Statues and monuments in India are affected by acid rain.

Acid rain is a byproduct of various human activities that leads to the emission of oxides of sulphur and nitrogen in the atmosphere. These oxides undergo oxidation and then react with water vapour to form acids.

$2 \mathrm{SO}_{2(g)}+\mathrm{O}_{2(g)}+2 \mathrm{H}_{2} \mathrm{O}_{(t)} \longrightarrow 2 \mathrm{H}_{2} \mathrm{SO}_{4(a q)}$

$4 \mathrm{NO}_{2(g)}+\mathrm{O}_{2(g)}+2 \mathrm{H}_{2} \mathrm{O}_{(t)} \longrightarrow 4 \mathrm{HNO}_{3(a q)}$

Acid rain causes damage to buildings and structures made of stone and metal. In India, limestone is a major stone used in the construction of various monuments and statues, including the Taj Mahal.

Acid rain reacts with limestone as:

$\mathrm{CaCO}_{3}+\mathrm{H}_{2} \mathrm{SO}_{4} \longrightarrow \mathrm{CaSO}_{4}+\mathrm{H}_{2} \mathrm{O}+\mathrm{CO}_{2}$

This results in the loss of lustre and colour of monuments, leading to their disfiguration.