https://www.nhpr.org/environment/2022-08-19/outside-inbox-i-found-coal-in-my-garden-are-my-vegetables-safe-to-eat

 A handful of coal unearthed from the garden.

Every other week on NHPR's Morning Edition, the Outside/In team answers a listener question about the natural world.

This week’s question comes from Maureen McMurray, in Concord, New Hampshire. Full disclosure: Maureen used to work on Outside/In, but these days she's just a listener.

For the past few years, Maureen’s been growing vegetables in a backyard garden. Sometimes, she finds chunks of coal in the soil when she’s digging.

“I’m growing stuff that’s in the same soil as all of this coal… am I poisoning myself and my family?”

This story is adapted from Yardwork, a summer yard and garden series from Outside/In. To listen to a longer version of this story, click here.

Maureen’s house was built in 1880, so these coal chunks could be leftover from the days when most of the houses in the city were heated with coal.

“My first reaction is that I think it's probably a fairly common issue,” said Nate Bernitz, public engagement program manager at the University of New Hampshire (UNH) Cooperative Extension.

Mysterious coal chunks notwithstanding, Nate said that getting your home garden soil tested is always a great idea.

“There's kind of a thought that food is safer when you grow it yourself, which may or may not be true,” said Nate.

Nate recommended testing the soil for heavy metals, which can be associated with coal ash.

The term "heavy metal" is a bit of a loose one, but generally, heavy metals are a class of elements which are toxic even in tiny amounts. Exposure can cause cancer, organ failure, or impact brain development.

Since this is an old house in an old city, one of the biggest to watch out for is lead. Lead is the most common urban soil contaminant because of its historical use in lead paint and leaded gasoline. The latter wasn’t fully banned for passenger cars until 1996.

The method to sample your soil is pretty simple: dig up a few samples from six inches deep from around the garden, mix and air-dry the soil, pour it into a labeled, plastic sandwich bag, and mail everything off to the lab.

The standard home and garden test costs $20, but we added a couple extra tests, including heavy metals, so our lab fee totaled $152. When the lab emailed the results a few weeks later, the report showed that heavy metals were present.

 A ziplock bag containing the soil sample.