Working with the French Regional Centre for the Fight against Cancer and the Mexican National Institute of Public Health, in 1999 the company began a nine-month study in and around Mexico City - one of the most polluted cities in the world. To study the effects of ozone and nitric oxide on the skin, 96 people in a highly polluted district of the city were compared to 93 subjects living in a less exposed urban area 75 km away.
"We saw many differences between the two groups," explained Franois Christiaens of L'Oreal. "We observed increased oxidation of the sebum - the oily secretion that lubricates and protects skin and hair - and the very dry or very greasy skin features of our volunteers living in Mexico City."
Christiaens explained the consequences are cosmetic, as skin and hair smoothness and brightness change, and also more serious, as oxidation compromises the skin's natural defences and could also enhance irritation and allergic reactions.
Differences were sufficiently pronounced between people living less than a hundred kilometres apart that researchers grew interested in acquiring more precise information on regional air pollution levels. This in turn increased the existing interest in satellite data, already used for UV forecasting.
"Today UV doses are either collected from ground sites or come from models, but coverage is sparse and there are limited data over time," said Christiaens. "But satellite data can give us global maps of UV levels, and we can use them to work out realistic doses, as well as fine-tune the doses simulated in laboratory tests."