Cleaner air surrounds 'Last Supper'

MILAN, Italy, Nov. 23 (UPI) -- Efforts to protect Leonardo Da Vinci's "Last Supper" from air pollution appear to be succeeding, University of Southern California researchers said.

The refectory of Santa Maria Delle Grazie Church in Milan installed a sophisticated heating, ventilation and air conditioning system in 2009 to protect the painting from the polluted air of Milan. Italian officials hired Constantinos Sioutas, a professor of civil and environmental engineering at the USC Viterbi School of Engineering, to test the effectiveness of the protection efforts.

The findings, which will be presented next month in Milan, show the church is winning the war with outdoor air pollution, Sioutas said Wednesday in a release. Fine and coarse particulate matter concentrations were reduced around the painting by 88 and 94 percent, respectively. Visitors, however, remain a potential risk to the painting.

Nancy Daher, lead author of an article published in Environmental Science and Technology, said fatty lipids from the skin of visitors to the church still appeared in significant quantities around the painting -- even though visitor access to the painting is strictly regulated.

Airborne lipids from visitors' skin can combine with dust in the air and, if they come in contact with the painting, soil it, Daher said.