Human skin serves a protective purpose and its outermost layer serves as a shield against pro-oxidative chemicals and physical air pollutants. Exposure to ambient air pollution causes numerous adverse effects, including extrinsic aging (from exposure to UV radiation over time), psoriasis, dermatitis and eczema; additionally penetration of oxidative compounds through skin pores leads to dyspigmentation and exposure to cigarettes leads to an increased incidence of skin cancer.
This article presents the results of a systematic review on the effects of different forms of air pollution on skin colour and pigmentation, with particular reference to intrinsically and extrinsically aged skin, while outlining key molecular mechanisms responsible for producing observed phenotypes.
Studies employ various methodologies for quantifying skin ageing, but distinguishing between constitutive and facultative pigmentation is sometimes challenging. Furthermore, several variables influence pigmentation: ethnicity (Europeans have lighter skin while Africans have darker), sun exposure and skin phototype. All these variables make comparison between studies challenging.
Skin aging manifestations are generally assessed visually, which can be subjective and dependent on cultural perceptions of old. This limits the accuracy of outcome measures produced from individual studies, making comparison between methodologies difficult. Researchers have discovered more objective means of measuring phenotypes through skin conductance measurement with Skicon-200 and biopsy staining with Glyoxalase 2. In this study directly measured PM2.5 exposure in 30 households and divided participants into high and low exposure groups according to annual mean concentration; wrinkles and laxity evaluation, size of pigment spots and lentigines were evaluated for both groups.