The Background

Plastics consist of polymers or long molecules repeated over and over again, forming a long bonded chain. To a chemist, plastics fall into this category of polymers but so do proteins like hair or nails, rubber, breast implants, DNA and cellulose in hemp and wood, among others. The shape of the polymer gives the plastics their flexibility and malleability. Mankind has used plastics for centuries; however, these plastics were derived from natural materials like keratin, rubber, and cellulose. The plastics we know as today’s plastics are primarily made up of carbon, which is normally derived from fossil fuels and in particular from petroleum-based carbon like crude oil.

The major breakthrough in modern-day commercial plastics came in 1907 and was developed by a Belgian-born American named Leo Baekeland. Baekeland used coal tar to create phenol, which he developed into the very first synthetically derived plastic. Baekeland used the plastic within radio and telephone casings and electrical insulators. It was a major breakthrough in technology because of its non-conductive and heat-resistant properties. Baekeland’s technology progressed the synthetic plastic industry rapidly. By the beginning of the 1930s manufacturers created polystyrene (Styrofoam), then polyester, polyvinylchloride (PVC—i.e. piping), polythene and nylon, all within a 6-year span (a). Six years later, DuPont engineer Nathaniel Wyeth invented polyethylene terephthalate (PET) aka plastic bottles. All of these innovations caused petrochemical companies to invest in facilities to process their extracted crude oil into plasticizers. In addition, the shortfall in rubber materials during WWII created rapid research and development of petroleum-based plastics. This led to further investments into the industry alongside the development and demand for different plastic materials.

After WWII, a surplus of plastic inventory caused companies to pivot their market. The target market was no longer industry and government but instead the direct consumer themselves- a new and untouched mass market- the everyday American household. In 1948 Earl Tupper released Tupperware branded products and fostered the growth of his products by having women host Tupperware Parties in an effort to empower new workforce women to build markets by spurring demand. Petrochemical companies further developed plastics creating polypropylene (PP—i.e. plastic bottle caps) and high-density polyethylene (HDPE – i.e. milk cartons). By 1978 developers created low-density polyethylene (LDPE – i.e. plastic bags). Increased demand for these easy-to-use materials created mass production, which reduced costs making petro-based plastics more competitive than naturally-derived plastics. As Americans became more accustomed to one-use plastic, demand grew evermore and spread across the world. Now we live in a petroleum-based plastic world and as convenient as it is, the repercussions are everlasting.

The Problems

We have a plastic pollution problem! Petroleum-based plastics have a tremendous impact on our environment and human health. Not only in the use phase, but through the entire life cycle, from raw material to disposal. Let’s start at the raw material. The raw material, or feedstock, of petroleum-based plastic is often crude oil or natural gas. If the feedstock is not crude oil or natural gas then the feedstock must be upgraded. All of processes are associated with energy-intensive processes that demand inputs like water, heavy machinery, chemical processes and the like.

Plastic Processing — From Oil to Nurdle

Once a petroleum refinery acquires crude oil or natural gas, the feedstock must go through a series of energy-intensive refining stages. Refining separates the oils into different markets like gasoline, diesel, propane, chemicals or plastics. (c) The refined petroleum for plastic markets is then processed into polymers, which are often shaped into tiny plastics pellets that are shipped to injection molding facilities all over the world.

After polymerization, the polymers are mixed with other additives and plasticizers in a process called compounding. Hoppers feed the blends of polymers/copolymers with additives like anti-oxidants, UV-stabilizers, plasticizers, fiberglass and other agents. These are blended at a molten state requiring significant energy inputs (d). Extrusion compounding is one of the more commonly used methods; it resembles a massive screw, which transports the material down a pipeline towards the coloring agent. The material exits the extrusion compounder in the form of long plastic strands. These are then cooled in a water bath or sprayed on a conveyor belt, requiring a large quantity of fresh water and energy in order to keep the water cool. The conveyor moves the strands into a granulator where they are chopped into small pellets, commonly called ‘Nurdles‘. These Nurdles are then bagged and transported to the injection molding facility.

