Pollution as a risk factor for the development of melasma and other skin disorders of facial hyperpigmentation ‑ is there a case to be made?

Worldwide air pollution is a major health concern. There is accumulating scientific evidence that air pollution plays an important role in extrinsic aging. This article invites the reader to consider pollution as a possible emerging etiologic agent for the development of melasma. Pollution may be a risk factor for melasma and other facial pigmentary dyschromias. Air pollution in the form of airborne particulate matter (PM) and Polycyclic aromatic hydrocarbons (PAHs) enter the skin via nanoparticles and generate quinones, which are redox-cycling chemicals that produce reactive oxygen species (ROS). The PM increases the amount of ROS that triggers the increase of metalloproteinases that leads to extrinsic aging, which includes skin pigmentation. The incidence of disorders of facial hyperpigmentation specifically, melasma, is increased in persons of skin type III-VI living in India and South East Asia. Interestingly, these are also geographic regions with very heavy pollution. India, South East Asia, China, and United States lead the world in air pollution.