FACTS ABOUT PLASTIC
What Is Plastic?
A simple definition could be: any of a group of synthetic or natural organic materials that may be shaped when soft and then hardened, including many types of resins, resinoids, polymers, cellulose derivatives, casein materials, and proteins: used in place of other materials, as glass, wood, and metals, in construction and decoration, for making many articles, as coatings, and, drawn into filaments, for weaving. They are often known by trademark names, as Bakelite, Vinylite, or Lucite.
In chemistry, plastics are large molecules, called polymers, composed of repeated segments, called monomers, with carbon backbones. A polymer is simply a very large molecule made up of many smaller units joined together, generally end to end, to create a long chain. The smallest building block of a polymer is called a monomer. Polymers are divided into two distinct groups: thermoplastics (moldable) and thermosets (not). The word “plastics” generally applies to the synthetic products of chemistry.
Alexander Parkes created the first man-made plastic and publicly demonstrated it at the 1862 Great International Exhibition in London. The material, called parkesine, was an organic material derived from cellulose that, once heated, could be molded and retained its shape when cooled.
Many, but not all, plastic products have a number – the resin identification code – molded, formed or imprinted in or on the container, often on the bottom. This system of coding was developed in 1988 by the U.S.-based Society of the Plastics Industry to facilitate the recycling of post-consumer plastics. It is indeed, quite interesting to go through the fine lines.
- Polyethylene terephthalate (PET or PETE) – Used in soft drink, juice, water, beer, mouthwash, peanut butter, salad dressing, detergent, and cleaner containers. Leaches antimony trioxide and (2ethylhexyl) phthalate (DEHP).
- DEHP is an endocrine disruptor that mimics the female hormone estrogen. It has been strongly linked to asthma and allergies in children. It may cause certain types of cancer and it has been linked to negative effects on the liver, kidney, spleen, bone formation, and body weight. In Europe, DEHP has been banned since 1999 from use in plastic toys for children under the age of three.
- High-density polyethylene (HDPE) – Used in opaque milk, water, and juice containers, bleach, detergent and shampoo bottles, garbage bags, yogurt and margarine tubs, and cereal box liners. Considered a safer plastic. Research on risks associated with this type of plastic is ongoing.
- Polyvinyl chloride (V or Vinyl or PVC) – Used in toys, clear food and non-food packaging (e.g., cling wrap), some squeeze bottles, shampoo bottles, cooking oil and peanut butter jars, detergent and window cleaner bottles, shower curtains, medical tubing, and numerous construction products (e.g., pipes, siding). PVC has been described as one of the most hazardous consumer products ever created. Leaches di (2-ethylhexyl) phthalate (DEHP) or butyl benzyl phthalate (BBzP), depending on which is used as the plasticizer or softener (usually DEHP). DEHP and BBzP are endocrine disruptors mimicking the female hormone estrogen; have been strongly linked to asthma and allergic symptoms in children; may cause certain types of cancer; and linked to negative effects on the liver, kidney, spleen, bone formation, and body weight. In Europe, DEHP, BBzP, and other dangerous phthalates have been banned from use in plastic toys for children under three since 1999. Not so elsewhere, including Canada and the United States.
Dioxins are unintentionally, but unavoidably, produced during the manufacture of materials containing chlorine, including PVC and other chlorinated plastic feedstocks. Dioxin is a known human carcinogen and the most potent synthetic carcinogen ever tested in laboratory animals. A characterization by the National Institute of Standards and Technology of cancer causing potential evaluated dioxin as over 10,000 times more potent than the next highest chemical (diethanol amine), half a million times more than arsenic, and a million or more times greater than all others. - Low-density polyethylene (LDPE) – Used in grocery store, dry cleaning, bread and frozen food bags, most plastic wraps, and squeezable bottles (honey, mustard). Considered a safer plastic. Research on risks associated with this type of plastic is ongoing.
