Among all plastics, polyvinyl chloride (PVC) is the third-most produced by volume globally. In North America alone, more than seven million tons of PVC are produced each year. The basic building block of PVC is vinyl chloride, a chemical compound made of chlorine, carbon, and hydrogen. About three-quarters of all PVC manufactured is used in construction materials. It's used in piping, vinyl siding, vinyl flooring, and more. Yet despite its versatility, PVC is more hazardous than any other plastic over its life cycle—that is, from its production, through its use, to its eventual disposal.

Chemicals called organochlorines are added to produce PVC. The process for producing organochlorines requires a large volume of mercury, a pollutant known to cause severe reproductive, developmental, and neurological impacts at low doses. Dioxin, the most potent manmade cancer-causing agent ever tested in laboratory animals, is perhaps the best-known organochlorine. In living things, dioxin has been shown to harm development, reproduction, and both the immune and endocrine systems. Damage can result from even the smallest of doses—in the low parts per trillion.

Of the estimated seven billion pounds of PVC thrown away in the U.S. each year, less than one-half of one percent is recycled. The rest is put in landfills or incinerated. While trace amounts of dioxin may be released during PVC production, when burned, PVC releases significantly more dioxin into the environment. Dioxin is persistent, meaning it resists natural degradation. It also bioaccumulates, or builds up in the tissues of living things. As it moves through the food chain—through fish, other animals, and eventually to people—it accumulates at greater concentrations.

In its pure form, PVC is rigid and brittle. To make it flexible, as it's found in many consumer products, plasticizers are added. The main plasticizers used are a class of compounds called phthalates. Phthalates, which get mixed with the PVC polymer during formulation, have been found to damage the reproductive system of laboratory animals. They cause infertility, testicular damage, and reduced sperm count, and they suppress ovulation. Because they do not chemically bond to the plastic, they can leach out of—or escape from—the plastic over time, finding their way into the surrounding air and water.

With all the drawbacks of PVC, many organizations are now calling for use of alternative building materials that do not include organochlorines and do not pose the same hazards. For example, in place of vinyl siding, bricks and sustainably harvested or reclaimed wood are viable options. However, PVC has been regarded as a cheap wonder material for nearly 40 years, and many businesses or homeowners will not voluntarily choose to pay more for a PVC-free alternative.

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