Polylactic acid (PLA) is a widely used bioplastic, often assumed non-toxic due to its environmental benefits and presence in everyday products. While generally considered safe, understanding its composition, degradation, and practical applications provides a complete picture. This article explores the scientific basis of PLA’s safety and influencing factors.
What is PLA?
Polylactic acid (PLA) is a plastic derived from renewable sources like corn starch, sugarcane, or cassava. Unlike traditional fossil fuel-based plastics, PLA is a bio-based polymer. Its fundamental building block is lactic acid, which polymerizes to form the plastic’s long chains.
PLA’s low melting point and ease of processing make it suitable for various applications. It is widely used as a 3D printing filament, in food packaging, and for disposable tableware.
The Science Behind PLA’s General Safety
PLA is considered non-toxic due to its inherent biocompatibility. The lactic acid monomer, its building block, is naturally present in the human body. This contributes to PLA’s favorable interaction with biological systems.
Under normal conditions, PLA remains largely inert, not readily reacting or releasing harmful compounds. This leads to its extensive use in medical applications, such as dissolvable stitches, orthopedic devices, and drug delivery systems. These applications demonstrate its safe degradation within the body.
PLA’s biodegradability also contributes to its safety. In controlled environments like industrial composting facilities, PLA degrades into water, carbon dioxide, and biomass. The body metabolizes or excretes the lactic acid produced during degradation.
Factors Modifying PLA’s Safety Profile
While pure PLA is generally safe, its safety profile can be influenced by manufacturing additives. Colorants, plasticizers, and fillers are often incorporated to modify properties like flexibility or appearance. Some additives may introduce substances less benign than PLA, potentially affecting safety for food contact or medical applications.
The conditions under which PLA is used or degrades can also modify its safety. Although PLA is designed to degrade into simple, harmless compounds, this process is typically optimized for specific conditions like industrial composting. Under harsh or uncontrolled conditions, such as prolonged exposure to high temperatures or certain chemical environments, the degradation process might yield different byproducts. This can be a concern if PLA products are subjected to conditions beyond their intended use.
Concerns also arise regarding emissions during processes like 3D printing. When PLA filament is heated during 3D printing, it can release ultrafine particles (UFPs) and volatile organic compounds (VOCs). While PLA is often noted for having lower emissions compared to other filaments like ABS, these airborne particles and compounds can still be irritants. Adequate ventilation is important when 3D printing with PLA to minimize exposure to these emissions, especially for individuals with respiratory sensitivities.
Navigating Safe Use and Practical Considerations
Safe use of PLA requires understanding specific grades and applications. For products intended for food contact, such as packaging or disposable cutlery, certain grades of PLA have received regulatory approval. In the United States, the Food and Drug Administration (FDA) has recognized specific PLA polymers as Generally Recognized as Safe (GRAS) for use in food-contact articles under defined conditions. Similarly, the European Union has regulations that govern plastic materials intended to come into contact with food, setting migration limits for substances. These approvals apply to the pure PLA polymer itself and specific formulations, not necessarily to every PLA product, particularly those with added colorants or other non-food-safe components.
Practical considerations for consumers using PLA products include avoiding extreme heat exposure. PLA has a low glass transition temperature, meaning it can soften or deform when exposed to hot liquids or high temperatures, such as in a dishwasher. For 3D printing with PLA, ensuring the printing area is well-ventilated helps to disperse any emitted ultrafine particles and volatile organic compounds. While PLA is broadly considered safe, individual sensitivities can vary, and awareness of a product’s specific formulation and intended use is beneficial for leveraging PLA’s advantages responsibly.