- Polypropylene (PP) – Used in ketchup bottles, yogurt and margarine tubs, medicine and syrup bottles, straws, and Rubbermaid and other opaque plastic containers, including baby bottles. Considered a safer plastic. Research on risks associated with this type of plastic is ongoing.
- Polystyrene (PS) – Used in Styrofoam containers, egg cartons, disposable cups and bowls, take-out food containers, plastic cutlery, and compact disc cases. Leaches styrene, an endocrine disruptor mimicking the female hormone estrogen, and thus has the potential to cause reproductive and developmental problems. Long-term exposure by workers has shown brain and nervous system effects and adverse effects on red blood cells, liver, kidneys, and stomach in animal studies. Also present in secondhand cigarette smoke, off gassing of building materials, car exhaust, and possibly drinking water. Styrene migrates significantly from polystyrene containers into the container’s contents when oily foods are heated in such containers.
- Other – This is a catchall category that includes anything that does not come within the other six categories. As such, one must be careful in interpreting this category because it includes polycarbonate – a dangerous plastic – but it also includes the new, safer, biodegradable bio-based plastics made from renewable resources such as corn and potato starch and sugar cane. Polycarbonate is used in many plastic baby bottles, clear plastic sippy cups, sports water bottles, three and five gallon large water storage containers, metal food can liners, some juice and ketchup containers, compact discs, cell phones, computers. Polycarbonate leaches Bisphenol A (some effects described above) and numerous studies have indicated a wide array of possible adverse effects from low-level exposure to Bisphenol A: chromosome damage in female ovaries, decreased sperm production in males, early onset of puberty, various behavioral changes, altered immune function, and sex reversal in frogs.
Rob Krebs of the American Plastics Council notes that people value plastics for exactly what creates the most problems at sea and on lands: their durability.
Plastic debris, of all sizes and shapes, is a transboundary pollution problem with a powerful vehicle, the ocean.
Vacha Dam near town of Krichim, April 25, 2009. Photo: Dimitar Dilkoff
BUOYANCY
Plastics travel long distances. Their distribution in the oceans isn’t uniform, yet they are omnipresent from the Polar Regions to the Equator. Scientists are still refining methods to detect and analyze the materials. A good example of plastic debris’ buoyancy is as follows. In 1992, twenty containers full of rubber ducks were lost overboard from a ship traveling from China to Seattle. By 1994, some had been tracked to Alaska, while others reached Iceland in 2000. The ducks (with a distinctive logo on their base) have been sighted in the Arctic, Pacific and Atlantic Oceans (Ebbesmeyer, 2003).
PHOTODEGRADATION VS. BIODEGRADATION
Plastic is generally a durable material. Its durability has made the culprit of the problem since it is considered resistant to natural biodegradation processes, i.e. the microbes that break down other substances do not recognize plastic as food. Yet plastic can be fragmented with the effects of UV, being broken down by light in smaller and smaller debris over time.
Biodegradation, the breaking down of organic substances by natural means, happens all the time in nature. All plant-based, animal-based, or natural mineral-based substances will over time biodegrade. In its natural state raw crude oil will biodegrade, but man-made petrochemical compounds made from oil, such as plastic, will not. Why not? Because plastic is a combination of elements extracted from crude oil then re-mixed up by men in white coats. Because these combinations are man made they are unknown to nature. Consequently, it has been thought that there is no natural system to break them down. The enzymes and the micro organisms responsible for breaking down organic materials that occur naturally such as plants, dead animals, rocks and minerals, don’t recognize them. This means that plastic products are said indestructible, in a biodegradable sense at least.
In sum, as time passes, we know that plastic will eventually photo-degrade, i.e. break down into smaller and smaller fragments by exposure to the sun. The photo-degradation process continues down to the molecular level, yet photo-degraded plastic remains a polymer. No matter how small the pieces, they are still and always will be plastic, i.e. they are not absorbed into or changed by natural processes. At sea, the plastic fragmentation process occurs as well, due to wave, sand action, and oxidation. Estimates for plastic degradation at sea has been ranged from 450 to 1,000 years.
