State of the Planet: Lead Fallout From Notre Dame Fire Was Likely Overlooked

This article was published by Sarah Fecht on the Earth Institute's blog, State of the Planet.

July 10, 2020

On April 15, 2019, the world watched helplessly as black and yellow smoke billowed from the Notre Dame cathedral in Paris. The fire started just below the cathedral’s roof and spire, which were covered in 460 tons of lead — a neurotoxic metal, dangerous especially to children, and the source of the yellow smoke that rose from the fire for hours. The cathedral is being restored, but questions have remained about how much lead the fire emitted into the surrounding neighborhoods, and how much of a threat it posed to the health of people living nearby.

A new study, published today in GeoHealth, used soil samples collected from neighborhoods around the cathedral to estimate local amounts of lead fallout from the fire. Lead levels in the soil samples indicated that nearly a ton of lead dust dropped down within one kilometer (0.6 miles) of the site, and areas downwind of the fire had double the lead levels than sites that were outside the path of the smoke plume. The study concludes that, for a brief time, people residing within a kilometer and downwind of the fire were probably more exposed to lead fallout than measurements by French authorities indicated.

Early evidence suggested that the fire increased lead exposure in Paris. Air quality measurements taken 50 kilometers away from the cathedral found that lead particulates in the air were 20 times higher than usual in the week after the fire. However, a small set of measurements by France’s Regional Health Agency, posted weeks after the fire, found that all the samples collected outside of the out-of-bounds area around the cathedral had lead levels below France’s limit of 300 milligrams per kilogram of soil. At the time, there were fears that the health agency was underplaying the potential health impacts and not being transparent enough.

“There was a controversy — were children being exposed or not from this fallout?” said Lex van Geen, a geochemist at Columbia University’s Lamont-Doherty Earth Observatory and lead author on the new study. “So I thought, whether I get a ‘yes’ or a ‘no,’ it’s worth documenting.”

In December 2019 and February 2020, van Geen collected 100 soil samples from tree pits, parks and other locations around the cathedral, and in particular to the northwest, where most of the smoke traveled on the day of the fire. When lead enters soil, it tends to stay put, so it can preserve the signal of the fallout for much longer than hard surfaces such as roads and sidewalks, which get swept and flushed by rain.

“It wasn’t a particularly glamorous expedition,” said van Geen. “I got plenty of strange looks from people wondering why this old guy was scooping up soil, trying to avoid the dog poop, and putting some of the soil in paper bags. But it got done.”