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Human health and plastics

Plastic is one of the most widely used and recognized materials today. Since its mass production in the 1950’s, plastics have been produced in abundance around the world. Plastics are preferred for their physical properties of being flexible and durable, while also being cost efficient. Despite the many positive benefits that plastics offers, the negative impact of plastics has become a global problem that is effecting many scopes of human life and our environment.

Plastic is not sustainable at its current usage. Plastic as packaging and as single-use products are often thrown away in less than a year after being manufactured. (Hopewell, et al. 2009) This waste has been rapidly accumulating worldwide, consistently being dumped, without thought, on land and in waterways.

Humans are inevitably exposed to plastic pollution in a variety of ways because of the careless continual methods in which plastics are disposed of at the end of their life cycle. The various chemical additives in plastics have a strong tendency to leach in whatever environment that they are discarded in. These chemicals expose humans to harmful toxins which have been linked to adverse health issues. Chemical exposure from plastics can be ingested by food and water, inhaled through air contamination, and even by transdermal contact. Plastics do not naturally degrade to a great extent. So, chemicals leaching from the plastics can easily contaminate soil and enter waterways via landfills.

Two particular chemicals have become infamous as harmful plastic toxins are Phthalates and Bisphenol-A.

It is estimated that 11 billion pounds of phthalates are produced worldwide every year. (Mankidy, Wiseman et al. 2013) Several million tons of phthalates are used annually in the world as plasticizers for the manufacture of plastics and other products. (Christova-Bagdassarian, 2014) Phthalates are not chemically bonded to plastics derived of them and can therefore easily leach into the environment around them. The most important plasticizers are DEHP, DINP and DIDP, which according to data from 2003 accounted over 75% of total European phthalates consumption and exceed the amount of 1 million tonnes. Other common phthalates are DMP, DEP, DiBP, DnBP and BBP. (Christova-Bagdassarian, 2014)

Phthalates have many applications. “Phthalates, which are esters of phthalic acid are primarily used to enhance plasticity of industrial polymers. They are used in a number of consumer end products such as toys, paints, adhesives, lubricants, packaging and building materials, personal care items, electronics, medical devices, and are an unavoidable part of modern life. (Mankidy, Wiseman et al. 2013) The most commonly used phthalate is DEHP, mainly for softening and increasing the flexibility of PVC for medical devices (tubing and packages for intravenous transfusions), food packaging items for bath, some floor and wall coverings. (Christova-Bagdassarian, 2014)

Bisphenol-A, or BPA has an estimated production of 5.5 million metric tons yearly. (Rochester 2013) “Thus, over 100 t of BPA are released into the atmosphere every year of production (Rezg, El-Fazaa et al. 2014) “BPA has been used in many consumer products, including plastics (as a polymer, i.e. polycarbonate[#7] plastic), PVC, food packaging, dental sealants, and thermal receipts. Humans are exposed to BPA through their diet, inhalation of household dust, and dermal exposure.” (Rochester 2013)

Even purchasing food items packaged in plastic can contribute to human exposure through the leaching of the chemicals from the plastic into the food. When heated or exposed to radiation, the chemicals in the plastic can start to leach. “When food packaging is sanitized, for example, using gamma radiation or ethylene oxide, chemicals can leach into foods. Gamma radiation is known to break down the carbon-chlorine bonds of polyvinyl chloride plastics and some plastic additives. These by-products of the breakdown process then might migrate into food.” (Chemical Migration & Package Leaching. May 2010;:1-11. Available from: Food Science Source, Ipswich, MA.)

Even daily interactions such as touching receipt paper can allow transdermal absorption of BPA through human skin. “In most cases, the total amount of BPA on the receipt was at least one thousand times the amount found in the epoxy lining of a food can, another controversial use of the chemical.”(Lu, Chang et al. 2013) “BPA exists in thermal papers as a monomer without chemical bonds, which enhances its absorptivity into the human skin when people come in contact with thermal papers. Nowadays, people contact cash register receipts frequently in their daily life, so it is important to estimate the exposure risk to BPA, especially for certain categories of people (e.g. cashier) who handle receipts frequently.”  (Lu, Chang et al.)

