What’s the Link Between Indoor and Outdoor Air Quality?

Indoor and outdoor air quality both have major impacts on our daily lives and long-term health.

While indoor and outdoor air may seem completely separate, they are more interconnected than you may realize. Understanding this connection can help you take action to improve your indoor air quality and stay aware of outdoor air quality.

Why Indoor and Outdoor Air Quality Matters

When we think of natural hazards, many people think of things like storms or intense heat or cold. The air we breathe can be just as dangerous as many of these other natural threats, though. In fact, since the industrial revolution, air quality has been a major public health concern. This is especially evident in urban areas where industrial activity clogs the air with pollutants.

Outdoor air quality threats include low-level ozone, particulate matter, smoke, lead, carbon monoxide, nitrogen dioxide, and sulfur dioxide. Exposure to polluted air can lead to serious health issues, including lung infection, cardiovascular disease, and cancer, as well as developmental issues in children.

The World Health Organization estimates that as of 2019, 99% of the global population is living in areas that don’t meet healthy air quality standards. This means it is likely that you are living in an area where you could be exposed to outdoor air pollution.

This doesn’t necessarily mean it is always safer indoors, though. Outdoor air quality can pollute indoor air quality as well.

The Threat of Outdoor Air Pollution

If a building is sealed off from the outdoors, doesn’t that mean you’ll be safe from outdoor air pollution? Not always. In fact, outdoor pollution frequently finds its way into homes and buildings. The degree to which indoor and outdoor air quality match up depends on the type of pollution at hand and the ventilation system of the building.

For example, in certain regions of China, particulate matter air pollution levels are so high that indoor air is just as polluted as outdoor air. This is a clear indication that indoor and outdoor air quality are closely related. When outdoor air becomes polluted enough, ventilation systems will struggle to keep up with it inside.

Filtering out polluted outdoor air is extremely important but also quite difficult. Think about a house, for example. Outdoor air can get in through doors, windows, cracks, vents, and just about any opening no matter how small. Every time you open your door, you are letting in some amount of polluted outdoor air.

Air pollutants are typically not visible to the naked eye, either. The house’s ventilation system will try to clear out these pollutants, but there’s only so much it can do. This is especially true given that the ventilation system needs to pull in air from outside to be filtered and cycled through the house. So, the higher the outdoor air pollution concentration is, the more difficult it will be for the ventilation system to effectively filter out pollutants from indoor air.

Is Indoor Air Quality More Dangerous?

If outdoor air quality can pollute indoor air quality, does this mean indoor air pollution is just as dangerous as outdoor air pollution? Possibly. In fact, indoor and outdoor air quality are so closely tied that in some ways poor indoor air quality can actually be more dangerous than outdoor air pollution.

In addition to outdoor pollutants, buildings have their own set of dangerous pollutants, including chemical contaminants such as paints or varnishes, viruses and bacteria, pet dander, and fumes from cooking and appliances.

The major problem that indoor air quality suffers from is contained air. In your home, office, school, or any other building, the indoor air is contained within that space and some of it will often get cycled through the ventilation system multiple times. If the ventilation system itself encounters issues, such as moisture or debris buildup, the indoor air can become contaminated with bacteria, spores, and other biological pollutants.

The U.S. Environmental Protection Agency estimates that Americans spend 90% of their time indoors today. So, the risks of unhealthy indoor air are serious. While indoor air pollution does not significantly affect outdoor air pollution, indoor air quality suffers further from poor outdoor air quality. Luckily, there are a few ways that you can take action to improve the quality of the air you breathe every day.

Cleaning Both Indoor and Outdoor Air

Improving the indoor and outdoor air quality you are exposed to is all about awareness and consistent healthy actions.

You may not be able to control the outdoor air quality in your area, but there are tools you can use to monitor it. For example, there are many smartphone apps that can give you live air quality updates in major urban areas. If you’re located outside a major city, you can also try this DIY weather station that uses an open-source AI to predict local air quality.

If you know the outdoor air quality, you can prepare accordingly, just like with the weather. On days when low-level ozone is more intense, for example, you can reschedule any outdoor activities. On these days, you’ll also want to keep doors and windows closed to minimize the outdoor air pollution leaking inside.

You have much more control over indoor air quality. Maintaining healthy indoor air is not a spring cleaning kind of activity. You have to take action every day to keep your indoor air clean.

Small habits can significantly improve your indoor air quality over time. Regularly cleaning and vacuuming your home, furniture, and bedding is a good first step. Even if you don’t have pets, surfaces all over your home can accumulate dust, allergens, and debris that contribute to poor air quality.

Additionally, it’s important to maintain your home’s ventilation system, if you live in a house. This includes regularly changing air filters and getting your HVAC system inspected at least once a year. Pollutants that accumulate in ventilation systems will be nearly impossible to see without having a trained professional actually take a look inside your vents.

You may also want to move your houseplants outside. While many believe that house plants help clean air by releasing oxygen, experts assert that plants actually cause more harm than good. They can contribute to the growth of mould that pollutes indoor air, which is a serious health threat. It may also be a good idea to get an air purifier, especially if you have pets. This will help counteract any minor pollutant sources and improve your indoor air quality.

Healthier Indoor and Outdoor Air Quality

Indoor and outdoor air quality are closely tied to one another. As outdoor air quality continues to worsen around the world, indoor air quality will suffer, too. We can take steps to improve our indoor air quality, but tackling outdoor air pollution is more difficult. Climate initiatives, like reforestation and carbon capture, will gradually help improve outdoor air quality, but there are ways everyday people can help.

Transportation is one of the leading causes of air pollution. So, consider carpooling, using public transit, or walking when you need to go somewhere. Just like cleaning indoor air, small and consistent healthy actions can make a big difference in the quality of the air we breathe.