Pope Benedict on Sunday presided over a mass marking the feast of Pentecost during which he reflected on both spiritual and biological pollution saying, What air is for biological life, the Holy Spirit is for spiritual life; and just as an atmospheric pollution exists that poisons the environment and living organisms, there is also a pollution of the heart and the spirit that mortifies and poisons spiritual existence. He went on to say that the two images used to describe the importance of this feast are that of the storm and the fire. The Pope explained that the fire was the Holy Spirit which was brought to earth by Jesus.