The answer to whether paper contains chemicals is yes. Paper is fundamentally a network of processed plant fibers and a variety of chemical compounds, both those naturally occurring in the wood source and those intentionally added during manufacturing. This material is created by breaking down raw fibrous material into a pulp, which is then reformed into thin sheets. The final product is a complex matrix where natural polymers are intertwined with substances introduced to achieve specific functional properties. The type and amount of chemicals present depend heavily on the paper’s intended use.
The Core Structure: Cellulose and Lignin
The structural foundation of almost all paper is a polymer known as cellulose, which is the most abundant organic compound on Earth. This long-chain carbohydrate is derived from plant cell walls. Its unique chemical structure allows the individual fibers to form strong hydrogen bonds when they are processed, wetted, and dried. These bonds create the cohesive, interwoven structure that gives paper its strength and flexibility.
Wood pulp, the primary source material, also naturally contains lignin, which acts as a glue holding the cellulose fibers together in the tree. Lignin is rich in aromatic rings, which absorb light and cause the paper to yellow and degrade when exposed to sunlight and air. Consequently, the pulping process is largely dedicated to chemically dissolving and separating this lignin from the desired cellulose fibers.
Manufacturing Additives for Functionality
Once the raw pulp is prepared, chemical additives are introduced to modify the paper’s physical and aesthetic qualities for its intended purpose. These functional ingredients transform the fiber sheet into a usable material. The goal is to control properties such as color, strength, water resistance, and printability.
Bleaching Agents
One of the first steps for many paper grades is the use of bleaching agents to remove residual lignin and increase the whiteness of the final product. Compounds like hydrogen peroxide, chlorine, or chlorine dioxide are employed to chemically alter or remove the light-absorbing structures left in the pulp. This process is crucial for papers where a bright white color is desired, such as writing paper or high-quality printing stock.
Sizing Agents
To make paper suitable for writing or printing with liquid inks, it must resist the penetration and spreading of water-based liquids. This resistance is achieved through the addition of sizing agents, such as rosin-based chemicals or synthetic compounds like alkyl ketene dimer (AKD) or alkenyl succinic anhydride (ASA). These chemicals repel water and prevent the ink from bleeding or soaking completely through the sheet, thereby ensuring crisp lines and clear images.
Mineral Fillers
Other chemicals are added not only for function but also to improve the paper’s appearance and reduce manufacturing costs. Mineral fillers, commonly including fine particles of calcium carbonate, clay, or titanium dioxide, are mixed into the pulp slurry. These substances fill the microscopic gaps between the cellulose fibers, which improves the paper’s smoothness, opacity, and brightness. By using these inorganic materials, manufacturers can also reduce the amount of more expensive wood fiber needed.
Specific Chemical Concerns in Specialized Papers
While standard office and printing papers rely on the chemicals discussed above, specialized paper products often incorporate additional compounds that have raised public health concerns. These chemicals achieve unique, high-performance characteristics not found in traditional paper. Two prominent examples are the chemicals used in thermal paper and those applied to grease-resistant food packaging.
Thermal Paper
Thermal paper, used for receipts, tickets, and labels, is coated with a mixture of chemicals that react to heat, allowing for inkless printing. This coating typically includes a color developer, which historically has been Bisphenol A (BPA). BPA is an endocrine-disrupting chemical that exists in a free, unbound form on the paper surface, making it easily transferable upon contact with skin.
Due to concerns over the dermal absorption of Bisphenol A, many manufacturers have replaced it with structurally similar compounds, most commonly Bisphenol S (BPS). However, BPS has also been shown to be an endocrine-active chemical that can transfer from the paper onto the hands of people who handle receipts. Studies have indicated that individuals who handle these thermal papers frequently show elevated levels of these chemicals in their bodies.
Grease-Resistant Packaging
Paper designed to resist grease and oil is often used for food wrappers, fast-food containers, and microwave popcorn bags. For decades, manufacturers have used Per- and Polyfluoroalkyl Substances (PFAS) as a grease-proofing agent because of their exceptional oil and water-repellency. These compounds are highly stable and resist breakdown, earning them the nickname “forever chemicals.”
Public health organizations have raised concerns about the migration of these chemicals from the packaging into food. While the use of PFAS provides a strong barrier against fat, the environmental persistence and potential for human bioaccumulation have led to regulatory changes. Manufacturers in the United States have recently completed a voluntary phase-out of substances containing PFAS used as grease-proofing agents for food-contact paper.