These Nurdles normally arrive at the intended location, but they are so small, sometimes they end up in waterways like rivers, lakes, and oceans only to suspend in the water column or wash up on shore. Here they are accidentally eaten by aquatic species or are washed up onto a beach where they are eaten by birds.

plastic pellets - Plastic pollution problem

Plastic pollution pieces picked up on a beach on Lake Michigan. The clear plastic bits in the red box are plastic Nurdles that were polluted before they reached the final manufacturing stage.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Plastic Processing — From Nurdle to Product

When the Nurdles, or plastic pellets, arrive at the injection molding facilities, the facilities contain molds of whatever the facility fabricates. The molds are massive robotic units that can operate 24/7 depending on industry needs. Employees dump the plastic Nurdles into the molds. The molds operate at high temperatures in order for the Nurdles to melt. For the most commonly used plastics, molding temperatures must heat above 248 degrees Fahrenheit (e).  Molds consist of “male” and “female” parts that fit together. The mold closes and tubes push the now liquid Nurdles into the mold. Water then rushes through tubings (usually closed-loop systems) and quickly cools the plastic, hardening the mold. Look at the bottom of a plastic bottle or container and find a small ridge that protrudes over the rest of the smooth surface. That is the point of injection.

While injection molding is a fairly quick and efficient process, there is a lot of waste that comes with injection molding. Depending on the facility, this waste either thrown into a landfill is shredded and recycled; however, it will never be the same quality. Recycled plastic is always a reduced quality of its previous plastic grade. In addition, while the injection molding process is efficient, the efficiency propels the supply of plastics and allows the supply for the quick turnaround of single-use plastics into the consumer’s supply chain.

After the molding process, the plastic material is removed from the mold, packaged (in more plastic and cardboard) and shipped to a distributor where it sits in a warehouse until the buyer requests it. In an example of a single-use plastic, like a straw, boxes of several thousand straws are shipped to a restaurant or convenience store. The employee unpacks the straws and puts them on a shelf or in a container for the end user. If at a restaurant, the end user asks the employee for a drink. The employee fills the glass and puts the straw in the drink to give to the consumer. The consumer then drinks it. When finished, the consumer (or server) tosses the straw into the trash for its final stage or “processing.” While some plastics can be recycled, straws cannot. So that straw and other plastics must go to a landfill where they will remain for the foreseeable future.

Plastics End of Life — its basically eternity

Petroleum-based plastics do not rapidly biodegrade like naturally derived plastics and the chemical inputs that make up the plastics leach into the grounds and waterways. Only limited plastics are recycled because the value of the recycled plastic is quite low. If the plastics are not thrown into a landfill or recycled, the plastic floats into waterways and washes up on shores or flows out into our oceans. When the plastic washes up on beaches, birds often eat the plastic thinking that it is food. Birds cannot digest the plastic, so the plastic stays in their bodies until they die.

Broken Plastic - Plastic pollution problem

Plastic pieces that have slowly begun to break apart in water.

The plastics that hit our oceans are pushed through jet streams into giant gyres or garbage patches. The larger pieces, particularly plastic bags, can mimic jellyfish. Sea turtles oftentimes believe these bags are jellyfish and will eat them. Since the turtle cannot digest the plastic, the turtle thinks it is full and ends up starving to death. It is not just big pieces of plastics either. Some are large pieces, but most of the plastics found in the oceans are micro-plastics.

Micro-plastics are tiny pieces of plastic that have broken down in water. Plastic micro-beads are also found throughout the oceans. Micro-beads, like in exfoliants, are found in many consumer products for abrasion purposes.. Both micro-plastics and micro-beads suspend in the ocean water column. Like an iceberg, the gyres have plastics floating on top of the surface and underneath the surface. These gyres are in all five oceans and the Pacific Gyre is so large it expands the size of the continental United States!

 

Microplastics - Plastic pollution problem

Most of these plastic pieces are still too large to be considered micro-plastics; however, the pieces in the red boxes could be or almost could be considered micro-plastics.

Plankton, the basis of the ocean’s food chain, unknowingly eat the micro-plastics. Shrimp eat the plankton and the chemicals in the micro-plastic bio-accumulate in the shrimp. The shrimp are caught and then served to humans, which furthers the bio-accumulation of the chemicals in the micro-plastic. Not only do these micro-plastics cause problems in our oceans, in our aquatic species and through bio-accumulation in humans, micro-plastics and the gyres have created a home for a new ocean insect called the Halobate insect (f), which is preying on plankton, the basis of our oceanic food-chain. Without plankton, the oceans suffer. If the oceans suffer- life suffers.