Human vulnerability to plastic exposure

Humans are found to be susceptible to BPA by a battery of tests. The constant exposure to leaching chemicals is confirmed by the frequency in detection in humans of all age ranges. “BPA is detectable in the urine of almost all adults and children tested, as well as in the serum of pregnant women, breastmilk, follicular and amniotic fluid, cord blood and placental tissue, and human fetal livers, which indicates BPA exposure is prevalent in utero in developing fetuses.” (Rochester 2013)

Likewise, the exposure to phthalates is also widely detected. “In humans, phthalates have been detected in matrices such as blood, urine, saliva, amniotic fluid, breast milk and cord blood. The major pathway of exposure to phthalates is the oral route, though inhalation and dermal absorption may play a significant role in exposure. Infants and toddlers are the most vulnerable receptors because: (1) they exhibit more hand-to-mouth activity, and (2) consume the most food as a percent of their body weight. (Mankidy, Wiseman et al. 2013)

BPA and phthalates not only affect humans, but also wildlife. “Phthalates have been reported to affect multiple biochemical processes in humans and wildlife. These include effects on reproduction, damage to sperm, early onset of puberty in females, anomalies of reproductive tract, infertility and adverse outcomes of pregnancy, to neurodevelopment and allergies. Because humans and wildlife can be exposed simultaneously to several phthalates any assessment of the risks posed by phthalates needs to consider combined effects of all of the phthalates in mixtures.”  (Mankidy, Wiseman et al. 2013)

Plastic pollution in habitats around the world

A large body of evidence (over 300 published studies) links BPA to adverse health effects in mammalian and non-mammalian laboratory, wildlife, and in vitro models.” (Rochester 2013) Marine environments are a growing source of plastic pollution. Debris from human trash and shipping wastes continue to add to the source of plastic found around the oceans all over the world. “Large amounts of plastic bags, styrofoams, rubbers, fishing lines and other hard-to-degrade plastic materials collect in the marine environment and may float for decades. Derraik (2002) estimated that between 60 and 80% of all marine debris is plastic polymer-based. The source of this plastic debris is both land and sea-based. It has been estimated that ocean going vessels dispose of between 4 and 6.5 million metric tons of plastic each year. More recent UNEP (2005) figures estimate a total of around 20 million metric tons of plastic from both land and sea sources, with land-based sources making up 80% of that total figure.”(Muller, Townsend et al. 2012)

Plastics interaction with the ocean environment

Plastics can degrade to a certain extent in nature by photodegradation. Over time photodegradation from the sun contributes to breaking down of the plastic to smaller sizes. However, when plastics are exposed to a marine environment, the photodegradation process is greatly decreased since the seawater is lower in temperature and oxygen availability. (Webb,Crawford, et al. 2013)

Even degradable plastics are harmful to marine life and are not a clear solution. “Although biodegradable polymers may be an important improvement, their degradation in salt water is much slower than that claimed by the manufacturer (approx 3 years vs 49 days). This rate still represents a major improvement in the long-term (compared to thousands of years needed for standard plastics to degrade), yet these bags still pose a short-term threat to marine animals. (Muller, Townsend et al. 2012)

Danger for sea life

A substantial amount of the plastic waste in the ocean is neustonic while other plastics sink in the ocean depths. The danger to marine creatures is inevitable by the plastic contamination which effects all levels of the ocean life. Plastic segments can entangle around the marine animals preventing movement, breathing, or digestion.  “To date, over 177 marine species have been recorded to ingest man-made polymers that cause life-threatening complications such as gut impaction and perforation.”(Muller, Townsend et al. 2012)

