Chewing on objects like pen caps, plastic straws, or the edges of water bottles is a common habit rooted in stress relief or oral fixation. While it may seem harmless, repeatedly putting these non-food items into the mouth is a direct route for potentially harmful substances to enter the body. The concern stems from a combination of chemical additives within the plastic material and the physical breakdown of the material itself. Understanding the components of everyday plastics and how the act of chewing affects them reveals the potential health issues associated with this widespread behavior.
Chemical Leaching and Exposure Risks
The primary health risk from chewing plastic comes from the migration of non-polymeric chemicals, which are additives mixed into the plastic to enhance its properties. Mechanical stress from chewing, combined with the presence of saliva and the warmth of the mouth, accelerates the release of these compounds from the plastic matrix. This process, known as leaching, exposes the body to substances that were never intended for ingestion.
Plasticizers, such as phthalates, are a significant concern because they are used to make hard plastics like polyvinyl chloride (PVC, resin code 3) more flexible and durable. These chemicals are not chemically bound to the plastic polymer, allowing them to migrate relatively easily upon contact and abrasion. Similarly, Bisphenol A (BPA) is a monomer used in the production of polycarbonate plastics (resin code 7) and epoxy resins, which can also leach out, particularly when the material is stressed or damaged.
Certain plastics, especially those marked with resin codes 3 (PVC), 6 (Polystyrene), and 7 (Other, often including polycarbonates), are associated with a higher potential for containing high-risk additives. Beyond plasticizers and monomers, some colorants and heat stabilizers contain heavy metals like lead, cadmium, or antimony. Continuous abrasion from chewing can facilitate the release of these metals, even though they are often tightly bound within the polymer structure. The cumulative effect of low-dose exposure to these migrating chemicals is that they are absorbed through the mucous membranes in the mouth.
Health Effects of Ingested Plastic Components
Once absorbed, many of the leached chemicals are classified as endocrine-disrupting chemicals (EDCs) because they interfere with the body’s hormonal system. EDCs like BPA can mimic the natural hormone estrogen, binding to hormone receptors and potentially altering normal biological signaling. Phthalates, such as Di(2-ethylhexyl) phthalate (DEHP) and Dibutyl phthalate (DBP), are known to exhibit anti-androgenic effects, meaning they can block the action of male hormones like testosterone.
This hormonal interference is linked to a range of potential health consequences, even at very low exposure levels. Endocrine disruption can affect the reproductive system, with studies associating exposure to these compounds with reduced sperm quality and count in males and conditions like Polycystic Ovary Syndrome (PCOS) in females. The compounds may also influence metabolic processes in the body.
Exposure to plastic-associated chemicals has been linked to an increased risk of developing conditions such as obesity and type 2 diabetes. The body’s detoxification organs, like the liver, must process these foreign compounds, potentially leading to increased liver stress over time. Sustained exposure can also contribute to immune system alterations, though the long-term systemic effects of this chemical exposure are under investigation.
Physical Damage and Microplastic Concerns
Beyond the chemical risks, the physical act of chewing on hard plastic objects presents direct hazards to oral health. Repeatedly biting down on materials like pen casings or hard straw pieces can cause microfractures in tooth enamel, leading to increased sensitivity and wear. Over time, this abrasive action can contribute to enamel erosion and may even cause teeth to chip or crack, requiring expensive dental restoration.
The constant tension and pressure exerted on the jaw from chronic chewing can also strain the temporomandibular joint (TMJ), potentially causing pain and discomfort in the jaw, face, and neck. As the plastic object is repeatedly chewed, small fragments of the material inevitably break off and are swallowed. These tiny pieces, known as microplastics, pass through the digestive system.
Microplastics are largely inert and pass out of the body, but their presence is concerning for two reasons. They can cause minor digestive irritation as they travel through the gastrointestinal tract, especially when consumed regularly. Furthermore, microplastics can act as carriers, adsorbing and transporting other contaminants into the body.
Strategies for Reducing Plastic Exposure
For individuals who habitually chew on plastic, the most effective strategy is to identify common culprits, such as disposable straws and pen caps, and replace them with safer alternatives. Many people chew to manage stress, anxiety, or satisfy a sensory need, meaning the habit requires a suitable substitute. Switching to pens with metal casings or using reusable, chew-resistant straws made of silicone or stainless steel can eliminate the immediate source of exposure.
Specialized sensory chew tools, often made from non-toxic, food-grade silicone, are designed for adults and provide a safer outlet for oral fixation. These alternatives are engineered not to leach chemicals and are durable enough to resist physical breakdown. Addressing the underlying behavioral cause is equally important, so incorporating stress-reduction techniques or using alternatives like chewing gum or mints can help redirect the urge.