Other plastic problems — BPA and other inputs

In addition, plastics can contain harmful chemicals that have unknown impacts on human health. Instead, companies view them as safe until they realize the long-term effects on humans. We are test-subjects.  Remember BPA? BPA (Bisphenol A) is a synthetic compound used in cans, food storage containers and plastic beverage containers like water bottles. While the FDA still maintains the belief that BPA is safe at low levels occurring in foods, they are still conducting research on the product. Research has shown that BPA found in plastic and canned containers could seep into foods and cause negative health problems with brain, behavior, and prostate glands of fetuses, infants and children. Research also has linked BPA with increased blood pressure (g).  In an effort to protect themselves, manufacturers have started to create BPA free-products, but not all plastics are BPA-free. They also are not free from other potentially carcinogenic substances of which a realized problem is not yet known because the product has not been used long enough to know the long-term effects on human health.

In sum, all the plastic that has ever been made is still present today. Plastics require significant inputs in resources, energy, water, and chemicals before they even hit the consumer. For single-use plastic, the consumer might use it for less than 24 hours and then dispose of it, and, if it isn’t recycled, it will either sit in a landfill for thousands of years or it will eventually breakdown in our oceans and feed back into human bodies in the form of bio-accumulation.

Kind of disturbing, right? We think so too.

The Solution

As companies and the general public become more aware of this potentially harmful and serious, natural-based plastics are re-emerging. Corn and potato-based compostable plastics (which can also be made from hemp!) are hitting markets. These are compostable in industrial scale composting environments. In the right conditions, compostable plastics can decompose within 90-180 days. This is far better than the tens of thousands of years it takes for petroleum-based plastics.

Other companies are innovating equipment that actually collect the plastics in the oceans and turn the plastic back into oil! While other organizations, like the Plastic Pollution Coalition, are working to educate the general public on the issue.

We know the problem seems difficult to overcome but if we all work as one, we can stop this disgusting chain of consumption!

So what can everyday citizens do? Educate yourself, your friends, your family and total strangers.

RECYCLE! That recycle triangle at the bottoms of plastics does not mean it’s recyclable. It actually is there to inform the consumer of the type of plastic used in the product. Get to know your city’s recycling schedule. Not all cities recycle all plastics, but most cities recycle #1 and #2.

Description and meanings of plastic numbers within triangles - Plastic pollution problem

REDUCE plastic consumption, in particular, single-use plastic consumption! Buy compostable plastics. But don’t just buy them and throw them in your trash for landfill. Give them to the city composting facility (if available) so that they can decompose under proper conditions.

If given a single-use plastic product, REUSE it as many times as possible, or recycle it, if possible.

However ultimately, the best solution is to REFUSE plastic altogether! Buy reusable cutlery, reusable straws, reusable bags, and reusable water bottles. And when out with friends at a restaurant say, “No straw please!”

How Can Hemp Help?

Industrial hemp oil can be used to make bioplastics, similar to corn and soy. These bioplastics can degrade within 180 days in an industrial composter.

Hemp fibers can also be used to create bioplastics like thermosets used in automobiles. These wouldn’t always biodegrade but their environmental impact during manufacturing outperforms petroleum-grade plastics!

 

 

(a) Knight, L. A brief history of plastics, natural and synthetic. BBC News. 17 May 2014.  http://www.bbc.com/news/magazine-27442625

(b) The Plastics Industry Trade Association. History of Plastics. Washington, D.C. https://www.plasticsindustry.org/AboutPlastics/content.cfm?ItemNumber=670

(c) U.S. Energy Information Administration. Refining Crude Oil. 16 Jun 2016.  http://www.eia.gov/energyexplained/index.cfm?page=oil_refining

(d) WiseGeek. What is plastic compounding? Conjecture Corporation. 2016. http://www.wisegeek.com/what-is-plastic-compounding.htm

(e) Todd, Robert H.; Allen, Dell K.; Alting, Leo (1994). Manufacturing Processes Reference Guide. Industrial Press, Inc.

