A plasticizer is any compound that is added to plastics or other materials to make them softer, more flexible, or easier to process.
Plasticizers work by inserting themselves between the polymer chains, allowing those chains to slide past each other more easily and thereby reduce the materials rigidity. A polymer chain is a large molecule composed of many smaller molecules (called monomers), which are linked together in a repeating pattern, resembling a string of beads.
Total world production of plasticizers is currently roughly nine million metric tons, and is projected by industry sources to continue to grow at about four percent annually for the next ten or so years. As large as this seems, it is only about two percent of the approximately 450 million tons current annual production of plastics.
Plasticizers are used in a vast array of household, medical and industrial products. Examples of uses in household products include food packaging, shower curtains, toys, flooring, cosmetics, automobile interiors, table cloths and electronic products.
Slightly more than half of plasticizer output consists of phthalates, a group of colorless, organic compounds derived from petrochemicals. They are favored by plastics manufacturers because they are inexpensive, highly versatile, and effective at making plastics flexible, transparent and long-lasting.
The largest application for phthalates is as plasticizers for flexible polyvinyl chloride (PVC), which is used in a great variety of products, particularly in the construction and automotive sectors, but also in consumer products and medical devices.
The biggest category of non-phthalate plasticizers by production volume is adipates, which are likewise organic compounds derived from petrochemicals. They feature good low-temperature flexibility, compatibility with various polymers, and good cost-performance. Additionally, they are said to offer reduced toxicity and shorter biodegradation times as compared with phthalates. However, they are not entirely free from health and environmental risks, and the full extent of such risks is not yet known.
Plasticizers are harmful because they are not chemically bonded to the plastics and thus are easily released into the environment, because they persist after entering the soil and water and living organisms, and because of their toxicity.
For example, with regard to humans, the effects can include premature birth, infertility (especially in males), developmental disorders such as ADHD, and endocrine disruption. Also, they can enter fetuses during critical stages of development, possibly affecting hormone balance and long-term health. Relationships have also been found between plasticizer exposure and cardiovascular diseases, metabolic diseases such as obesity and diabetes, and reproductive problems.
The environmental and health effects of plasticizers and of microplastics are related but distinct issues. While those of plasticizers arise primarily from exposure to the chemical substances in them, microplastics are harmful both because they act as carriers for plasticizers and other toxic substances and because of physical hazards that they create within organisms.
Research continues on developing less toxic plasticizers, particularly those made from plant-derived materials, such as soybean oil, corn and sugar cane. Although substantial progress has been made, according to industry sources, they are generally still more costly than traditional petroleum-based plasticizers, due mostly to higher raw material costs and more complex production processes. Industry experts estimate that it will be at least a decade before such bio-based materials become the dominant form of plasticizers.
However, there is another serious concern with plant-derived plasticizers. It is the fact that producing them on the same scale as that currently for fossil-fuel derived plasticizers would require vast amounts of energy, fresh water and arable land, thereby competing with food crops and thus driving up the prices of food. The substantial energy requirement includes that for fertilizer production, irrigation, and machinery use.
The growing menace of plasticizers in the environment and human body is just one of multiple environmental and health consequences of the current massive and ever-growing level of plastics production and consumption. This is yet another reason that, as difficult as it might seem, the best solution might be to begin to reduce the production of plastics instead of continuously increasing it.