Joshua Collins was driving through Kentucky when the hives broke out.

He didn’t know if it was something he ate, or an insect bite, but the itch was agonizing. An independent truck driver based at the time in California, he had a limited insurance policy with a high deductible. He called the emergency room of the closest hospital to see if it accepted his insurance. It didn’t.

“They were going to charge me an astronomical amount,” Collins said. “I ended up just waiting it out to see if it got worse. It lasted for a few weeks.”

Collins is one of 3.7 million heavy-duty truck drivers in the United States who work dangerous jobs and suffer disproportionate health problems, and yet are often underinsured. At the same time, they are driving vehicles that churn out climate-changing emissions, and their bosses are investing in technology that would seek to do away with human drivers altogether. At 25, Collins saw the intersection of those trends as a direct threat to his future.

That’s what led him to launch a long-shot primary challenge against Rep. Denny Heck (D-Wash.) in the Evergreen State’s 10th Congressional District, which stretches in a U-shape along the shoreline from Shelton through Olympia to Tacoma.