Cleaner air results in a few more months of life. Can you extend your lifespan through an abundance of indoor plants as well?

An example of a bus in Seoul running on natural gas. The entire fleet of buses is expected to be converted to natural gas by next year. (Written on the bus you can see 쾌적한 도시환경 - 천연가스가 만들어갑니다 = A pleasant city environment; natural gas is making it happen)

That's the gist of this article here an a study that compared average lifespan with the air quality in the locations where people were living, and over the long term as well as air quality began to improve in the US:

Dramatic improvements in U.S. air quality over the last two decades have added 21 weeks to the life of the average American, researchers reported on Wednesday.

Reducing fine particles given off by automobiles, diesel engines, steel mills and coal-fired power plants have added as much as 15 percent of the 2.72 years of extra longevity seen in the United States since the early 1980s, they wrote in the New England Journal of Medicine.

One interesting part is how much smoking has to do with it:

Changes in smoking habits are the biggest reason why Americans are living longer, said Arden Pope, an epidemiologist at Brigham Young University in Utah who led the study.

Here's how it works in detail when you take a look at the numbers:

Using life expectancy, economic, demographic and pollution data from 51 metropolitan areas, Pope and his colleagues found when fine-particle air pollution dropped by 10 micrograms per cubic meter, life expectancy rose by 31 weeks.

What I'd be interested in seeing is how much control a person living in a big city has over the air he/she breathes in terms of bringing in plants to change the air quality inside, where we spend most of our time anyway. When living at home at Canada my brother was studying to be a botanist and had his room completely full of plants along with a huge sun lamp as the room was in the basement and there was no real sunlight, but with the huge number of plants the place was no different than being in the midst of a forest and I would often go down there to nap if I felt the need for oxygen. So let's say you're living in a large city like Seoul, but have a setup within your house like that; does that counteract the effects of living in such a large city, or does simply having to go outside daily result in worse health than if you were in a city with better air regardless of the environment you've created indoors?

Edit March 22: at long last, the answer!