Other stories in brief
Are visitors at fault for Da Vinci deterioration?
LEONARDO da Vinci's
The Last Supperdraws many admirers, but could they be a source of pollution for the artwork? A new study from the US and Italy suggests that the air around the 15th-century mural in the refectory of Santa Maria delle Grazie Church in Milan harbours potential pollution from visitors.
“Although this painting has survived many challenges, including bombing during the second World War, it is yet facing another challenge,” write the authors in Environmental Science and Technology. “The painting, which was majorly restored in the 20th century, is at risk with air pollution arising from its surrounding Milan area. Milan is one of the most polluted areas in western Europe.”
A heating, ventilation, and air conditioning system was installed in recent years to help shield the painting from outdoor grime, and the researchers wanted to find out how well it was working.
For a year they monitored levels of fine and coarse particulate matter in the air, both outdoors and indoors, and the ventilation system came up trumps: it appears to be removing the bulk of pollution from the air coming in.
But there may be other potential sources of sullied air. The indoor sampling turned up relatively high concentrations of fatty acids, which could come from the skin of visitors.
If the lipids combine with dust in the air and come into contact with the painting they could contribute to soiling, according to lead author Nancy Daher, of the University of Southern California, in a statement.
The indoor-air samples also contained squalane, a compound that occurs naturally in humans and which is also used in skincare products.
Even the painting itself could be a suspect: the researchers describe how emissions from wax used in early restoration work could also be a source of pollution.
A link between full mouths and farming
IF YOU have ever endured the pressure and pain of overcrowded teeth, here’s a potential historic source of the problem: the switch to farming.
A new study suggests that the transition from the hunter-gatherer diet to agriculture resulted in the jaw growing too short and small relative to the size of the teeth it supports.
Dr Noreen von Cramon- Taubadel from the University of Kent at Canterbury looked at skull and jaw shapes in hunter-gatherer and agricultural populations, and found that diet seemed to have an impact on jaw development.
“Chewing behaviour appears to cause the lower jaw to develop differently in hunter-gatherer versus farming populations, and this holds true at a global level,” she says in an article on the university’s website.
Overall the hunter-gather groups had a longer and narrower lower jaw, while in the agriculturalists the lower jaw was generally shorter and broader, increasing the likelihood of dental crowding.
“The change from a hunter-gatherer economy to one based on animal and/or plant domesticates had a dramatic effect on the shape of the human mandible, effectively erasing the signature of past population history,” writes von Cramon-Taubade in the Proceedings of the National Academy of Sciences.
She concludes that the findings have “implications for our understanding of modern clinical phenomena, such as the relatively high incidence of dental crowding and malocclusions in postindustrial populations.”