User:CiKay/sandbox

Group Members: CiKay, Mbeez, Bellre

We are part of an Environmental Disruptors of Development course, in which we are working to help expand the plastic pollution article. This sandbox will host the draft article throughout this process.

Introduction

Plastic pollution involves the accumulation of plastic products in the environment that adversely affects wildlife, wildlife habitat, and or humans. Exposure to many of the chemicals that these plastics are composed of can also cause adverse effects. Plastic pollutants are categorized into micro-, meso-, or macro debris, based on size. Plastic pollution can adversely affect lands, waterways and oceans. Living organisms can also be affected through entanglement, direct ingestion of plastic waste, or through exposure to chemicals within plastics that cause interruptions in biological functions. Plastic reduction efforts have occurred in some areas in attempts to reduce plastic consumption and promote plastic recycling. The prominence of plastic pollution is correlated with plastics being inexpensive and durable, which lends to high levels of plastics used by humans. However it's slow to degrade.

Composition of Plastics

The type of plastic produced is dependent on the components used during production. This, in turn, determines the density of the product. Low-density plastics are less dense than water and are more likely to stay afloat. Examples of low-density plastics are polypropylene and polyethelene. Plastics with a higher density than water include polyethylene terephthalate, polystyrene, and cellulose acetate.

Plastics themselves contribute to approximately 10% of discarded waste. It is estimated that global production of plastics is approximately 225 mt yr^-1. Their abundance has been found to transport persistent organic pollutants, also known as POPs. These pollutants have been linked to an increased distribution to algae associated with red tides.

The following chemicals are commonly found in plastics:

• Bisphenol A: (4,4’-(propane-2,2-diyl)diphenol) is a large component of polycarbonate plastics and of the epoxy resin coating of metal cans.
• Phthalates: (1,2-benzenedicarboxylic acid) are found in many plastics and plasticizers at a high quantity, in order to make them more malleable.
  • Diisononyl phthalate: is used as a plasticizer to give polycinyl chloride (PVC) products flexibility.

Degradation

Depending on their chemical composition, plastics and resins have varying properties related to contaminant absorption and adsorption. Polymer degradation takes much longer as a result of haline environments and the cooling effect of the sea. These factors are what allow plastic debris to persist in the environment and to be swallowed by wildlife. Recent studies have shown that plastics in the ocean decompose faster than was once thought due to exposure to sun, rain, and other environmental conditions, which results in the release of toxic chemicals such as BPA. However, due to the increase volume of plastics in the ocean, decomposition is slowed down. The Marine Conservancy has predicted the decomposition rates of several plastic products. It is estimated that a foam plastic cup will take 50 years, a plastic beverage holder will take 400 years, disposable diaper will take 450 years, and fishing line will take 600 years to degrade.

Plastic Debris

There are three major forms of plastic that contribute to plastic pollution, of them including microplastics as well as mega- and macro-plastics. Mega- and microplastics have accumulated in highest densities in the Northern Hemisphere, concentrated around urban centers, and water fronts. They are less likely to be found around remote islands and the continental shelf seabed. Both mega- and macro-plastics are found in the form packaging, footwear, and other domestic items that have been washed off ships or discarded in landfills. Fishing-related items are more likely to be found around remote islands. These may also be referred to as micro-, meso-, and macrodebris. Plastic debris is categorized as either primary or secondary. Primary plastics are in their original form when collected. Examples of these would be bottle caps, cigarette butts, and microbeads. Secondary plastics, on the other hand, takes into account smaller plastics that have resulted from degradation of primary plastic debris.

Microdebris

Microdebris are plastic pieces that are as small as 2 µm. Plastic debris that starts off as meso- or macrodebris can become microdebris through collisions and degradation. Microdebris that come from cleaning and cosmetic products are also referred to as scrubbers. Because microdebris and scrubbers are so small in size, filter-feeding organisms often consume them. A 2004 study by Dr. Richard Thompson from the University of Plymouth, UK, found a great amount of microdebris on the beaches and waters in Europe, the Americas, Australia, Africa, and Antarctica.

Mesodebris

Plastic debris that is cylindrical or disk-shaped and 5 mm or less in diameter is labeled as mesodebris, more commonly referred to as nurdles. Nurdles are recycled to make new plastic items, but they easily end up released into the environment during production, because they are very small. They often end up in ocean waters through rivers and streams.