The smaller plastic fragments or microplastic, which is defined as smaller than 1mm, presents another problem for sea life. The colorful microplastics are mistaken for food and ingested. “These small marine plastics are a toxic hazard to food webs since they can contain harmful compounds from the manufacturing process (e.g. Bisphenol A), as well as contaminants adsorbed from the surrounding water (e.g. polychlorinated biphenyls). These substances can be carried across marine regions and transferred from plastics to a wide range of organisms, from zooplankton and small fish to whales. Furthermore, they can physically damage suspension- and deposit-feeding fauna (e.g. internal abrasions and blockages after ingestion), and alter pelagic and sediment-dwelling biota by modifying physical properties of their habitats. Finally, these small marine plastics can transport rafting species, potentially changing their natural ranges to become non-native species and even invasive pests.” (Reisser, Shaw et al. 2014) Various sizes of marine creatures have ingested plastics from loggerhead turtles, myrid shrimp, whales, many species of fish, and birds living near the ocean shore. Ingestion of microplastic can block digestion organs can and result in starvation leading to death. Plastic has been found through dissection in intestinal organs in birds, turtles, and fish.

Also, discarded microbeads from personal care products contributes to the pollution. “Once released to the environment, microbeads form nuclei of collected contaminants and may enter the food chain. It is not possible to collect microplastics in any meaningful amount once dispersed in water without damaging the aquatic ecosystem. Microbeads make up only a small percentage of plastic pollution. However, they are unique in that their release as water pollutants is an inevitable part of their lifecycle and is anticipated by their manufacturers.”  (Doughty, Eriksen 2014)

Aquaculture – another source of plastic

Aquaculture operations along the seashores are also a source of plastic waste in the oceans. Polystyrene is heavily used and has been found in high quantity in the surrounding waters of Chile’s salmon and mussel aquaculture and also in Japan’s oyster culturing shores. “The mixture of the [polystyrene] monomer itself, chemicals from the manufacturing process, and those sorbed from the environment may act as a multiple Stressor to several species that ingest [polystyrene] debris. The enormous amount of uncovered expanded polystyrene docks and floats used in aquaculture and its tendency to readily fragment means that untold trillions of particles the size of plankton and fish eggs are becoming a part of the marine food web.” (Moore, 2014)

Outside of polystyrene, olefins are another group of plastic contaminants. Polypropylene, polyethylene and PVC are frequently used as components in aquaculture operations. Polypropylene and polyethylene have been studied to release high level of pollutants on beaches from discarded plastics. The older plastic released a greater amount of toxins. Another study, showed pathological changes to liver in fish exposed to these types of plastic. (Moore, 2014) Polyvinylchlorine, or PVC, is a devastating plastic to the ocean environment. “PVC contains a small percentage of nonpolymerized vinyl chloride capable of leaching into liquids with which it comes in contact. The EPA’s “maximum contaminant level goal” for vinyl chloride is zero.” Such persistent, bioaccumulative toxic substances are linked with endocrine hormone disruption, “decreased fish populations and reduced species evenness and richness.” (Moore, 2014)

Toxins in sealife

In 2013, one study demonstrated that in sealife, 19% of the species evaluated “contained some form of marine debris, the majority of which was some form of plastic or fishing-related line. Surprisingly, species with the highest incidences of debris ingestion are thought to be primarily mesopelagic and unlikely to come into contact with surface waters containing known debris fields.” (Choy, 2013)

From the continual exposure and ingestion of plastic chemicals, our sea life is also experiencing health concerns. Plastic chemicals disrupt endocrine function in animals. “Styrene, a monomer of several plastic types including polystyrene, rubber and acrylonitrile– butadiene–styrene, and bisphenol-A, a monomer of polycarbonate, can disrupt endocrine system function. Furthermore, there is evidence that UV-stabilizers, phthalates and nonylphenol, additives to plastic, are estrogenic and/or antiandrogenic.” (Rochman, Kurobe et al. 2014) The impact of these chemical pollutions from plastic is yet to fully be determined in marine life. Endocrine and reproductive disruptions may cause interfere with sea life population.

