Yes, they are! At least three scientific studies have looked at the effectiveness of face masks for protecting against air pollution. The researchers concluded that the most important factor for mask effectiveness is how well the mask fit the face and is able to seal off particles.
Social distancing recommendations inform people to stay 6 feet apart from one another. But scientists are discovering that this may not be sufficient. This shows why it is so essential to wear a face mask when you are out in public settings.