Green roof top reduces indoor air pollution !!

More often than not we talk about outdoor  air pollution  and in this regard   smog, power plants and emissions from cars and trucks, etc come to our mind first. We either ignore or fail to give  serious attention to  air indoors  that can be polluted too.  Air pollutants  in the air are quite harmful and particles contaminate the air indoors.
The crux of the problem which many of us are not aware  of is indoor air pollution is  real and  equally dangerous because the indoor air is far more concenrated with  pollutants than outdoor air; they will be circulatingwithin the four walls in a close environment. More than   2.2 million people die annually due to indoor air pollution as oppossed to  500,000  annual deaths from outdoor air pollution it is mentioned. When it comes to  many sources of indoor air pollution, they vary among  developed and developing nations. 
In particular, in developing countries, the sources are well prounced and  the resultant air pollutuion  has a far greater impact.  The main reason is for cooking, heating,  wood, charcoal and animal dung are used  inside homes as fuel. If the cooking area does not have proper  ventilation to allow the pollutants to escape, the people inside the house  will be breathing in carbon monoxide and other dangerous contaminants. Persistent indoor  air pollutants from these sources cause  serious human health issues leading to  such as pneumonia, bronchitis, cancer, heart disease and asthma.  It is estimated that every year 1.6 million people  die from indoor air pollution   caused  by old traitional method of cooking . More than half of the population of developing nations  depend on the old method of cooking. 
Indoor air pollution

As for developed nations, the main indoor pollutants are   tobacco smoke and radon The latter is a radioactive gas that comes from the natural breakdown of uranium in soil, rock - both outcrop and polished one  and water. When the uranium breaks down, the radon gas seeps up and can get into buildings. Being  colorless and odorless, dectection is impossible and is dangerous. besides,  volatile organic compound is equally dangerous. Mention may be made of  perfume, paint, plastic, household cleaners, adhesives, furniture, carpet, paper,etc.  Even if  you do not smoke, secondhand smoke can cause many of the same health problems as directly inhaling from cigarettes - things like lung cancer, emphysema, asthma and heart disease.  It is estimated that there are as many as  4,000 chemicals  in use and  a large number of which are carcinogens, or cancer-causing chemicals.
Indoor air pollution.

Can the the indoor air quality of commercial buildings be improved by way of cutting the amount of ozone coming into the buildings from the outside? The new study by researchers at  Portland State University, Oregon, USA  answers  in the affirmative.  Green 
roofs -- roofs that are planted with vegetation  will do the trick - improve the indoor air quality. The researchers point out the environmental bebefits of roff-top green are reduction 
in carbon dioxide, urban heat and storm-water runoff.  What the researchers did was the university's  departments of Mechanical and Materials Engineering, Biology and the  Honors College,  chose the roof of  a big-box retail store in North Portland  and set up measuring devices To make comparitive studies, they split  the area  between a green roof and a more conventional white membrane roof.  They measured the air coming into the building from outdoor intake vents  from the green roof snd unplanted roof.  Surprisingly they  found that the air coming in from the green roof area had modestly lower ozone levels than the air coming in from the unplanted area. They noted that the vegetation trapped and filtered the ozone in the outdoor air.
The key factor is  dry deposition,  the trapping effect -  a process  in which airborne particles collect or deposit themselves on solid surfaces.  Obviously, it is a natural process  that is key to removing pollutants from the atmosphere. Though the study was conducted just for two days, research  on a long term basis will further reveal the  benefits of  green  roof top on indoor pollution  and the role played by pollutants as well as ozone.
Story Source:
Materials provided by Portland State University. Note: Content may be edited for style and length.
Journal Reference:
Pradeep Ramasubramanian, Olyssa Starry, Todd Rosenstiel, Elliott T. Gall. Pilot study on the impact of green roofs on ozone levels near building ventilation air supply. Building and Environment, 2019; 151: 43 DOI: 10.1016/j.buildenv.2019.01.023