A study published in August 2025 in the Journal of the American College of Cardiology suggests that using an air purifier with a HEPA filter in homes near highways may help lower systolic blood pressure in individuals with elevated readings. The study involved 154 adults aged 30 and older, with an average age of 41, who lived near highways and were not taking medication for high blood pressure. Participants used a HealthMate air purifier with a HEPA filter for one month and a similar device without an effective filter for another month. The devices ran nearly all the time, placed in bedrooms and living rooms. Results showed that systolic blood pressure — the top number in a blood pressure reading — dropped by an average of 2.8 mmHg when participants used the HEPA filter. In contrast, systolic pressure rose slightly by 0.2 mmHg when they used the less effective device. Diastolic blood pressure — the bottom number — remained largely unchanged. The effect was only seen in people with systolic pressure of 120 mmHg or higher, not in those with normal or lower readings. The study points to PM2.5, tiny particles less than 2.5 micrometers in size, as a key factor. These particles, often from vehicle emissions, can pass through walls and enter the body. Once inhaled, they may trigger the sympathetic nervous system, raising heart rate and causing blood vessels to narrow. Over time, this can lead to changes in artery structure and function, contributing to high blood pressure. HEPA filters are designed to capture at least 99.97% of particles as small as 0.3 micrometers, including PM2.5. This study suggests that reducing exposure to these pollutants in the home could help lower blood pressure in those at risk. However, the researchers emphasize that air purifiers should not replace standard treatments like exercise, a healthy diet, or prescribed medications. Instead, they may offer an additional option for people living in areas with high air pollution.