There might be a link between traffic-related air pollution and the formation of facial lentigines, according to results of a study involving a cohort of women from Germany and China.
“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,” said Dr. Jean Krutmann, lead investigator of the study published in the Journal of Investigative Dermatology (May 2016; 136(5):1053–1056), who was quoted in a press release.
This research is important because environmentally-induced lung and skin aging appear to be closely related, said Dr. Krutmann, professor at the IUF-Leibniz Research Institute for Environmental Medicine in Dusseldorf, Germany.
During the investigation, the researchers studied two groups:
The first group included 806 Caucasian German women who were part of the SALIA study (Study on the influence of Air pollution on Lung function, Inflammation and Aging). Average age was 73.5 years (range 67 to 80 years) and 20% had a history of smoking. These women reportedly spent an average of 2.6 hours per day in the sun.
The second group involved 743 Asian women from the Taizhou region in China, who were somewhat younger than the SALIA group, with an average age of 59 (range 28 to 70 years). Twenty per cent of this group had a history of smoking, with a reported average daily sun exposure of 3.5 hours.
Data revealed that many more women in the SALIA group reported using cosmetics with sun protection (61% vs. 4.2%). The findings also showed that the mean levels of NO2 exposure were 28.8 µg/m3 in the SALIA study and 24.1 µg/m3 in the Taizhou, China group.
Overall, the authors reported that no association was seen between levels of NO2 and formation of lentigines on the back of the hands or forearms; however, exposure to NO2 was significantly associated with more lentigines on the cheeks in both German and Chinese women older than 50 years of age.
The researchers also reported that an increase of 10 µg/m3 in NO2 concentration was found to be associated with approximately 25% more lentigines.
The investigators also performed sensitivity analysis to see whether they could pinpoint whether the concentration of particulate matter or NO2 gas had a greater impact on lentigines formation. They found that the NO2 gas had a slightly stronger effect than the concentration of particulate matter.
“To the best of our knowledge, this is the largest epidemiological study demonstrating a link between traffic-related air pollution and the formation of lentigines,” noted co-investigator Li Jin, PhD, of Fudan University’s State Key Laboratory of Genetic Engineering and Ministry of Education Key Laboratory of Contemporary Anthropology, Collaborative Innovation Center for Genetics and Development, School of Life Sciences in Shanghai, China.
“The findings also strengthen the concept that the pathogenesis of lentigines might differ depending on the anatomical site,” concluded Dr. Jin.