If you’re concerned about climate change, you’re probably already aware of the negative environmental effects of increasing carbon dioxide levels. CO2 is a greenhouse gas, and because it traps additional heat in the atmosphere, it’s a primary driver of climate change and rising global average temperatures. Furthermore, too much CO2 in our atmosphere contributes to ocean acidification: the ocean absorbs about one-quarter of all CO2 emissions. Overall, all of this CO2 being released is contributing to melting ice caps, rising sea levels, and extreme weather events around the world.

But how does CO2 affect you personally? Just as it can affect our planet, it can also affect the health of human beings. This may come as a surprise even to those who are informed on climate change, because up until a few years ago, researchers weren’t sure how rising CO2 levels could harm our health. But new research has revealed some frightening trends.

Average CO2 levels indoors have always been higher than levels outdoors. This is because buildings are sealed off and don’t always have fresh air from outside flowing through. Furthermore, having a lot of people packed into a smaller, enclosed space will always result in increased CO2 levels. Studies have long shown that people who were exposed to high CO2 levels indoors could suffer negative effects, primarily decreased cognitive functioning—but it was presumed that this was merely correlation, not causation. Buildings with higher CO2 levels were poorly ventilated, meaning the air quality was simply lower, and it was expected that the shoddy ventilation was the cause of the problems, while the CO2 level was basically just a neutral indicator.

However, a groundbreaking Harvard study, “Is CO2 an Indoor Pollutant? Direct Effects of Low-to-Moderate CO2 Concentrations on Human Decision-Making Performance,” revealed that the CO2 itself was actually the root of the problem. The researchers raised CO2 levels in buildings while keeping all other variables consistent. They found a marked difference in cognitive functioning and saw that the increased CO2 exposure had a negative impact on productivity, learning, and test scores.

Why should you be concerned about this now? Throughout most of human history, people spent plenty of time outdoors, and their dwellings were relatively open and well-ventilated. CO2 levels fluctuated between 180 to 280 parts per million outdoors and perhaps hovered a bit higher indoors. But today, outdoor CO2 levels are reaching around 400 ppm, and in major cities, it can easily hit 500 ppm because of increased emissions from traffic. How about indoors? CO2 levels can range from 700 to 1000 ppm or even higher in many buildings. Humans have never been exposed to such high levels of CO2 for extended periods of time like we are today. And researchers are now finding that the negative cognitive effects start to kick in around 600 ppm.

And we are only going to continue releasing more into the atmosphere. Currently, CO2 levels are rising by about 2 ppm per year, which may not sound like a lot, but the rate of increase is speeding up. Without taking any action to curb emissions, we could have levels of 910 ppm outdoors by 2100, and even if we follow the guidelines set out by the Paris Accords, we would hit around 675 ppm outdoors by 2100. That would be unprecedented, and we have no idea how sustained exposure to those sky-high outdoor levels would affect human health—but it’s safe to assume that it would be very detrimental.

Is there any way that you can protect yourself from exposure to high CO2 levels? When you’re outdoors, it’s out of your control, but it is possible to lower the CO2 level in your own house. And some changes are quite cheap and simple.

First, make sure that screens are installed for your windows and doors, and keep them open as often as possible to let the fresh air in! If you’re using a fan for these hot summer months, place it in front of an open window so that it pushes the air to circulate through your house. Make sure that your HVAC system is well maintained—getting it inspected and cleaned every year or two is a smart idea. And finally, keep it green by picking up some indoor plants from your local farmer’s market or garden center. Plants take in CO2 and release oxygen, so they act as natural filters. This isn’t a problem that we can solve as individuals alone—we need political leaders to take action on emissions and pollution—but we can make some easy changes that help us stay healthy in the meantime.

Also by Jane: Longyearbyen, Norway, The Fastest Heating Town On Earth, Shows Why May Be Our Future

Democratic Candidates’ Positions On Climate Change, Simplified

Get more like this—Subscribe to our daily inspirational newsletter for exclusive content!