I have been thinking about the manufacturing and recycling processes of plastics for a couple of years. I thought I knew a fair amount on the topic until a friend recently told me that he's working with a company that turns PET plastics (resin identification code 1) into yarn to make fabrics for goods such as backpacks. You may have already heard of this concept for making fleece fiber or tote bags. The kicker here is that my friend is integrating solar panels into this fabric - that's a different story though. We were wondering if any components from the PET would still be able to volatilize or evaporate from the final good, potentially posing any health concerns for consumers.
I have to admit that I have thought of this before, although I didn't have the skills to investigate the question. I previously worked at a LEED certified school where the carpets were made from 100% post consumer content PET recycled material. I always wondered if the children playing on the carpets, putting their hands in their mouths, breathing so close to the ground, etc. were experiencing any ingestion or inhalation of unseen bad chemical actors. Because many carpets made from recycled content use PET materials, I am going to attempt to answer both of these questions.
In order to start thinking about this, we need to describe PET, or polyethylene terephthalate. By the way, don't be confused by the "phthalate" in its name; the phthalates that are cause for concern have different chemical structures. If you can remember high school biology, I am sure you've heard that structure and function are closely related. So, PET is made from joining terephthalic acid with thylene glycol, using antimony as a catalyst. High heat and pressure are applied over some period of time to make the polymers 150 times longer. Copolymer blends can now be used and still retain PET labeling, according to the FDA. PET is assumed to be toxicant-free and safe for food and beverage containers; you will see the number 1 on the bottom of soda, water, and juice bottles, as well as condiment containers and trays you can put in the oven (like frozen dinners). However, many studies have shown various water bottle brands leach phthalates, as seen from bioassays that reveal varying degrees of estrogenic activity observed in mudsnails and yeast cultures. Additional studies show the measurements of phthalates leaching from water bottles vary according to temperature and length of time. But wait a minute, PET isn't made using phthalates! How did they get into water bottles? As of 2008, some new PET has been made from recycled PET, and although the recycling process begins with washing the containers, not all substances that have adsorbed onto the plastic are removed. Also, as previously mentioned, copolymers can be used in PET production, so there is variation in components of the manufacturing process. Researchers found different levels of phthalates, such as DMP, in soda bottles as compared to water bottles. "DMP [was found] in concentrations as high as 3,000 μg/L in PET-bottled soda, whereas they were unable to detect DMP at all in PET-bottled mineral water. One possible explanation is that the soda, perhaps because of its lower pH, promoted leaching of DMP from the PET bottle wall. However, it is also possible that the PET used in production of the bottles intended for soda had a different provenance than the PET used in production of the bottles intended for mineral water." So bringing this back to backpacks and carpets . . . well, maybe it's a good thing we don't drink out of them? And what about the children playing on the carpets and the people with backpacks on their skin? I think it's becoming clear how complicated this business of determining the safety of chemicals really is!
Phthalates are characterized by their lack of a covalent bond (remember those strong, electron-sharing bonds from chemistry) with the plastic compound they are mixed in. There are 26 common types of phthalates that differ by their chemical structure and volatility. A paper published from the Silent Spring Institute tells us that some phthalates, such as DEP, DMP, DBP are more likely to be found in indoor air, and higher temperatures lead to higher air concentrations of these compounds. DEHP and BBP, which are heavier and used in PVC materials, are more commonly found in dust. It has also been established that some phthalates are absorbed through the skin, as examined by studies conducted in the context of personal care products, many of which contain phthalates. I haven't yet found a satisfactory examination of dermally absorbed phthalates and the necessary amount that may affect human health, but I will continue looking and let you know what I find.
So in order to answer the question about backpacks and carpets made from PET, we would need to get a better look at the specific phthalates that may be present in these products. Because PET generally doesn't (or isn't supposed to) contain phthalates, my initial guess would be that most products made from PET would be safe. Also, we are not eating out of backpacks or carpets, and generally not rubbing them into our skin. However, if sufficient amounts of volatile or heavy phthalates were contaminants in the PET, there would be reason to look at the volatility and dust content of the recycled goods. I would also want to look at recycled content fleece fibers, such as those made by Patagonia. Because the market price for PET flakes (used for recycling) has more than doubled since 2007, we will continue to see an increase in PET products, and I would be surprised the safety of these recycled products doesn't continue to be examined. This is just the tip of the iceberg however. There are recycling numbers 2-7 as well! What is in those, and what is being made from those recycled products? I am sure you are anxious to know, but I will have to conduct another round of research and tell you about it another day!
