The controversy over drivers getting inappropriately classified as independent contractors usually focuses on Uber and Lyft , the ride-hailing companies who are under increasing pressure to change the way their workforce is compensated. With the current contractor setup, these companies can foist costs usually paid by large companies—like healthcare, gas, or car repairs—onto individual drivers.

But as California’s legislature considers Assembly Bill 5, which would reclassify independent contractors as employees if they meet certain criteria, there’s another, less publicized type of driver misclassification problem the state is also trying to tackle: independent contract truckers. AB5 would make it so truck drivers who currently work as independent contractors could become full employees of their companies, so long as they work exclusively at the control of those companies and don’t independently operate their own businesses (as many contract truckers currently do not). This change would not only give deserving truck drivers much-needed employee benefits but could also dramatically cut emissions in the state.

Forty percent of all greenhouse gas emissions in California come from motor vehicles, and a fifth of that comes from “heavy-duty” vehicles, like trucks. Diesel-fueled trucks cause a particularly lethal type of pollution, emitting particulate matter that, according to the California Air Resources Board, is responsible for 70% of airborne toxics-based cancer risk.

Worsening this problem is the trucking industry’s insistence on misclassifying drivers as independent contractors, says a new report from the UC Berkeley Labor Center, written by Sam Appel and Carol Zabin. But what do labor practices have to do with toxic emissions?

“Imagine you’re an independent contractor truck driver, and you’ve been engaged by your employer to lease your own truck,” says Appel, a labor, climate, and racial justice organizer with the BlueGreen Alliance. “You’re earning somewhere between $28,000 and $35,000 a year, and you have to pay your own payroll and employment taxes.” Meanwhile, California has passed and is working on implementing new policies aimed at getting the trucking industry to adopt low-emission and zero-emission vehicles. Implementing these policies is costly, and trucking companies often inappropriately shift the financial burden to low-wage-earning contractors, who can’t afford to update their trucks or get new ones. (The same goes for Uber and Lyft drivers, who, as contractors, would be forced to pay for emission-cutting upgrades, like by renting or buying their own efficient cars.)

The trucking industry has long been a focal point for both environmental and labor advocates in California, “for at least the last 10 to 15 years,” says Appel. In 2008, the state passed the Truck and Bus Rule, which requires truck owners and renters to start using trucks with more efficient engines or diesel particulate filters by specific dates; most trucks will be required to update by the start of 2023. Truckers that fail to do this are considered out-of-compliance.

“The dirtiest trucks in the state [are] driven by a largely immigrant workforce that is highly exploited,” says Appel. These aren’t the people who can afford to pay more than $200,000 for a zero-emission electric truck, the projected cost of such a vehicle in 2024.