This study by UNEP and the Life Cycle Initiative, reviews five scientific Life Cycle Assessments (LCA) on face-masks to draw conclusions on which among the available alternatives, single-use or reusable, have the lowest environmental impacts, along their life cycle – from extraction of raw materials, to their end of life. The report finds that reusable masks (particularly if made from synthetic materials) are less damaging for the environment than single-use face masks, and reusable cotton masks, if used responsibly and economically. To identify which type of face masks are environmentally preferred; the study considers the following factors: • Number of reuses and washing practices (which are key to minimize environmental impacts); • Materials used; • Guidelines and standards on how to use masks; • Location of production vs. point of sale (transport); and • End-of-life disposal.