Macrodebris

Plastic debris is categorized as macrodebris when it is larger than 20 mm. Macrodebris are often found in ocean waters, and can have a serious impact on the organisms that live there. Fishing nets have been prime pollutants. Even after they have been abandoned, they continue to trap marine organisms and other plastic debris. Eventually, these ghost nests become too difficult to remove from the water because they become too heavy, having grown up to 6 tons.

Environmental Effects

The distribution of plastic debris is highly variable as a result of certain factors such as wind and ocean currents, coastline geography, urban areas, and trade routes. Human population in certain areas also plays a large role in this. Plastics are more likely to be found in enclosed regions such as the Caribbean. Plastic pollution, more so in the forms of macro- and mega-plastics, potentially serves as a means of distribution of organisms to remote coasts that are not their native environments. This could potentially increase the variability and dispersal of organisms in specific areas that are less biologically diverse. Plastics can also be used as vectors for chemical contaminants such as persistent organic pollutants and heavy metals.

Ocean

Ocean-Based Sources of Ocean Plastic Pollution

Almost 90% of plastic debris that pollutes ocean water, which translates to 5.6 million tons, comes from ocean-based sources. Merchant ships expel cargo, sewage, used medical equipment, and others types of wastes that contain plastic. Naval and research vessels also eject waste and military equipment that are no longer necessary. Pleasure crafts also release fishing gear, and household and other types of waste. These different ships do not have enough storage space to keep these pollutants on the ship, so they are purposely discarded. These plastic items can also accidentally end up in the water through negligent handling. The largest ocean-based source of plastic pollution is discarded fishing gear, responsible for up to 90% in some areas. This equipment includes a variety of traps and nets. (Maybe include Table 1 from Plastics in the Marine Environment). Dumping of waste at sea from ships has been prohibited since 1990 under the international shipping regulation MARPOL Annex V. This regulation is likely to cause a reduction in plastic debris derived from sea transport.

Land-Based Sources of Ocean Plastic Pollution

A little over 10% of plastic debris in ocean water comes from land-based sources, responsible for 0.8 million tons every year. Most waste in the form of plastic in landfills are single-use items such as packaging. Because of plastic’s durability, discarding plastics in this way is merely storing them for some time in the future when accumulation becomes a larger problem. Although disposing of plastic waste in landfills has less of a gas emission risk than disposal through incineration, the former has space limitations. Another concern is that the liners that act as a protective layer between the landfill and environment around it can break, leaking toxins and contaminating the nearby soil and water. Landfills that are located near the ocean results in ocean debris that is carried by wind or through smaller waterways such as rivers and streams. Marine debris can also result from sewage water that has not been efficiently treated, which is eventually transported to the ocean through rivers. Plastic items that have been improperly discarded can also be carried into oceans through storm waters.

Land

• water runoff\contamination

Effects on animals

Entanglement

Entanglement in plastic debris has been responsible for the deaths of many marine organisms, such as fish, seals, turtles, and birds. These animals get caught in the debris and end up suffocating or drowning. Because they are unable to untangle themselves, they also die from starvation or from their inability to escape predators. In a 2006 report known as Plastic Debris in the World’s Oceans, it was estimated that at least 267 different animal species have suffered from entanglement and ingestion of plastic debris. Plastic debris kills an average of 100,000 marine mammals annually, and millions of birds and fishes.

Defects in Animals

The plastic debris problem become more pervasive once it enters the water due to its buoyancy, durability, its ability to be fragmented into microscopic pieces, and its ability to leach toxins during the decomposition process. Bisphenol A and phthalates in plastics negatively affect the development of amphibians and crustaceans at concentrations as low as in the ng-µg range though the biological systems of fish seem most affected at higher concentrations.

• birthrates?

Ingestion of plastics

An estimate of 1.5 million Laysan Albatrosses, which inhabit Midway Atoll, all have plastics in their digestive system. Midway Atoll is halfway between Asia and North America, and north of the Hawaiian archipelago. It’s a remote location, and the plastic blockage has proven deadly to these birds. These seabirds choose red, pink, brown and blue plastic pieces, because of the similarities they share with their natural food source. On the shore thousands of birds corpse can be seen with plastic remaining where the stomach once was. The durability of the plastics is visible amongst these remains. In some instances, the stomach size plastic piles are still present, meanwhile the entire bird skeleton has degraded. As a result of plastic ingestion, the digestive tract can be blocked resulting in starvation. The windpipe can also be blocked, which results suffocation. The debris can also accumulate in the animal’s gut, and give them a false sense of fullness. This causes the animal to stop eating, and results in them starving to death.

