Mushrooms near roads and cities: are they safe to pick?

You can know mushrooms inside out and take only young, firm specimens, yet still harm yourself if you pick them in the wrong place. Mushrooms near roads, factories and within city limits can be dangerous even when they belong to a perfectly edible species. The reason lies in how a mushroom is built.

Let's look at why the picking spot matters so much, how mushrooms accumulate harmful substances, and how far from roads and cities you can pick with peace of mind.

Why mushrooms soak up pollution

A mushroom is above all a huge mycelium in the soil, and the fruiting body we pick works like a sponge.

Threading through the ground with fine filaments, the mycelium absorbs water along with everything dissolved in it. If the soil contains heavy metals or toxic compounds, they end up in the mushroom too. Unlike plants, mushrooms are especially prone to accumulating such substances, and the fruiting body often holds more of them than the soil itself.

That's why even a beloved porcini that grew next to a highway can contain a dangerous dose of lead or cadmium, even though it looks no different from one from the forest.

Where the pollution comes from

Harmful substances build up most in a few typical places.

• Roadsides. For decades, exhaust fumes have been settling into roadside soil, leaving lead and other metals behind.
• Around factories and landfills. Industrial emissions and runoff saturate the ground with heavy metals and chemicals.
• City parks and squares. Here you get traffic emissions, chemical treatments and contaminated soil all at once.
• Fields after chemical treatment. Meadow mushrooms, such as the field mushroom, can absorb pesticides.

What these places have in common: the mushroom grows not in clean forest soil but in a polluted environment.

How far away is safe to pick

There's no exact boundary, but there are practical guidelines worth sticking to.

1. Move at least several hundred meters away from major highways. The deeper into the forest, the cleaner the soil.
2. Avoid the surroundings of factories and landfills. Don't pick here at all.
3. Don't pick in the city. Parks and squares, however green, are no place for a mushroom basket.
4. Avoid fields treated with chemicals. Meadow mushrooms from such places can't be trusted.

It's best to pick deep in clean forests, far from roads and human activity. That's where mushrooms such as honey fungus grow in clean soil.

Why it doesn't depend on the species

It's important to understand that the accumulation of pollutants has nothing to do with whether a mushroom is edible or not.

The most wholesome and tasty species, picked in a dirty place, becomes dangerous. And the other way around, the same care about where you pick is needed for all mushrooms without exception.

So choosing a clean forest is just as basic a rule as being able to recognize a mushroom. Together with the other guidelines, it's part of our safe foraging rules. And we look at the freshness and quality of the mushrooms themselves in the article on why you shouldn't take old and wormy mushrooms.

Sources

• "Vyznachnyk hrybiv Ukrainy" (Key to the Fungi of Ukraine; Kyiv, Naukova Dumka).
• Boletus edulis on GBIF, the global biodiversity database.
• Fungi on MycoBank, the international fungal nomenclature database.
• Bioaccumulation on Wikipedia.