(f) Welsh, J. Ocean Garbage Patch Breeds Bugs. Live Science. 8 May 2012.  http://www.livescience.com/20183-plastic-ocean-insect-breeding.html

(g) Mayo Clinic. What is BPA, and what are the concerns of BPA? Nutrition and Healthy Eating. 2016. http://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/expert-answers/bpa/faq-20058331

The Background

Plastics consist of polymers or long molecules repeated over and over again, forming a long bonded chain. To a chemist, plastics fall into this category of polymers but so do proteins like hair or nails, rubber, breast implants, DNA and cellulose in hemp and wood, among others. The shape of the polymer gives the plastics their flexibility and malleability. Mankind has used plastics for centuries; however, these plastics were derived from natural materials like keratin, rubber, and cellulose. The plastics we know as today’s plastics are primarily made up of carbon, which is normally derived from fossil fuels and in particular from petroleum-based carbon like crude oil.

The major breakthrough in modern-day commercial plastics came in 1907 and was developed by a Belgian-born American named Leo Baekeland. Baekeland used coal tar to create phenol, which he developed into the very first synthetically derived plastic. Baekeland used the plastic within radio and telephone casings and electrical insulators. It was a major breakthrough in technology because of its non-conductive and heat-resistant properties. Baekeland’s technology progressed the synthetic plastic industry rapidly. By the beginning of the 1930s manufacturers created polystyrene (Styrofoam), then polyester, polyvinylchloride (PVC—i.e. piping), polythene and nylon, all within a 6-year span (a). Six years later, DuPont engineer Nathaniel Wyeth invented polyethylene terephthalate (PET) aka plastic bottles. All of these innovations caused petrochemical companies to invest in facilities to process their extracted crude oil into plasticizers. In addition, the shortfall in rubber materials during WWII created rapid research and development of petroleum-based plastics. This led to further investments into the industry alongside the development and demand for different plastic materials.

After WWII, a surplus of plastic inventory caused companies to pivot their market. The target market was no longer industry and government but instead the direct consumer themselves- a new and untouched mass market- the everyday American household. In 1948 Earl Tupper released Tupperware branded products and fostered the growth of his products by having women host Tupperware Parties in an effort to empower new workforce women to build markets by spurring demand. Petrochemical companies further developed plastics creating polypropylene (PP—i.e. plastic bottle caps) and high-density polyethylene (HDPE – i.e. milk cartons). By 1978 developers created low-density polyethylene (LDPE – i.e. plastic bags). Increased demand for these easy-to-use materials created mass production, which reduced costs making petro-based plastics more competitive than naturally-derived plastics. As Americans became more accustomed to one-use plastic, demand grew evermore and spread across the world. Now we live in a petroleum-based plastic world and as convenient as it is, the repercussions are everlasting.

The Problems

We have a plastic pollution problem! Petroleum-based plastics have a tremendous impact on our environment and human health. Not only in the use phase, but through the entire life cycle, from raw material to disposal. Let’s start at the raw material. The raw material, or feedstock, of petroleum-based plastic is often crude oil or natural gas. If the feedstock is not crude oil or natural gas then the feedstock must be upgraded. All of processes are associated with energy-intensive processes that demand inputs like water, heavy machinery, chemical processes and the like.

Plastic Processing — From Oil to Nurdle

Once a petroleum refinery acquires crude oil or natural gas, the feedstock must go through a series of energy-intensive refining stages. Refining separates the oils into different markets like gasoline, diesel, propane, chemicals or plastics. (c) The refined petroleum for plastic markets is then processed into polymers, which are often shaped into tiny plastics pellets that are shipped to injection molding facilities all over the world.

After polymerization, the polymers are mixed with other additives and plasticizers in a process called compounding. Hoppers feed the blends of polymers/copolymers with additives like anti-oxidants, UV-stabilizers, plasticizers, fiberglass and other agents. These are blended at a molten state requiring significant energy inputs (d). Extrusion compounding is one of the more commonly used methods; it resembles a massive screw, which transports the material down a pipeline towards the coloring agent. The material exits the extrusion compounder in the form of long plastic strands. These are then cooled in a water bath or sprayed on a conveyor belt, requiring a large quantity of fresh water and energy in order to keep the water cool. The conveyor moves the strands into a granulator where they are chopped into small pellets, commonly called ‘Nurdles‘. These Nurdles are then bagged and transported to the injection molding facility.