Ocean Gyres

The production rate of plastic has grown substantially since its conception in the 1950’s. However, plastic has also grown to become a major source of pollution in the marine environment. Marine plastic pollution has significant environmental, economic, cultural, and aesthetic costs. (Avery-Gomm, 2013) Plastic is now found in every ocean of the world, including those formerly thought of as pristine, such as the Arctic Ocean and Southern Ocean. (Avery-Gomm, 2013) “Ocean currents could carry debris and pollutants around the world over a long range. Plastic pollution was discovered in sun Antarctica and Antarctic coasts. It has been demonstrated that organic pollution could be carried by sea debris and transported globally. (Cheng, 2013)

Ocean debris has been assessed to be 60 – 80% petroleum-based plastic. Plastic pollution enters the marine environment via rivers, beaches, maritime activities, and illegal dumping at sea. By methods of photodegradation and hydrolysis, plastic loses its elasticity, and powered by wind and waves, gradually breaks into smaller particles. (Eriksen, 2013)

Plastic debris migrates into subtropical gyres where it forms accumulation zones of microplastic particles distinct from surrounding waters relatively free of plastic pollution. These gyres are formed by surface currents that are primarily a combination of Ekman currents driven by local wind and geostrophic currents maintained by the balance between sea level gradients and the Coriolis force. (Eriksen, 2013)

North Pacific Gyre

North pacific is the largest ocean gyre. In the north Pacific central gyre, researchers found over 5 tons of plastic debris per square kilometer. In the north Atlantic subtropical gyre, a distinct debris gradient was found. The center of the gyre contained more than 15000 pieces of plastic debris per square kilometer, whereas the density was only about 5000 pieces per square kilometer along the edges of the gyre. In the areas closest to land, the lowest densities of plastic debris were found at less than 2500 pieces per square kilometer. (Cheng, 2013)

South Pacific

An abundance of plastic pollution has been surveyed in the South Pacific gyre. The average abundance and mass was 26,898 particles km_2 and 70.96 g km_2, respectively. 88.8% of the plastic pollution was found in the middle third of the samples with the highest value of 396,342 particles km_2 occurring near the center of the predicted accumulation zone.(Eriksen, 2013) The density is predicted to be as high as much as ten times higher than the maximum density in the North Atlantic. (Eriksen, 2013)

North Atlantic

The data from the plastic content has been surveyed at the surface of the western North Atlantic Ocean and Caribbean Sea from 1986 to 2008. More than 60% of 6136 surface plankton net tows collected buoyant plastic pieces, typically millimeters in size. The highest concentration of plastic debris was observed in subtropical latitudes and associated with the observed large-scale convergence in surface currents predicted by Ekman dynamics.” (Law, 2010)

South Atlantic Gyre

In one study, the surveyed amount of litter counts in the South Atlantic gyre was 79 h, which covered 1963 km. (Ryan, 2014) The debris included a plethora of plastic related articles. “Plastic items were divided into packaging (bottles, tubs/cups, lids and lid-rings, bags, food wrapping, polystyrene, and other packaging such as packing strips, etc.), fishery-related plastic articles (ropes and nets, floats, and other fishing gear such as fish trays), other plastic user items (designed for repeated use, unlike packaging, divided into three categories: buckets, shoes/gloves/hats, and other user items…(Ryan, 2014)

Indian Gyre

“The California-based 5 Gyres research group recently completed the first global estimate of rubbish volumes in the world’s oceans, ranking the Indian Ocean the third worst behind the North Pacific and Atlantic.” (Le May, 2014) The majority of the plastic pollution “came from commercial ships losing and dumping gear overboard, dense coastal populations and catastrophic events such as tsunamis and hurricanes.”(Le May, 2014)

