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How poor air quality in Hong Kong is damaging your skin – and the cancer risks to watch for

Traffic-related air pollution can cause dark spots, known as lentigines or “liver spots”, on the skin of Asian women over the age of 50, some forms of which may be pre-cancerous, say researchers
Air pollution caused by traffic can do more than just wreak havoc on your respiratory system – it may also cause the formation of dark spots on the skin, according to a new study by German and Chinese researchers.

These dark spots, also known as lentigines, were most obvious on the cheeks of Asian women over the age of 50, say the researchers, writing in the Journal of Investigative Dermatology.

The study involved about 1,550 women, roughly half of whom were German and the other half Han Chinese from the Taizhou region in Jiangsu province.

Lentigines, also known as liver spots, are small, darkened areas of the skin. Although they may first appear small, they may enlarge and separate patches may merge. They are most commonly found on the face, forearms, hands, and upper trunk. Usually brown, lentigines can appear yellow-tan to black. They are generally benign, although some may be pre-cancerous.

“In addition to particulate matter, traffic-related air pollution is characterised by increased concentrations of nitrogen dioxide (NO2). While NO2 exposure is known to be associated with low lung function and lung cancer, its effect on human skin has never been investigated. This is important because environmentally induced lung and skin ageing appear to be closely related,” says lead investigator Dr Jean Krutmann of the IUF-Leibniz Research Institute for Environmental Medicine in Dusseldorf.

The 806 German women had an average age of 73½ years (range 67 to 80 years) and 20 per cent had a history of smoking. These women reportedly spent an average of just over 2½ hours a day in the sun. Their average level of NO2 exposure was 28.8 micrograms per cubic metre.

The 743 Chinese women had 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 3½ hours. Their average level of NO2 exposure was 24.1 micrograms/m3.

Overall, an increase of 10 micrograms/m3 in NO2 concentration was associated with approximately 25 per cent more dark spots. No association was seen between levels of NO2 and lentigines’ formation on the back of the hands or forearms. However, exposure to NO2 was significantly associated with more lentigines on the cheeks in German and Chinese women older than 50 years.

The average NO2 level in Hong Kong in 2015 was 98 micrograms/m3 (roadside air pollution) according to figures from the Environmental Protection Department.

The researchers performed sensitivity analysis and found that NO2 gas had a slightly greater impact on dark spot formation than the particulate matter concentration.

“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,” notes co-investigator Li Jin of Fudan University’s State Key Laboratory of Genetic Engineering and the Fudan-Taizhou Institute of Health Sciences in Jiangsu, China. “The findings also strengthen the concept that the pathogenesis of lentigines might differ depending on the anatomical site.”

The effects of air pollution can persist for more than three decades after exposure, a separate new study by researchers at Imperial College London has found.

The researchers followed 368,000 people in England and Wales over a 38-year period and estimated air pollution levels in the areas where the individuals lived in 1971, 1981, 1991 and 2001, using measurements from Britain’s extensive historic air pollution monitoring networks.

Highest risks were seen for respiratory disease, such as bronchitis, emphysema and pneumonia, as well as mortality risk from cardiovascular disorders, such as heart disease.

The study found that for every additional unit of pollution (equivalent to 10 micrograms/m3) that people were exposed to in 1971, the risk of mortality in 2002 to 2009 increased by two per cent.

The researchers also looked at more recent exposure and found a 24 per cent increase in mortality risk in 2002 to 2009 for each additional unit of pollution people were exposed to in 2001.

“Our study found more recent exposures were more important for mortality risk than historic exposures, but we need to do more work on how air pollution affects health over a person’s entire lifetime,” says Dr Anna Hansell, lead author of the study published in the journal Thorax. “We were surprised to find pollution has effects on mortality that persist over three decades after exposure.”

Hansell, however, adds that it’s important to remember that the effects of air pollution are small compared to other risk factors like whether you smoke, how much you exercise, whether you are overweight, as well as medical factors such as your blood pressure.

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