What does this sentence in a paragraph about the Notre Dame Fire mean?

Question

A 2017 Time article discussing the crumbling, wearing out, and water damage of France's Notre Dame Cathedral prior to the 2019 fire writes (emphasis added to the part I would like clarification on):

Notre Dame, which looms over the capital from an island in the center of the city, is a constant reminder of Paris’ history. It has seen more than its share of epic dramas, including the French Revolution and two world wars. But now there is another challenge. Some 854 years after construction began, one of Europe’s most visited sites, with about 12 million tourists a year, is in dire need of repairs. Centuries of weather have worn away at the stone. The fumes from decades of gridlock have only worsened the damage. “Pollution is the biggest culprit,” says Philippe Villeneuve, architect in chief of historic monuments in France. “We need to replace the ruined stones. We need to replace the joints with traditional materials. This is going to be extensive.”

Another SE user (smci on Skeptics) wrote:

The quote was ambiguous at best: "The fumes from decades of gridlock have only worsened the damage... “Pollution is the biggest culprit"' : culprit of what? of the fumes? (Clearly not "of the damage" since they only "worsened" it). Don't ask us to guess what the journalist was thinking. There's no point constructing an entire question around one sloppy journalistic sentence.

My interpretation is:

I assume that "The fumes from decades of gridlock have only worsened the damage." is a very simple sentence. It's a way to say that pollution has damaged the cathedral. I don't see why you interpret it as pollution is the culprit of the fumes. The fumes are polllution. As for worsened vs. damaged, the sentence is using "worsened the damage" as a synonym for "damaged."

1. Am I interpreting things correctly?

2. What is Villeneuve saying? (i.e. what does his quote mean?) Is the quote by Philippe Villeneuve saying that pollution is the biggest reason for the damage?

Answer 1

It is quite clear to me, that the quotation from Philippe Villeneuve adds to what has already been said, rather than being a cause of contradiction.

Pollution is the biggest culprit

is saying that besides the centuries of decay caused by weather and aging, the damage caused by pollution from traffic fumes has become the biggest factor in the degradation of the structure.

Answer 2

Sulfur in gasoline turns into sulfuric acid, which corroded limestone. I don't know if they still use leaded gasoline in France, but it turns things black, as do diesel particulates.