London - Air pollution produced by cars and lorries could be making men go bald, a study suggests.
Fine sooty "particulates" pumped out by vehicles are believed to destroy a protein that fuels hair growth.
In experiments, the particulates reduced levels of beta-catenin – which triggers skin cells to grow into hair. Three other proteins responsible for hair growth and retention were also reduced.
Study leader Dr Hyuk Chul Kwon said: "The results suggest particulate matter may cause hair loss." Male pattern baldness is hereditary but environmental factors are thought to make it worse.
Baldness affects two-thirds of all men at some stage in their lives.
The findings may shed light on rising rates of hair loss among younger men and could lead to a cream that targets the effects of pollution on follicles.
Dr Kwon said: "The link between air pollution and serious diseases such as cancer, chronic obstructive pulmonary disease and cardiovascular disease are well-established.
"But there is little to no research on the effect of particulate matter exposure on the human skin – and hair in particular."
His team took human scalp cells – "dermal papillae" – and exposed them to various concentrations of particulates.
It is known these chemicals, deposited into the atmosphere by transport and industry, increase the risk of illness. Dr Kwon said: "Our research explains the mode of action of air pollutants on... dermal papilla cells, showing how the most common air pollutants lead to hair loss".
Dermal papilla cells tell surrounding cells to generate hair follicles. Sources of particulate matter include the burning of fossil fuels such as petrol, diesel, coal, oil and "biomass" – plant and animal material. Others are industrial activities like building, mining and manufacturing cement, ceramics and bricks.
Dr Kwon, of the Future Science Research Centre in South Korea, added: "Ambient particulate matter represents an environmental threat to which millions of humans worldwide are exposed. The adverse effects on human health are currently a serious concern."
Hair loss can begin as early as the teens and by the age of 35 almost four in 10 men and women show some degree. The human head comes equipped with 100 000 tiny hair follicles, from each of which grows a single hair.
Recent research in China, the world’s most polluted country, found men in their 20s are going bald sooner than any generation before. Although balding is associated with advancing age, an increasing number of millennials in the US are experiencing hair loss.