Houses and apartments built or remodeled in the last decade tend to have one thing in common: The floors are usually covered in “luxury” vinyl plank, often in a sickly shade of gray. The material is cheap, and by scanning wood to make a print, manufacturers can somewhat convincingly mimic the real thing. But as the material gets more popular—it’s now the most common type of flooring in the U.S.—it’s also causing more problems.

The flooring is one example of a product that uses PVC, plastic made from vinyl chloride, the toxic chemical that burned in a plume of smoke over East Palestine, Ohio, earlier this month when a train derailed. Potential accidents are only one challenge. PVC products are dangerous to make, both for workers and communities nearby. They can potentially be dangerous to use because of additives. When they’re thrown out, that can lead to more pollution. And products like vinyl flooring keep growing, despite the fact that safer alternatives exist.

In China, where most vinyl flooring is now made, the first step usually involves making chlorine using mercury, another toxic chemical. The mercury “is released into the atmosphere and distributed globally,” says Jim Vallette, president of Material Research L3C, a company that studies PVC. “It comes out in the rain over the U.S. and the rest of the world.”

At Chinese factories that reportedly use forced labor, the chlorine gas is used to make vinyl chloride, a chemical known to cause cancer in workers repeatedly exposed to it. Making it also creates dioxins, other potent carcinogens, that then enter the environment and can build up in the food chain. (A single nanogram of one type of dioxin, or a billionth of a gram per liter of water, is unsafe for children, according to the EPA.) When the PVC is made, other additives are used to turn it into flooring; some Chinese factories use lead (also toxic) and phthalate plasticizers, another probable carcinogen that can also cause reproductive problems. Asbestos is also used in PVC production. And there are even more immediate dangers to workers’ health. In 2004, for example, a PVC plant in Illinois exploded, killing five people and forcing the community to evacuate. In 2018, a PVC plant in China exploded after a leak, killing 23 people and injuring 20 others.

The danger is highest for the people working at chemical plants or living nearby, though the accident in Ohio illustrates how anyone living along a transportation route for the chemicals could be affected. (Though most vinyl flooring is made in China, other PVC products, like pipes or windows, are still made in North America.) The Vinyl Institute, an industry trade group, touts the fact that its members have a higher safety record than average chemical producers in the U.S., though companies like OxyVinyls, which may have owned the polyvinyl chloride in the recent train accident, have a history of worker-safety issues.

And living with the final product isn’t necessarily risk-free. Perkins & Will, the architecture firm, noted in one report that some additives like plasticizers don’t bind tightly to PVC, so they can eventually end up in household dust that you breathe, or could be directly absorbed through bare feet. If PVC products burn in a fire, the chemicals in the smoke can cause permanent respiratory disease.

When PVC is eventually thrown out, if the products are burned in an incinerator, that also pollutes the air; in a landfill, the chemicals can leach into the environment (and landfills themselves can catch fire). Still, in January, the EPA denied a petition to classify PVC as a hazardous waste. Almost no PVC flooring is recycled, according to the nonprofit Center for Environmental Health, and most flooring manufacturers don’t want recycled PVC content in their products because it can add even more contaminants.

The issues with PVC aren’t new. A 2001 PBS documentary, Trade Secrets, outlined how chemical companies spent decades working to downplay the risk of disease for their workers. In 2015, the EPA finally passed a rule that limited some emissions from PVC plants. But it didn’t eliminate contaminants like dioxins. And when production is outsourced to countries like China, there’s more pollution.

It raises a question: Why are we still making products that are known to be unsafe, when alternatives exist and humans managed to live without it for centuries? Flooring, of course, isn’t the only product made with the material, though building products make up the majority of items made from PVC.

“I don’t know if you’ve been to a Lowe’s or Home Depot in recent years, but you can basically build a whole American home that looks like a Colonial Revival—columns, shutters, windows, siding—and the entire thing is plastic, is PVC,” says Jonsara Ruth, design director for the Healthy Materials Lab at Parsons School of Design.

In the case of vinyl flooring, the driving factor is cost; it’s cheaper than traditional hardwood floors. “It also looks like wood, but it doesn’t have the maintenance of wood,” says Ruth. “And so people are specifying it everywhere. It’s being used in hospitals, and schools, and in affordable housing, but also in high-end residential and hotels. It’s used across the board.” But some better alternatives exist, she says, including linoleum planks made to look like wood (natural linoleum is made from linseed oil from flax plants) or porcelain planks, which are made from clay.

Alternatives exist for other PVC products. Pipes can be made from cast iron, copper, or concrete. Window frames can be made from traditional wood instead of plastic. The rubbery backing on carpets can be made from safer plastics. Shower curtains can be made from fabric. Medical products like tubes and catheters can also be made from other materials. There are also alternatives for PVC packaging.

Some architecture firms, like Perkins & Will, have policies to urge their clients to avoid PVC. Ruth argues that in an ideal world, PVC products wouldn’t be made at all. But in the absence of regulation, designers can do more to move to safer materials.

“I think, as designers and architects, we have a huge agency in changing the course,” she says. “And builders [or] anybody in building or design. If we start demanding other products and kind of boycotting PVC plastics, then the manufacturers will follow, right? We talk to manufacturers all the time, and they say, ‘We’re just making what designers and architects want.’”