Explanation

Mathura based petroleum refinery is poisoning threat to Taj Mahal in Agra and other monuments at Fatehpur Sikri complex. Petroleum or oil refineries are the major source of gaseous pollutants and the gases released from these are $SO_{2}$ and $NO_{x}.\ NO_{x}\ and\ SO_{2}\$get mixed with atmospheric moisture and form $HNO_{3},\ H_{2}SO_{4}$, etc, which react with marble and cause corrosion.