Of particular concern are the floating small plastic fragments often referred in the media to as mermaids’ tears, which are tiny nurdles of raw plastic resin that form the building material of every manufactured plastic product, or are granules of domestic waste that have fragmented over the years. Dr Richard Thompson of the University of Plymouth, UK has identified plastic particles thinner than the diameter of a human hair. But while they cannot be seen, those pieces are still there and are still plastic. Not absorbed into the natural system, they just float around within it. He estimates that there are 100,000 particles of plastic per sq km of seabed and 300,000 items of plastic per sq km of sea surface.
Either way, mermaid tears, or fragmented plastic debris, reaching microscopic size over time, remain everywhere and are almost impossible to clean up. They are light enough to float in the wind, landing in the earth’s oceans. Mermaid’s tears are often found in filter feeders like mussels, barnacle, lugworm and amphipods.
Thus, the photo degradation of plastic debris makes the matter worse. Plastic becomes microscopic, invisible, yet ever polluting waters, beaches, coasts, seafloor, being eaten by even tinier marine organisms, therefore entering the food chain insidiously and ineluctably.
TOXIC SPONGE
Corroborating reports and findings worldwide demonstrated that fragmented plastics debris’ increase and massive presence on and off shores does constitute reason for raised worries and awareness.
Studies on small plastic pellet by Dr Richard Thompson and by Hideshige Takada, Yukie Mato professor of organic geochemistry at Tokyo University, have shown that plastic debris meeting other pollutants in the oceans absorbs harmful chemicals from the sea water they float in, acting like a pollution sponges.
These studies have been conducted on plastic nurdles not just because of their uniform size and shape, thus easier to study and compare by scientifics, but also because of their wide spread presence on the world’s beaches.
In UK, mermaid tears are the second common plastic litter found on the beaches according to the Marine Conservation Society’s 2007 data and a Surfers Against Sewage (SAS) report.
According to Charles Moore, these resin pellets account for around 8 percent of annual oil production and are the raw material for the 260 million tons of plastic consumed yearly worldwide. Lightweight and small, they escape in untold volumes during transport and manufacture and wash in the ocean.
Even though these researches have been conducted on nurdles, it is crucial to keep in mind, as Dr. Takada team confirmed, that other types of plastic debris (from fishing gear, shopping bags, to small fragments) displays the exact same propensity as the nurdles of raw plastic resin to absorb toxins.
Nurdles covered beach. Photo Source: Algalita Foundation
Plastic resin pellets are round, shiny and tiny, mostly less than 5mm in diameter. The very structure of the plastic material is oily and greasy (basically plastics are solid oil) therefore promoting the accumulation of hydrophobic contaminants (ones that tend to repel and not absorb water) from the surrounding seawater. Chemicals like PCB’s and DDE are very hydrophobic. It was shown that plastic pellets suck up these dangerous persistent organic pollutants (POPs) and toxins with a concentration factor that’s almost 1 million times greater compared to the overall concentration of the chemicals in seawater. In other words, waterborne hydrophobic pollutants do collect and magnify on the surface of plastic debris, thus making plastic far more deadly in the ocean than it would be on land.
These findings, published in the Marine Pollution Bulletin, were based on samples gathered from 30 beaches in 17 countries. PCB (Polychlorinated biphenyls) pollutant concentrations on plastic pellet were highest on US coasts, followed by Western Europe and Japan. The highest concentrations of DDT (Dichlorodiphenyltrichloroethane), the most toxic of all pesticides, were found on the US west coast and Vietnam.
Plastic marine debris, thought to be “indestructible”, “lasting forever”, has been shown to decompose faster than previously thought, under unexpected conditions (in the water and at sea temperature) and, most importantly, releasing toxic substances not found in the natural element: seawater.