I have to admit that I have thought of this before, although I didn't have the skills to investigate the question. I previously worked at a LEED certified school where the carpets were made from 100% post consumer content PET recycled material. I always wondered if the children playing on the carpets, putting their hands in their mouths, breathing so close to the ground, etc. were experiencing any ingestion or inhalation of unseen bad chemical actors. Because many carpets made from recycled content use PET materials, I am going to attempt to answer both of these questions.
In order to start thinking about this, we need to describe PET, or polyethylene terephthalate. By the way, don't be confused by the "phthalate" in its name; the phthalates that are cause for concern have different chemical structures. If you can remember high school biology, I am sure you've heard that structure and function are closely related. So, PET is made from joining terephthalic acid with thylene glycol, using antimony as a catalyst. High heat and pressure are applied over some period of time to make the polymers 150 times longer. Copolymer blends can now be used and still retain PET labeling, according to the FDA. PET is assumed to be toxicant-free and safe for food and beverage containers; you will see the number 1 on the bottom of soda, water, and juice bottles, as well as condiment containers and trays you can put in the oven (like frozen dinners). However, many studies have shown various water bottle brands leach phthalates, as seen from bioassays that reveal varying degrees of estrogenic activity observed in mudsnails and yeast cultures. Additional studies show the measurements of phthalates leaching from water bottles vary according to temperature and length of time. But wait a minute, PET isn't made using phthalates! How did they get into water bottles? As of 2008, some new PET has been made from recycled PET, and although the recycling process begins with washing the containers, not all substances that have adsorbed onto the plastic are removed. Also, as previously mentioned, copolymers can be used in PET production, so there is variation in components of the manufacturing process. Researchers found different levels of phthalates, such as DMP, in soda bottles as compared to water bottles. "DMP [was found] in concentrations as high as 3,000 μg/L in PET-bottled soda, whereas they were unable to detect DMP at all in PET-bottled mineral water. One possible explanation is that the soda, perhaps because of its lower pH, promoted leaching of DMP from the PET bottle wall. However, it is also possible that the PET used in production of the bottles intended for soda had a different provenance than the PET used in production of the bottles intended for mineral water." So bringing this back to backpacks and carpets . . . well, maybe it's a good thing we don't drink out of them? And what about the children playing on the carpets and the people with backpacks on their skin? I think it's becoming clear how complicated this business of determining the safety of chemicals really is!
Phthalates are characterized by their lack of a covalent bond (remember those strong, electron-sharing bonds from chemistry) with the plastic compound they are mixed in. There are 26 common types of phthalates that differ by their chemical structure and volatility. A paper published from the Silent Spring Institute tells us that some phthalates, such as DEP, DMP, DBP are more likely to be found in indoor air, and higher temperatures lead to higher air concentrations of these compounds. DEHP and BBP, which are heavier and used in PVC materials, are more commonly found in dust. It has also been established that some phthalates are absorbed through the skin, as examined by studies conducted in the context of personal care products, many of which contain phthalates. I haven't yet found a satisfactory examination of dermally absorbed phthalates and the necessary amount that may affect human health, but I will continue looking and let you know what I find.
So in order to answer the question about backpacks and carpets made from PET, we would need to get a better look at the specific phthalates that may be present in these products. Because PET generally doesn't (or isn't supposed to) contain phthalates, my initial guess would be that most products made from PET would be safe. Also, we are not eating out of backpacks or carpets, and generally not rubbing them into our skin. However, if sufficient amounts of volatile or heavy phthalates were contaminants in the PET, there would be reason to look at the volatility and dust content of the recycled goods. I would also want to look at recycled content fleece fibers, such as those made by Patagonia. Because the market price for PET flakes (used for recycling) has more than doubled since 2007, we will continue to see an increase in PET products, and I would be surprised the safety of these recycled products doesn't continue to be examined. This is just the tip of the iceberg however. There are recycling numbers 2-7 as well! What is in those, and what is being made from those recycled products? I am sure you are anxious to know, but I will have to conduct another round of research and tell you about it another day!
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