Study links air pollution to dark spots on the face

The research, published in the Journal of Investigative Dermatology​​,  studied a group of Caucasian German women and a group of Han Chinese women, finding link between levels of traffic-related air pollution and air pollution-associated gases with the formation of lentigenes on the skin.

"To the best of our knowledge, this is the largest epidemiological study demonstrating a link between traffic-related air pollution and the formation of lentigenes,"​ says co-investigator Dr Li Jin, vice president of Fudan University.

"The findings also strengthen the concept that the pathogenesis of lentigenes might differ depending on the anatomical site."​

Lead investigator Dr Jean Krutmann of the IUF-Leibniz Research Institute for Environmental Medicine, explains that in addition to particulate matter, traffic-related air pollution is characterized by increased concentration of nitrogen dioxide (NO2).

“While NO2 exposure is known to be associated with low lung function and lung cancer, the effect of NO2 on human skin has never been investigated,”​ says Krutmann.

“This is important because environmentally-induced lung and skin ageing appear to be closely related." ​

Research​

In the study, a group of 806 Caucasian German women ranging from ages 67 to 80, and a group of 743 Han Chinese women from the Taizhou region aged 28-70 were observed; with the mean levels of NO2 exposure recorded at 28.8 µg/m3 in the German group and 24.1 µg/m3 in the Chinese group.

The scientists noted that no association was seen between levels of NO2 and lentigenes' formation on the back of the hands or forearms; however, exposure to NO2 was significantly associated with more lentigenes on the cheeks in both German and Chinese women older than 50 years.

Overall, an increase of 10 µg/m3 in NO2 concentration was associated with approximately 25% more dark spots.

The most pronounced changes were observed on the cheeks of Asian women over the age of 50.

The spots were visually evaluated by trained personnel according to photo reference scales and quantified using a validated skin aging score system (SCINEXA).

The investigators performed sensitivity analysis to see whether they could pinpoint whether it was the concentration of particulate matter or NO2 gas that had a greater impact on dark spot formation, and found that the NO2 gas had a slightly stronger effect than the particulate matter concentration.