Uncontrolled waste fires burn at much lower and inconsistent temperatures, which means combustion is incomplete. This releases substances from the waste and creates new ones as molecules are decomposed and reformed in the flames. Dioxins and related compounds are often formed when PVC is burned in open fires. At least 30 of these types of compound are considered harmful to human health. They can persist in the environment for years and in the human body for perhaps a decade or more. There is evidence they can damage the brain and disrupt hormones.
As rain falls on landfill sites, organic and inorganic constituents dissolve, forming highly toxic chemicals leaching into groundwater. Water that rinses through these chemicals collects at the base of the landfill and usually contains high levels of toxic metals, ammonia, toxic organic compounds and pathogens. This can result in serious contamination of the local groundwater. Even more dangers, this mixture usually creates a high biological oxygen demand, meaning it can quickly de-oxygenate water. If or when these noxious chemicals reach rivers or lakes, it could result in the death of aquatic life.