Why is acid rain considered a threat to Taj Mahal ?

Explanation

Taj mahal is made of marble . The acid rain contains `H_(2)SO_(4)` which attacks the marble `(CaCO_(3))` thereby pitting it, decolourising it and making it lustreless.
`CaCO_(3)+ H_(2)SO_(4) to CaSO_(4) +CO_(2)+H_(2)O`