gets poor marks for air pollution. Pittsburgh Post-Gazette. [Online] Retrieved from: [Last accessed: 1 March 2015]

Madrigal, A. (2013). Aghast over Beijing’s Air Pollution? This was Pittsburgh not that long ago. The Atlantic. [Online] Retrieved from: [Last accessed: 1 March 2015]

Using public art to tackle pollution from urban runoff

Stormwater runoff is intensified after a precipitation event over, in particular, urban areas; the large amount of concrete walkways and streets reduces infiltration and percolation of precipitation into the ground. A good drainage system is essential to removing precipitation rapidly from urban areas to prevent flooding.

Unfortunately, that means that any pollutants on the streets are washed into the drains by urban runoff. These pollutants includes chemicals from motor cars such as motor oil and improperly disposed household cleaning products, and also physical waste such as plastic bottles and other rubbish thrown onto the streets. These storm water often drains directly into natural water sources.

To tackle this problem, the city of Reno, Nevada, started a campaign, “Storm Drains are the Mouth of the Reno”, in August 2013. Painting attractive art on storm drains (these are definitely a lot more attractive than the metal storm drain markers) , authorities hope to educate residents on the difference between storm drains (which leads directly to water sources without going through treatment plants) and the sewage systems so that residents will be more aware of the potentially disastrous impacts of polluted storm drainage on the Truckee River and its ecosystem. This is done by painting various marine creatures over storm drains so as to “humanise the storm drains”, prompting residents to think twice before disposing rubbish or other chemicals into storm drains. The message is simple: “if we wouldn’t put radiator fluid, oil, or glass in our mouths, we shouldn’t put them in our river’s mouth.”

I thought that the use of prominent and striking public art is a good way to catch the attention of residents. Coupled with poster and social media campaigns, this campaign by the city of Reno seems promising (according to their video, which can be found below, they managed to reach 72% of their target audience through more than 100,000 shares over social media). Of course, it must be noted that outreach does not necessarily indicate the success of the campaign. More time is needed to observe if awareness did translate into education, and education did translate into action. I also had some doubts about the use of paints over drain covers — it seems to me that that chemical compounds from paints will contribute to urban runoff as pollutants too. Nonetheless, I thought that the campaign is definitely something ingenious and creative, and will be an effective tool for raising awareness. Perhaps the focus will shift more towards actively reducing the source of pollutants once more people are aware and understood the importance of doing so!


StormwaterPA (n.d.). Public Art takes on Pollution. [Online] Retrieved from [Last accessed: 27th January 2015]

Town of Truckee, California (2009). Stormdrain Markers. [Online] Retrieved from [Last accessed: 27th January 2015]

United States Environmental Protection Agency (2003). “After the Storm”. [Online] Retrieved from [Last accessed: 27th January 2015]

Storm Water Pollution Facts. [Online] Retrieved from [Last accessed: 27th January 2015]