Our oceans are suffering because of plastic pollution. Petroleum in any form entering the marine environment by anthropogenic means is a pollutant. A wide range of marine life, including marine mammals, reptiles and birds, is impacted by plastic pollution through entanglement or ingestion and the persistent organic pollutants that sorb onto plastic. (Eriksen, 2013)

Environment and Plastic pollution

The plastic industry is estimated to grow by 15% per year. Sadly, “By 2009, fully 40% of all plastic produced was for single-use (throw-away) items — a terrible waste of a finite resource.” (Nelson, 2014)

The production process consumes about 10% of oil and gas both produced and imported by the U.S.  Globally, the production of plastic accounts for 270 million tons of oil and gas in order to meet the supply for energy and materials. As expected, the greenhouse emissions for the annual plastic production rate is considerably high. “Associates quantified the global warming potential for several plastic resins, with values ranging from 1.477 kg CO2 equiv/kg resin for the production of low-density polyethylene (LDPE) to 3.149 kg CO2 eq/kg resin for the production of acrylonitrile butadiene styrene (ABS).” (Rostkowski, 2012)

When a plastic’s usefulness is over, it is readily dumped in landfills and in the ocean environment. “Plastics occupy about 20% of landfill volume and can persist for over 2,000 years.” (Rostkowski, 2012) The resistance in the breakdown of plastic is not surprising. Plastic has become a popular choice because of its “exceptionally high stability and durability.

There are four mechanisms by which plastics degrade in the environment: photodegradation, thermooxidative degradation, hydrolytic degradation and biodegradation by microorganisms. Generally speaking, natural degradation of plastic begins with photodegradation, which leads to thermooxidative degradation. Ultraviolet light from the sun provides the activation energy required to initiate the incorporation of oxygen atoms into the polymer. This causes the plastic to become brittle and to break into smaller and smaller pieces, until the polymer chains reach sufficiently low molecular weight to be metabolised by microorganisms. These microbes either convert the carbon in the polymer chains to carbon dioxide or incorporate it into biomolecules. However, this entire process is very slow, and it can take 50 or more years for plastic to fully degrade. This is not aided by the fact that the photodegradative effect is significantly decreased in seawater due to the lower temperature and oxygen availability and that the rate of hydrolysis of most polymers is insignificant in the ocean.” (Webb, 2013.)

Through photodegradation and other environmental factors, the plastics can be broken down into smaller sizes and start to leach chemicals into nature. Other concerns include in-use leaching of potentially harmful additives, such as bisphenol A (BPA) and phthalates, and release of unwanted residues during incineration (e.g., dioxins, sulfur oxides, hydrogen chloride, cadmium, lead, zinc, and arsenic).” (Rostkowski, 2012)

Chemical lechates from plastics

Bisphenol A

“BPA can be released into the atmosphere via industrial production with a rate of some 100 t year_1 (Staples et al., 1998). Sidhu et al. (2005) estimated the emission of BPA to be over w75,000 kg year_1 in the United States based on an uncontrolled domestic waste burning experiment.” (Fu and Kawamura 2010)

BPA has been confirmed as an atmospheric pollutant, “more than 260 atmospheric aerosol samples were collected from various cities in Japan, China, India and New Zealand, as well as remote sites including the Pacific, Indian and Atlantic Oceans and the Polar Regions.” “The detection of BPA in ambient aerosol samples from urban, rural, marine and the polar regions indicates that it is a ubiquitous component in the atmosphere. The open burning of plastics in domestic wastes was found to be a significant emission source of atmospheric BPA in urban regions.”(Fu and Kawamura 2010)

Phthalates

Phthalates are not chemically bonded to the plastics and are released continuously into the air. They can penetrate everywhere in the environment, but they are not in high concentrations due to biodegradation processes, photodegradation, and anaerobic degradation.  Higher levels are found in more urban areas and more in the indoor than in outdoor air.” (Christova-Bagdassarian, 2014)

