Indoor vs. Outdoor Air Pollution: The Necessity of Improving Indoor Air Quality

Osaka, Japan seen from inside a round window. Small plant on windowsill.

Identifying and removing the sources of indoor air pollution, and thus improving indoor air quality, is just as important as the efforts to reduce the amount of pollution in the air outside.


By Ana Marković

The air quality analysis in Novi Sad, Serbia has been showing an excessively high amount of PM2.5 particles in recent months, averaging around 55.4, which is almost two times higher than the healthy limit. These particles are extremely small and light, which enables them to stay longer in the air, thus increasing the risk of the particles penetrating deep into the lungs and triggering respiratory problems. Prolonged exposure to high concentrations of PM2.5 is particularly dangerous for the elderly and persons who suffer from cardiopulmonary disease as it increases the chances of heart or lung disease and premature death. However, such high levels of air pollution pose a health risk for everyone and may cause respiratory problems in the general population. Staying indoors during such periods seems like an effective means of protection, but studies show that indoor air may be even more hazardous than the air outside.

The effects of outdoor air pollution

Outdoor air pollution remains one of the world’s largest health and environmental problems. According to a study conducted in 2017, outdoor air pollution was responsible for 3.4 million premature deaths globally. Older people are the most affected, due to the long-term exposure to the air pollution over their lifetimes.

The same study established the link between death rates and exposure to pollution, concluding that the death rate from air pollution is higher in countries that have a higher level of pollution, which is the case in a majority of countries in Africa and Asia. On the other end of the spectrum, most European, North American and Latin American countries have low levels of air pollution, and consequently a lower number of deaths caused by poor air quality.

However, the researchers also discovered that countries with high levels of pollution, such as Saudi Arabia, Qatar, and Kuwait also have a lower risk of premature death cause by air pollution, due to high healthcare standards. The study’s results show that low-to-middle income countries are the ones that are most gravely affected by air pollution, as good living standards also play an important role in reducing the risk of mortality from respiratory illness.

Cars line a street at night
Novi Sad, Serbia. Photo by Damir Omerović on Unsplash

The air inside can be harmful, too

Being exposed to environmental pollutants is a risk that sometimes can’t be avoided as it is a part of our daily lives. However, exposure to indoor air pollution is something we can reduce significantly, provided we are well-informed about it. In the last few years, there has been a growing amount of scientific evidence that shows that indoor air can be more polluted than the air outside in even the most industrialized cities in the world. According to the EPA, the levels of indoor air pollution can be two to five times higher than outdoor levels. Taking into account that people spend 90 percent of their time indoors, poor quality of indoor air poses a greater health risk than the outdoor air for many, particularly for those who suffer from respiratory or cardiovascular disease.

Sources of indoor air pollution

Indoor air pollution can be caused by various sources that release gases and particles into the air, such as stoves, furnaces, space heaters or central heating and cooling systems. Other sources that can lower the quality of indoor air include building materials, insulation that contains asbestos, furniture made of certain type of pressed wood, air fresheners, and household cleaning and maintenance products that contain solvents or pesticides. How much a single source is responsible for the overall indoor pollution in a home depends on the rate at which it releases pollutants as well as the level of threat to health posed by each type of pollutant. For instance, a malfunctioning gas stove can emit a higher concentration of carbon monoxide than the stove that is properly adjusted.

Indoor air quality can also be affected by smoking, high levels of humidity, and improper ventilation. Outdoor air carries out indoor pollutants out of the home, so if there isn’t enough outdoor air entering your home, the amount of indoor pollutants will increase to levels that may pose a risk to your health.

Improving indoor air quality

The most effective way of improving the air quality in your home is to identify and eliminate the source of the problem or reduce its emissions. One of the common sources of indoor pollution are gas stoves, which can be adjusted to minimize the amount of emissions. Asbestos is also a common problem in many households, so sources that contain this dangerous group of minerals can be sealed or enclosed.

Increasing the amount of ventilation goes a long way in improving indoor air quality. Opening windows and doors regularly and installing bathroom or kitchen fans if possible contribute to increasing the amount of fresh air that enters your home.

Green plants helping with indoor air quality
Plants may also help to improve indoor air quality.
Culture centre *Lab*, Novi Sad, Serbia. Photo by Dušan Tizić on Unsplash

Another popular tool for improving the quality of air in your home is an air cleaner. There is a wide selection of air cleaners available for purchase, ranging from smaller models to whole-house systems. However, it’s important to note that not all air cleaners are equally effective. Whether an air cleaner is efficient in purifying indoor air depends on its air-circulation rate and the ability to collect pollutants from indoor air. An air cleaner with a low air-circulation rate will not be effective even if it is an extremely efficient collector, and vice versa. To learn more about the use of air cleaning devices read EPA’s article on Air Cleaners and Air Filters in the Home.

Outdoor sources like pesticides and radon can also pollute indoor air. Since radon is an odorless and colorless radioactive gas, you can determine its presence in your home only by using specific devices designed to measure it, which are available for purchase. You can learn more on testing and controlling radon in indoor environment here.

Identifying and removing the sources of indoor air pollution is just as important as the efforts to reduce the amount of pollution in the air outside. It’s necessary to take part in improving the quality of the air in your home to minimize any potential health risk caused by air pollutants and ensure a healthy, fresh air inside.

Related: How Major Cities Around the World are Fighting Air Pollution

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