These Nurdles normally arrive at the intended location, but they are so small, sometimes they end up in waterways like rivers, lakes, and oceans only to suspend in the water column or wash up on shore. Here they are accidentally eaten by aquatic species or are washed up onto a beach where they are eaten by birds.

plastic pellets - Plastic pollution problem

Plastic pollution pieces picked up on a beach on Lake Michigan. The clear plastic bits in the red box are plastic Nurdles that were polluted before they reached the final manufacturing stage.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Plastic Processing — From Nurdle to Product

When the Nurdles, or plastic pellets, arrive at the injection molding facilities, the facilities contain molds of whatever the facility fabricates. The molds are massive robotic units that can operate 24/7 depending on industry needs. Employees dump the plastic Nurdles into the molds. The molds operate at high temperatures in order for the Nurdles to melt. For the most commonly used plastics, molding temperatures must heat above 248 degrees Fahrenheit (e).  Molds consist of “male” and “female” parts that fit together. The mold closes and tubes push the now liquid Nurdles into the mold. Water then rushes through tubings (usually closed-loop systems) and quickly cools the plastic, hardening the mold. Look at the bottom of a plastic bottle or container and find a small ridge that protrudes over the rest of the smooth surface. That is the point of injection.

While injection molding is a fairly quick and efficient process, there is a lot of waste that comes with injection molding. Depending on the facility, this waste either thrown into a landfill is shredded and recycled; however, it will never be the same quality. Recycled plastic is always a reduced quality of its previous plastic grade. In addition, while the injection molding process is efficient, the efficiency propels the supply of plastics and allows the supply for the quick turnaround of single-use plastics into the consumer’s supply chain.

After the molding process, the plastic material is removed from the mold, packaged (in more plastic and cardboard) and shipped to a distributor where it sits in a warehouse until the buyer requests it. In an example of a single-use plastic, like a straw, boxes of several thousand straws are shipped to a restaurant or convenience store. The employee unpacks the straws and puts them on a shelf or in a container for the end user. If at a restaurant, the end user asks the employee for a drink. The employee fills the glass and puts the straw in the drink to give to the consumer. The consumer then drinks it. When finished, the consumer (or server) tosses the straw into the trash for its final stage or “processing.” While some plastics can be recycled, straws cannot. So that straw and other plastics must go to a landfill where they will remain for the foreseeable future.

Plastics End of Life — its basically eternity

Petroleum-based plastics do not rapidly biodegrade like naturally derived plastics and the chemical inputs that make up the plastics leach into the grounds and waterways. Only limited plastics are recycled because the value of the recycled plastic is quite low. If the plastics are not thrown into a landfill or recycled, the plastic floats into waterways and washes up on shores or flows out into our oceans. When the plastic washes up on beaches, birds often eat the plastic thinking that it is food. Birds cannot digest the plastic, so the plastic stays in their bodies until they die.

Broken Plastic - Plastic pollution problem

Plastic pieces that have slowly begun to break apart in water.

The plastics that hit our oceans are pushed through jet streams into giant gyres or garbage patches. The larger pieces, particularly plastic bags, can mimic jellyfish. Sea turtles oftentimes believe these bags are jellyfish and will eat them. Since the turtle cannot digest the plastic, the turtle thinks it is full and ends up starving to death. It is not just big pieces of plastics either. Some are large pieces, but most of the plastics found in the oceans are micro-plastics.

Micro-plastics are tiny pieces of plastic that have broken down in water. Plastic micro-beads are also found throughout the oceans. Micro-beads, like in exfoliants, are found in many consumer products for abrasion purposes.. Both micro-plastics and micro-beads suspend in the ocean water column. Like an iceberg, the gyres have plastics floating on top of the surface and underneath the surface. These gyres are in all five oceans and the Pacific Gyre is so large it expands the size of the continental United States!

 

Microplastics - Plastic pollution problem

Most of these plastic pieces are still too large to be considered micro-plastics; however, the pieces in the red boxes could be or almost could be considered micro-plastics.

Plankton, the basis of the ocean’s food chain, unknowingly eat the micro-plastics. Shrimp eat the plankton and the chemicals in the micro-plastic bio-accumulate in the shrimp. The shrimp are caught and then served to humans, which furthers the bio-accumulation of the chemicals in the micro-plastic. Not only do these micro-plastics cause problems in our oceans, in our aquatic species and through bio-accumulation in humans, micro-plastics and the gyres have created a home for a new ocean insect called the Halobate insect (f), which is preying on plankton, the basis of our oceanic food-chain. Without plankton, the oceans suffer. If the oceans suffer- life suffers.

