Air pollution causes skin darkening

In this study, funded partly by companies marketing skincare products, researchers in Germany investigated this in human skin. The authors used both ‘ex vivo’ and ‘in vivo’ experiments. In ex vivo studies tissue is taken from a living organism, in this case people having operations, and then studied in a laboratory. In contrast, in in vivo studies the experiments are actually carried out in the living organism, in this case healthy volunteers. First they studied skin ex vivo in controlled experiments using unwanted skin from ‘tummy tuck’ operations. Samples treated with solutions of diesel exhaust particles (DEP) over several days became progressively darker, because of increased melanin that in turn was caused by increased expression of genes responsible for melanin production...