What are microplastics, and what are phthalates?
An example of microplastic particles we found while sorting through the stomach contents of a northern fulmar (Fulmarus glacialis) specimen collected from the Western Aleutian Islands.
Plastic debris can cause physical harm to wildlife, however, plastic ingestion does not always result in ulcerations, starvation or death for seabirds. In the marine environment, plastic debris continuously degrades into much smaller “microplastics,” which are more easily carried by ocean currents and more easily mistaken for small prey items such as plankton (Moore 2008). For example, microparticles and nanoparticles fall within the size range of the staple phytoplankton diet of zooplanktons such as the Pacific Krill (Andrady 2011). Some species of seabirds are ingesting microplastics and are likely not starving to death as a consequence. These microplastics can pass through an animal’s stomach and intestine, where chemicals leach off these particles and may get incorporated into the animal’s tissue, as plastics are coated in toxic chemicals, such as phthalates, that can be metabolized upon exposure. Even more troubling is that plastics absorb other toxic chemicals in the marine environment. High concentrations of hydrophobic organic contaminants, or persistent organic pollutants (POPs), such as polyaromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) have been measured on plastic debris collected from the environment (Endo et al. 2005, Rios et al. 2007). Toxin exposure can negatively alter normal neurodevelopment, and consequently the development of complex brain functions and behaviors (Holahan and Smith 2015). Research suggests that developing organisms such as embryos and neonates are more negatively impacted by exposure to low levels of toxic chemicals than adult organisms (Carruthers and Foster 2005).
General chemical structure of a phthalate, the R and R' are placeholders for the various chemical chains since there are 25 types of phthalates in existence.
Phthalates are chemicals of particular concern for organisms in the marine environment. Phthalates are known as plasticizing chemicals, a group of chemicals added to basic plastic material to impart specific qualities. They are colorless, odorless, oily liquids that are diesters of phthalic acid with low volatility and low water solubility (Lyche et al. 2009), with 25 known types manufactured. Phthalates are classified into three categories based on the length of the ester side chains: low molecular weight, high molecular weight and transitional or mid-molecular weight, and health impacts are related to the length of the ester side chain (Holahan and Smith 2015). These chemicals impart flexibility, pliability, and elasticity to plastic polymers (Halden 2010). Because phthalates are not bound to a polymer matrix, they are highly susceptible to leaching, which is cause for concern as they make up about 70% of the US plasticizer market (Halden 2010). Annually, over three million metric tons of phthalates are consumed worldwide (Lyche et al. 2009). Ecological factors such as oceanic and air currents and migratory species have aided the spread of phthalates (Heudorf et al. 2007). They are ubiquitous in the environment, and have been detected in soils (Bauer and Herrmann 1997, Cartwright et al. 2000), surface water (Taylor et al. 1981, Staples et al. 1997, Horn et al. 2004), as pollutants in indoor air (Becker et al. 2004) and in the atmosphere (Thuren and Larsson 1990), the tissue of mammals (Staples et al. 1997), as well as in several aquatic species (Wofford et al. 1981).
Phthalates are endocrine disrupting compounds (Latini 2005, Kamrin 2009, Meeker et al. 2009), which are natural or synthetic compounds that mimic or interfere with the biosynthesis, metabolism or action of endogenous hormones and thus, interfere with homeostatic maintenance (Crisp et al. 1998). Numerous endocrine disrupting chemicals have been released into the environment since World War II (Colborn et al. 1994). They are considered an emerging environmental contaminant due to the endocrine disruption and carcinogenic effects detected in laboratory animal experiments and in humans. These chemicals pose a health risk as estrogen receptor expression is associated with many components of the human body, including the brain, immune system, cardiovascular system, lungs, mammary glands, liver, kidneys, reproductive system, adipose tissue, and bone (Mueller 2004).
Please find a few more links to more details about environmental contaminants and news articles related to them:
EPA, Persistent Organic Pollutants: A Global Issue, a Global Response
ToxTown: Environmental health concerns and toxic chemicals where you live, work and play
NRDC: 9 Ways to avoid hormone-disrupting chemicals
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