NEW DELHI — For the first time ever, the Taj Mahal, India’s monument to eternal love, is getting a serious cleaning.

For more than 350 years, monsoon rains in Agra, the bustling city where the monument sits, were enough to wash dirt off the structure’s walls. But pollution has worsened over the last couple of decades, and parts of the marble facade have turned yellow and black.

Since 2015, workers have scaled the monument’s minarets and walls to correct discoloration and remove layers of grime from the 17th-century structure, which was built by the Muslim emperor Shah Jahan as a mausoleum for his favorite wife, Mumtaz Mahal.

Behind the monument, the Yamuna River has also filled with sewage and other waste, worsening the problem by attracting millions of mosquito-like insects. They settle near the backside of the Taj Mahal and excrete a green substance on its walls during mating flights.