Shopping malls have become central to city life in the past decade, and not just for shopping; the food courts offer of a delicious range of cuisines, there are often events, art exhibitions and activities for children. Shopping malls are a social hub, somewhere you will spend time with family, friends and colleagues. It is no surprise that many of us spend a huge proportion of our free time in such establishments. Financial Times reported that 40.9 % of the urban population visit malls visit at least once a week. Have you ever thought about the health impacts of walking around or eating in a shopping mall? I expect not, because, naturally we believe that once inside, we are no longer exposed to the elements.

At AirVisual, we have challenged common assumptions by using our Node to analyse the levels of particulate matter you would be exposed to in different shopping malls and comparing this to the levels outside. Particulate matter is one of the main pollutants responsible for respiratory problems, in particular those particles smaller than 2.5 micrometres in size (PM2.5). Pollution masks are designed to protect us against PM2.5; however, when we enter shopping malls, we usually remove our masks, right?

A number of shopping malls in the Chaoyang district were investigated. These malls host everything from local stores to high end designers, and are visited by a huge volume of both locals and tourists on a regular basis. Measurements were carried out on various high pollution days and a comparison was made between the air quality directly outside and inside the shopping malls. Some shopping malls have made huge investments into air filtration and purification systems, but in such vast spaces, are they effective enough?

Results

Results show that, on a high pollution day, we may not be that much safer from the pollution inside as compared with outside. Whilst there is some variability between shopping malls, on average individuals are exposed to between 12 % and 28 % less PM2.5, when inside a shopping mall. The greatest reduction measured was 54 % and in some locations, the levels were the same as outside.

So, what does this mean? On a highly polluted day when the AQI outside is 220 it is classified as Very Unhealthy , it is possible that the AQI inside a shopping mall will be no less than an AQI of 176, which is still classified as Unhealthy . Both these levels fall under the values where it would be recommended to wear a pollution mask, so on a day such as this, the recommendation would be to wear a mask inside. In comparison, when the AQI outside is 70, it is classified as Moderate , it is possible that the AQI inside a shopping mall will be no less than 56, which would carry the same classification of Moderate .

It was also noted that if you go to the food court of a shopping mall, your exposure to PM2.5 is much higher than around the rest of the mall; at times the levels observed near restaurants exceeded the levels outside.

Why is this the case?

Air conditioning devices are widely used for cooling, and when our local environment is cooler, we automatically feel a lot better. This does not, however, mean that our local environment is free from pollutants. Air conditioning units take the air in the room, which may be as polluted as outside and then they cool it. Some air conditioning units are fitted with filters which remove larger impurities from the air, but this reduction is minimal in terms of the harmful PM2.5 which is present. For removal of pollutants from the indoor air, air purifying systems are needed. These can be very expensive for shopping malls, and even in malls which have systems fitted, their effectiveness may be variable.

What should you do?

The key recommendations arising as a result of this research are that on high pollution days, we should continue to wear our pollution masks in shopping malls, as the air inside may not be as clean as we assume it to be. Alongside this, we should be more wary when exploring the food court, once again wearing our masks to reduce our exposures to the particulates produced during cooking.

Pollution is a problem which is effecting us all on a daily basis, this research shows that we need to collectively challenge our common assumptions of situations in which we are more or less exposed to pollutants. Awareness inspires change; being aware and wearing your mask inside will encourage investment into more air purification systems being installed in locations such as shopping malls.

Malls investigated during August 2016: Raffles City Mall , Sanlitun South, Sanlitun North, 3.3 Mall, City Mall , Gongsan Mall, Park View Green, The Place, China World Mall and Kerry Centre.