You may enjoy using wax melts to perfume different rooms while you’re at home. But, did you know these products can pollute the air?

Purdue University Assistant Professor Nusrat Jung says wax melts can expose users to a “heavy dose of air pollution.” While you may think they are significantly better for the environment than traditional candles, Jung’s research indicates that this is not the case.

Essentially, they are often “heavily laden with…reactive chemicals and generate large amounts of nanoparticles.”

Jung notes that people might be surprised by how much pollution can be caused by the everyday products. This can be especially concerning in indoor spaces, where Americans spend about 90% of their time.