Limestone is a sedimentary rock composed mostly of calcium carbonate (CaCO3). It is a common building material because it is relatively soft and easy to carve, and it has a pleasing appearance. However, limestone is susceptible to damage from acid rain.

Acid rain is caused by the release of sulfur dioxide (SO2) and nitrogen oxides (NOx) into the atmosphere. These gases react with water vapor in the atmosphere to form sulfuric acid (H2SO4) and nitric acid (HNO3). These acids then fall to the ground in rain or snow, where they can damage buildings, plants, and animals.

Limestone is particularly vulnerable to damage from acid rain because it is a carbonate mineral. Carbonates react with acids to form carbon dioxide gas (CO2). This gas can cause the limestone to dissolve, which can lead to pitting, spalling, and other damage.

The environmental problems in New York that make limestone a poor choice to use on the outside of buildings include:

* High levels of sulfur dioxide and nitrogen oxides in the atmosphere: New York City is home to a large number of power plants and factories that release these gases into the atmosphere. This makes the city particularly susceptible to acid rain.

* Frequent rainfall: New York City receives an average of 43 inches of rain per year. This frequent rainfall can help to wash away the protective layer of limestone that forms on the surface of the stone.

* Harsh winters: New York City experiences harsh winters, with temperatures that can drop below freezing. This can cause the limestone to freeze and thaw, which can lead to cracking and spalling.

The combination of these environmental factors makes limestone a poor choice to use on the outside of buildings in New York City.