Organophosphorus Esters

Another group of atmospheric pollutants are organophosphorus esters. “Unlike other additives, OPEs are only physically mixed with plastics, thus they are not covalently bonded to the plastic polymers, facilitating their desorption and release into the environment. Hence, they have been found almost everywhere in the world, including indoor environments, precipitation, rivers waters, ocean waters and aerosols, montane lakes, and even in humans. (Cheng, 2013)

Elevated exposure to OPEs have been shown to cause cancer, disturb nerve conduction, cause skin allergy, affect reproduction, and their toxicity has also been shown at environmentally relevant concentrations. Furthermore, degradation experiments reveal that some of the OPEs may be persistent in the environment, especially chlorinated alkyl OPEs in ocean water. (Cheng, 2013)

Oceans pollution from plastics

“Over 250 marine species are believed to be impacted by plastic ingestion.”(Wright, 2013)

“A technical report considering the impacts of marine debris on biodiversity revealed that over 80% of reported incidents between organisms and marine debris was associated with plastic whilst 11% of all reported encounters are with microplastics.” (Wright,2013)

Microplastics “…increase the total surface area available for absorption of toxins and pseudoestrogens. The microplastics are like sponges soaking up agricultural fertilizers and other toxins in the water. Then those microplastics are eaten by marine life and their toxins apparently magnified and passed up the food chain.”(Nelson, 2014) “The 300 mm mesh size is most commonly used to sample microplastics at sea.” (Ivar do Sul and Costa 2014)

“Several persistent organic pollutants (POPs) bind to plastic as it is transported throughout a watershed, buried in sediment, or floating in the ocean.” A single pellet may attract up to one million times the concentration of some pollutants as the ambient seawater,” making those chemicals readily available to marine life. Food mimicry, based on color, shape, or presence of biofilms, is one mechanism driving wildlife to ingest plastics, in addition to filter feeding and respiration. Once in the stomach POPs may desorb due to changes in pH, temperature, or the presence of surfactants.” (Eriksen, 2014)

From this environmentally unfriendly cycle, plastic has caused pollution on a global scale in land, sea, and air. “Environmental microplastics are available to every level of the food web, from primary producers to higher trophic-level organisms.”(Ivar do Sul and Costa 2014)

Landfills and Plastic pollution

Plastics in the waste stream are dealt with in one of three ways: incineration, burial, or recycling. Incineration, used to dispose about 16% of all municipal wastes in developed countries burn garbage in waste-to-energy facilities that use heat energy to generate steam or electricity. Because plastics are typically derived from petroleum or natural gas, they can generate almost as much energy as fuel oil, although the much higher amount of energy initially required to produce the plastic is lost. Potential hazardous emissions from incinerating plastics include hydrogen chloride, dioxin, cadmium, and fine particulate matter. Even with stricter air pollution standards in place, there is considerable public opposition to incineration. (Rustagi, 2011)

Land filling plastics is generally a benign practice because plastics are chemically inert. Some additives to plastics do provoke concern as they may migrate from the plastics into the leachate. Plasticizers known as phthalates are hazardous substances and have been found in a number of leachate analyses at various concentrations. A more significant problem for land filling is that plastic wastes now constitute about 10% by weight and about 20% by volume of the municipal waste stream. Since plastics are essentially nondegradable, their volume will not shrink and plastics may eventually consume a disproportionate amount of landfill space. (Rustagi, 2011)

Recycling is a four-part exercise of collecting a mix of plastics at curbside or drop-off centers, sorting the plastics into the six types, reclaiming the plastic by physically or chemically converting them to flakes or pellets, and then processing the flakes or pellets into a final product. One reason plastics are recycled less often than glass or metal is because the sorting step is very labor-intensive and, hence, expensive. However, the cost and accuracy of sorting are crucial elements in making plastics recycling economically viable because each type of plastic has different performance characteristics that make it best suited for specific applications. (Rustagi, 2011)