The plastics enterprise depends on a small number of commodity polymers to perform in diverse applications, requiring additives to produce desired properties and performance. Toxic effects and environmental persistence of certain additive chemicals impact the sustainability of the industry. Green chemistry has been and will continue to be applied to find solutions to these issues. This review focuses on alternatives to phthalate plasticizers and halogenated flame retardants, two categories that together account for a significant portion of the global additives market and the global dispersion of endocrine-disrupting chemicals. Small-molecule alternatives that exist in various stages of research and commercialization will be discussed, with emphasis on the use of renewable resources. The rise of biorefineries and new bio-based monomers may help overcome existing economic barriers to adoption of alternatives. Increasing the molecular weight of additives or covalently linking them to polymer backbones are two promising strategies for reducing both mobility and toxicity that will also be discussed. Finally, the design of new polymers that show desirable properties without the use of additives will be considered. The substances put forward as "green" alternatives have yet to receive the same level of scrutiny as diethylhexyl phthalate (DEHP, also known as dioctyl phthalate) or polybrominated diphenyl ethers (PBDEs). Cooperation between chemists, engineers, and the environmental health community will be critical to ensure the safety and sustainability of new technologies.
Phthalate plasticizers: Occurrence and toxicityPhthalates are diesters of 1,2-benzenedicarboxylic acids (phthalic acids) with chemical characteristics that depend on the nature of the side-chains [5]. Since phthalate additives in plastic are not covalently linked to the host polymer, they can leach into the environment [6]. Although they are generally nonpersistent, contamination in the environment is still significant due to widespread use; low-and highmolecular-weight phthalates are commonly found in household dust, soil, and indoor and outdoor air, and as detectable residues in foods [5]. Phthalate exposures may occur through ingestion, inhalation, dermal absorption, and parenteral administration [7]. Several studies have shown that some phthalates possess endocrine-disrupting effects in male rat offspring, following in utero or lactational exposure, which manifest as hypospadias, cryptorchidism, testicular cancer, decreased testosterone levels, and reduced semen quality [5]. Phthalate activation of peroxisome proliferator-activated receptors alpha and gamma (PPARα and PPARγ), adjuvant activity, induction of cell proliferation, suppression of apoptosis, oxidative DNA damage, and production of reactive oxygen species (ROS) have been implicated as well [8][9][10][11]. It has been proposed that oral exposure in rats and humans allows diethylhexyl phthalate (DEHP) to enter the gastrointestinal tract, where it is rapidly metabolized to mono-(2-methylhex...