DECOMPOSE
Since plastics belong to a chemical family of high polymers, they are essentially made up of a long chain of molecules containing repeated units of carbon atoms. Because of this inherent molecular stability (high molecular weight), plastics do not easily breakdown into simpler components.
North America, touched landscape. Photo Source: photobucket
Plastics do decompose, though not fully, over a very long period of time (in average 100 to 500 years). Commercially available plastics (polyolefins like polyethylene, polypropylene, etc.) have been further made resistant to decomposition by means of additional stabilizers like antioxidants. Thus, unless the plastic is specially designed to decompose in the soil, such materials can last a very long time because the chemical bonds that hold the molecules together are often stronger than nature’s power to take them apart. This means that soil microorganisms that can easily attack and decompose things like wood and other formerly living materials cannot break the various kinds of strong bonds that are common to most plastics. This depends upon the plastic (polymer) and the environment to which it is exposed.
The Marine Conservancy has published that the estimated decomposition rates of most plastic debris found on coasts are:
- Foamed plastic cups: 50 years
- Plastic beverage holder: 400 years
- Disposable diapers: 450 year
- Plastic bottle: 450
- Fishing line: 600 years.
Until Dr. Saido’s report, no studies had been conducted on plastic decomposition at low temperature in the marine environment, owing to the mistaken conception that plastic does practically not decompose in such condition. In the first study to look at what happens over the years to the billions of pounds of plastic waste drifting in the world’s oceans, researchers, lead by Katsuhiko Saido, PhD, reported that plastic does “decompose with surprising speed (as little as a year) and release potentially toxic substances into the water.”
These findings were reported on August 19, 2009, at the 238th National Meeting of the American Chemical Society (ACS). The scientists there termed the discovery “surprising.”
Dr. Saido described a new method to simulate the breakdown of plastic products at low temperatures (30º Celsius, 86º F), such as those found in some oceans. David Barnes, marine ecologist from the British Antarctic Survey, expressed that the Japanese’s team lab results cannot be applied uniformly across the ocean. However, even though the decomposition process would not occur in much cooler seawater as Barnes mentioned, the oceans are vast, currents are constant and permanent, nothing stays static and furthermore, it seems that garbage patches where plastics accumulate, are to be found in even greater dimension in the South Gyres, in the tropical and sub tropical zones with very warm waters. One of the researchers stated: “Even at 30 degrees Celsius, the plastic decomposes. In natural conditions, the tide comes in and sunlight heats the plastics [which increases decomposition].”
The type of plastic studied by Saido’s team was polystyrene, a white foamed plastic, commonly known by the trademark Styrofoam.
The process involved modeling plastic decomposition at room temperature, removing heat from the plastic and then using a liquid to extract the BPA and PS Oligomer that are not found naturally, thus must have been created through the decomposition of the plastic. Once degraded, the plastic was shown to release three new compounds not found in nature: styrene monomer (SM), styrene dimer (SD) and styrene trimer (ST). While SM is already a known carcinogen, SD and ST are suspected to be as well.
Plastics are not metabolized subsequent to ingestion since they are polymers. On the other hand, low molecular compounds such as PS oligomer or BPA from plastic decomposition are toxic and can be metabolized!
Samples of sea sand and seawater collected from Europe, India, Japan and the Pacific Ocean were found to be contaminated, with up to 150 parts per million of some of these components of plastic decomposition.
“Plastics in daily use are generally assumed to be quite stable,” said study lead researcher Katsuhiko Saido, Ph.D. “We found that plastic in the ocean actually decomposes as it is exposed to the rain and sun and other environmental conditions, giving rise to yet another source of global contamination that will continue into the future.”
This latest study clearly shows new micro-pollution by compounds generated by plastic decomposition to be taking place out of sight in the ocean, leaching toxic chemicals such as Bisphenol A (BPA) and derivatives of polystyrene.
Even though present in seawater and sands, the pollutants are found in highest concentration in areas heavily littered with plastic debris, such as ocean vortices, which bring us to define more specifically the notion of gyres and “garbage patches”.
David