Human effects

Through biomonitoring, chemicals in plastics, such as BPA and phthalates, have been identified in the human population. Humans can be exposed to these chemicals through the nose, mouth, or skin. Although the level of exposure varies depending on age and geography, most humans experience simultaneous exposure to many of these chemicals. Average levels of daily exposure are below the levels deemed to be safe, but more research needs to be done on the effects of low dose exposure on humans. Due to the use of chemicals used as additives during plastic production, plastics have a potentially harmful effects that could prove to be carcinogenic or promote endocrine disruption. Some of the additives are used as phthalate plasticizers and brominated flame retardants.

Clinical Significance

Due to the pervasiveness of plastic products, most of the human population is constantly exposed to the chemical components of plastics. 95% of adults in the United States have had detectable levels of BPA in their urine. Exposure to chemicals such as BPA and DEHP, a specific pthalate, have been correlated with disruptions in fertility, reproduction, and sexual maturation.

Bisphenol A affects gene expression related to the thyroid hormone axis, which affects biological functions such as metabolism and development. BPA can decrease thyroid hormone receptor (TR) activity by increasing TR transcriptional corepressor activity. This then decreases the level of thyroid hormone binding proteins that bind to triiodothyronine. By affecting the thyroid hormone axis, BPA expoure can lead to hypothyroidism.

BPA can disrupt normal, physiological levels of sex hormones. It does this by binding to globulins that normally bind to sex hormones such as androgens and estrogens, leading to the disruption of the balance between the two. BPA can also affect the metabolism or the catabolism of sex hormones. It often acts as an antiandrogen or as an estrogen, which can cause disruptions in gonadal development and sperm production.

• Fetal and early childhood exposure
• birthrates
• Cancer rates in adults?
• FDA regulation regarding trace amounts
  • should add a link to plastic degradation; this could be our segue into talking (very briefly) about chemicals in plastics that are known\potentially could lead to endocrine disruption

Reduction efforts

Sources of plastic pollution

According to the United Nations Joint Group of Experts on the Scientific Aspects of Marine Pollution (GESAMP), an estimated 80 percent of the world’s marine pollution comes from land-based sources, and 65 to 95 percent of the waste is plastic debris. This plastic debris waste eventually accumulate overtime to form large masses of floating debris fields in the ocean. The other 20 percent of marine pollution comes from dumping activities on the water.

Recycling

Plastic recycling is a three-part process. The three phases are collection of recyclable materials, reprocessing of recycled materials into new products, and the purchase of recycled products. In 2008 the global consumption of was 260 million tons. A report by Global Industry Analyst estimate the global consumption of plastic to reach 297.5 million tons by 2015.

Biodegradable Plastics

The use of biodegradable plastics has been shown to have many advantages and disadvantages.

Incineration

Up to 60% of used, plastic medical equipment is incinerated rather than deposited in a landfill as a precautionary measure to lessen the transmission of disease. This has allowed for a large decrease in the amount of plastic waste that stems from medical equipment. If plastic waste is not incinerated and disposed of properly, a harmful amount of toxins can be released and dispersed as a gas through air or as ash through air and waterways. Many studies have been done concerning the gaseous emissions that result from the incineration process.

Bans

In Canada, the United States, and the European Union, BPA has been banned from being incorporated in the production of baby bottles and children’s cups, due to health concerns and the higher vulnerability of younger children.

Agencies such as the Environmental Protection Agency and the Food and Drug Administration often do not assess the safety of new chemicals until after a negative side effect is shown. Once they suspect a chemical may be toxic, it is studied to determine the human reference dose, which is determined to be the lowest observable adverse effect level. During these studies, a high dose is tested to see if it causes any adverse health effects, and if it does not, lower doses are considered to be safe as well. This does not take into account the fact that with some chemicals found in plastics, such as BPA, lower doses can have a discernible effect.

• Maybe talk about educational efforts
• EPA plastic pollution policy? -- http://water.epa.gov/type/oceb/marinedebris/prevention_plastics.cfm