Impregnates – These substances have incredible properties – repel water and fat, protect against staining different materials. However, many studies have shown that the trace amounts found in our blood. Most preservatives are perfluorocarbons (PFCs), marked abbreviations PFOS and PFOA. Their molecules are extremely durable, so they can circulate in the environment for years. In animals can disrupt hormone levels and cause cancer. In humans, these substances can lead to thyroid disease and improve cholesterol levels.