Other plastic problems — BPA and other inputs

In addition, plastics can contain harmful chemicals that have unknown impacts on human health. Instead, companies view them as safe until they realize the long-term effects on humans. We are test-subjects.  Remember BPA? BPA (Bisphenol A) is a synthetic compound used in cans, food storage containers and plastic beverage containers like water bottles. While the FDA still maintains the belief that BPA is safe at low levels occurring in foods, they are still conducting research on the product. Research has shown that BPA found in plastic and canned containers could seep into foods and cause negative health problems with brain, behavior, and prostate glands of fetuses, infants and children. Research also has linked BPA with increased blood pressure (g).  In an effort to protect themselves, manufacturers have started to create BPA free-products, but not all plastics are BPA-free. They also are not free from other potentially carcinogenic substances of which a realized problem is not yet known because the product has not been used long enough to know the long-term effects on human health.

In sum, all the plastic that has ever been made is still present today. Plastics require significant inputs in resources, energy, water, and chemicals before they even hit the consumer. For single-use plastic, the consumer might use it for less than 24 hours and then dispose of it, and, if it isn’t recycled, it will either sit in a landfill for thousands of years or it will eventually breakdown in our oceans and feed back into human bodies in the form of bio-accumulation.

Kind of disturbing, right? We think so too.

The Solution

As companies and the general public become more aware of this potentially harmful and serious, natural-based plastics are re-emerging. Corn and potato-based compostable plastics (which can also be made from hemp!) are hitting markets. These are compostable in industrial scale composting environments. In the right conditions, compostable plastics can decompose within 90-180 days. This is far better than the tens of thousands of years it takes for petroleum-based plastics.

Other companies are innovating equipment that actually collect the plastics in the oceans and turn the plastic back into oil! While other organizations, like the Plastic Pollution Coalition, are working to educate the general public on the issue.

We know the problem seems difficult to overcome but if we all work as one, we can stop this disgusting chain of consumption!

So what can everyday citizens do? Educate yourself, your friends, your family and total strangers.

RECYCLE! That recycle triangle at the bottoms of plastics does not mean it’s recyclable. It actually is there to inform the consumer of the type of plastic used in the product. Get to know your city’s recycling schedule. Not all cities recycle all plastics, but most cities recycle #1 and #2.

Description and meanings of plastic numbers within triangles - Plastic pollution problem

REDUCE plastic consumption, in particular, single-use plastic consumption! Buy compostable plastics. But don’t just buy them and throw them in your trash for landfill. Give them to the city composting facility (if available) so that they can decompose under proper conditions.

If given a single-use plastic product, REUSE it as many times as possible, or recycle it, if possible.

However ultimately, the best solution is to REFUSE plastic altogether! Buy reusable cutlery, reusable straws, reusable bags, and reusable water bottles. And when out with friends at a restaurant say, “No straw please!”

How Can Hemp Help?

Industrial hemp oil can be used to make bioplastics, similar to corn and soy. These bioplastics can degrade within 180 days in an industrial composter.

Hemp fibers can also be used to create bioplastics like thermosets used in automobiles. These wouldn’t always biodegrade but their environmental impact during manufacturing outperforms petroleum-grade plastics!

 

 

(a) Knight, L. A brief history of plastics, natural and synthetic. BBC News. 17 May 2014.  http://www.bbc.com/news/magazine-27442625

(b) The Plastics Industry Trade Association. History of Plastics. Washington, D.C. https://www.plasticsindustry.org/AboutPlastics/content.cfm?ItemNumber=670

(c) U.S. Energy Information Administration. Refining Crude Oil. 16 Jun 2016.  http://www.eia.gov/energyexplained/index.cfm?page=oil_refining

(d) WiseGeek. What is plastic compounding? Conjecture Corporation. 2016. http://www.wisegeek.com/what-is-plastic-compounding.htm

(e) Todd, Robert H.; Allen, Dell K.; Alting, Leo (1994). Manufacturing Processes Reference Guide. Industrial Press, Inc.

(f) Welsh, J. Ocean Garbage Patch Breeds Bugs. Live Science. 8 May 2012.  http://www.livescience.com/20183-plastic-ocean-insect-breeding.html

(g) Mayo Clinic. What is BPA, and what are the concerns of BPA? Nutrition and Healthy Eating. 2016. http://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/expert-answers/bpa/faq-20058331

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