The Chernobyl Nuclear Power Plant explosion remains the worst civilian nuclear disaster ever. The catastrophe blanketed much of western Russia and Europe beneath a toxic cloud, and even now, 30 years later, radiation appears in unusual places—like the migratory reindeer of Norway.

The reindeer live in southern and central Norway, where they graze on lichen and fungus—two things that ravenously absorbed the fallout of Chernobyl. As a result, many of the animals contain levels of radioactivity far beyond the European Union limit for consumption. That troubling for the Sami, an indigenous population that relies upon them for sustenance.

Photojournalist Amos Chapple spent a week in the village of Snåsa in January on assignment for Radio Free Europe1. He worked with a veterinarian and other experts to document how Sami herders live with the lingering effects of Chernobyl. Chapple, who photographed the coldest town on earth, braved single-digit temperatures during the project.

He and Grojec followed Sami herders as they corralled the reindeer and Norwegian scientists as they tested them. Some were vaccinated and released, including those with radiation levels too high for human consumption. Although researchers saw a spike in radiation in 2014, the animals Chapple photographed fell within Norway's limit.

In the days after Chernobyl, reindeer tested by the government ranged from 30,000 to 60,000 becquerel (a measure of radiation) per kilogram. That prompted authorities to increase the acceptable level from the EU cap of 600 becquerel per kilo to ensure the Sami could maintain their way of life. Today, the acceptable limit stands at 3,000.

"It is important to remember that the permissible levels are not 'toxic' limits," says Lavrans Skuterud, an environmental radiation expert with the Norway Radiation Protection Authority. Instead, the limits are meant to minimize the amount of irradiated food people consume, generally pegged at less than 75,000 to 80,000 becquerel annually.

Although the level of radiation has declined over time, periodic spikes occur. "The highest concentrations in reindeer during the last decade are mainly related to years when wild mushrooms are really abundant," says Skuterud. In September, 2014, researchers saw radiation levels as high as 8,200 becquerel per kilogram—up from 1,500 just two years before. The Sami released 900 reindeer to graze in less contaminated areas and delayed the slaughter for four months.

Skuterud says the maximum level recorded last year fell to 1,000 becquerel. Hugh Beach, a cultural anthropologist at Uppsala University, says herders started feeding the reindeer fodder in order to bring down radiation levels. He estimates that no more than a handful of slaughtered reindeer yield meat that later proves too radioactive to sell.

That doesn't mean the Sami aren't cautious, or mournful. "There’s a real sadness there," Chapple says, "because these people had always lived at one with nature, and suddenly in the days after Chernobyl, they woke up to their completely pristine landscape being one of the most contaminated places on the planet."

UPDATE: 3:34 EST 04/11/16: An earlier version of this story stated that Amos Chapple was accompanied by Wojtek Grojec. While Gorjec helped put the story together for the Radio Free Europe website, Chapple traveled alone.