Andrey Nailor, M.D.·Published 25 January 2013·11 min read
Key points
Plastics have transformed modern society, providing attractive benefits but also befouling waterways and aquifers, depleting petroleum supplies and disrupting human health.
As Halden explains, the problems posed by plastics need to be addressed on several fronts, and current research offers significant hope for improvements to human and environmental health.
Common uses: 2 liter soda bottles, cooking oil bottles, peanut butter jars.
Common uses: detergent bottles, milk jugs, grocery bags.
Plastics have transformed modern society, providing attractive benefits but also befouling waterways and aquifers, depleting petroleum supplies and disrupting human health.
Rolf Halden, a researcher at Arizona State University’s Biodesign Institute has been following the chemical trail of plastics, quantifying their impact on human health and the environment. In a new overview appearing in the journal Reviews on Environmental Health, Halden and his co-author, ASU student Emily North, detail the risks and societal rewards of plastics and describe strategies to mitigate their negative impacts, through reconsideration of plastic composition, use and disposal.
“We are in need of a second plastic revolution. The first one brought us the age of plastics, changing human society and enabling the birth and explosive growth of many industries. But the materials used to make plastics weren’t chosen judiciously and we see the adverse consequences in widespread environmental pollution and unnecessary human exposure to harmful substances. Smart plastics of the future will be equally versatile but also non-toxic, biodegradable and made from renewable energy sources,” says Halden.
Plastics are made up of a network of molecular monomers linked to form macromolecules. These versatile chemical structures come in enormous varieties and today over 20 major forms of plastics exist. Plastics are typically lightweight and biocompatible. Along with their myriad uses in everyday life, plastics fulfill many needs in the public health arena, where they are found in items including absorbable sutures, prosthetics and engineered tissues.
Further, plastics may be manufactured at low cost using little energy and their adaptable composition allows them to be synthesized in soft, transparent or flexible forms suitable for a broad range of medical applications. Because they can be readily disposed of, items like latex gloves, dialysis tubes, intravenous bags and plastic syringes eliminate the need for repeated sterilization, which is often costly and inefficient. Such single-use items have had a marked effect on reducing blood-borne infections, including hepatitis B and HIV.
Many consumer products, such as water bottles and product containers, are made from various types of plastic. The Society of the Plastics Industry (SPI) established a classification system in 1988 to allow consumers and recyclers to properly recycle and dispose of different types of plastic. Manufacturers follow a coding system and place an SPI code, or number, on each plastic product, which is usually molded into the bottom. Although you should always verify the plastic classification number of each product you use, this guide provides a basic outline of the different plastic types associated with each code number.
Plastic marked with an SPI code of 1 is made with Polyethylene Terephthalate, which is also known as PETE or PET. Containers made from this plastic sometimes absorb odors and flavors from foods and drinks that are stored in them. Items made from this plastic are commonly recycled. PETE plastic is used to make many common household items like beverage bottles, medicine jars, peanut butter jars, combs, bean bags, and rope. Recycled PETE is used to make tote bags, carpet, fiberfill material in winter clothing, and more.
Written and revised by
Andrey Nailor, M.D.
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Plastic marked with an SPI code of 2 is made with High-Density Polyethylene, or HDPE. HDPE products are very safe and they are not known to transmit any chemicals into foods or drinks. HDPE products are commonly recycled. Items made from this plastic include containers for milk, motor oil, shampoos and conditioners, soap bottles, detergents, and bleaches. Many personalized toys are made from this plastic as well. (Please note: it is NEVER safe to reuse an HDPE bottle as a food or drink container if it didn’t originally contain food or drink!) Recycled HDPE is used to make plastic crates, plastic lumber, fencing, and more.
Plastic labeled with an SPI code of 3 is made with Polyvinyl Chloride, or PVC. PVC is not often recycled and it can be harmful if ingested. PVC is used for all kinds of pipes and tiles, but it's most commonly found in plumbing pipes. This kind of plastic should not come in contact with food items. Recycled PVC is used to make flooring, mobile home skirting, and more.
Plastic marked with an SPI code of 4 is made with Low-Density Polyethylene, or LDPE. LDPE is not commonly recycled, but it is recyclable in certain areas. It is a very healthy plastic that tends to be both durable and flexible. Plastic cling wrap, sandwich bags, squeezable bottles, and plastic grocery bags are all made from LDPE. Recycled LDPE is used to make garbage cans, lumber, furniture, and more.
Plastic marked with an SPI code of 5 is made with Polypropylene, or PP. PP is not commonly recycled, but it is accepted in many areas. This type of plastic is strong and can usually withstand higher temperatures. Among many other products, it is used to make plastic diapers, Tupperware, margarine containers, yogurt boxes, syrup bottles, prescription bottles, and some stadium cups. Plastic bottle caps are often made from PP as well. Recycled PP is used to make ice scrapers, rakes, battery cables, and more.
Plastic marked with an SPI code of 6 is made with Polystyrene, also known as PS and most commonly known as Styrofoam. It is commonly recycled, but it is difficult to do so and often ends up in landfills anyway. Disposable coffee cups, plastic food boxes, plastic cutlery, packing foam, and packing peanuts are made from PS. Recycled PS is used to make insulation, license plate frames, rulers, and more.
The SPI code of 7 is used to designate miscellaneous types of plastic that are not defined by the other six codes. Polycarbonate and Polylactide are included in this category. These types of plastics are difficult to recycle. Polycarbonate, or PC, is used in baby bottles, large water bottles (multiple-gallon capacity), compact discs, and medical storage containers. Recycled plastics in this category are used to make plastic lumber, among other products.
Consumers can make better plastic-purchasing decisions if they understand SPI codes and potential health hazards of each plastic, and recyclers can more effectively separate plastics into categories. Always check a product’s classification code prior to recycling it or re-using it. It’s important to stay educated about plastic classification numbers and plastic types; remember, informed consumers can demand that plastics manufacturers provide better products.
Many varieties of polymers are produced to meet the expanding needs of modern medicine. Polymer chemistry is used to produce sophisticated drug delivery systems for the pharmaceutical industry; material to cement bone for hip replacements is made with polymer polymethylmethacrylate and polymer scaffolds are revolutionizing the practice of tissue engineering.
Researchers like Halden have shown, however, that the benefits of global plastics use can come at a steep price in terms of both human and environmental health. Continuous contact with plastic products, from the beginning to the end of life has caused chemical ingredients - some with potentially harmful effects - to form steady-state concentrations in the human body.
In recent years, two plastic-associated compounds have been singled out for particular scrutiny, due to their endocrine-disrupting properties: Bisphenol A (BPA) and di-(2-ethylhexyl)phthalate (DEHP). Studies of bioaccumulation have shown that detectable levels of BPA in urine have been identified in 95 percent of the adult population in the U.S. and both BPA and DEHP have been associated, through epidemiological and animal studies, with adverse effects on health and reproduction. These include early sexual maturation, decreased male fertility, aggressive behavior and other effects. Concern over BPA exposure, particularly for highly vulnerable members of the population, has recently led the Food and Drug Administration to place a ban on BPA use in infant bottles, spill proof cups and other products intended for infants and toddlers.
Similar issues exist with DEHP, a plasticizer found in polyvinyl chloride (PVC). Because this additive is not tightly bound to the plastics in which it is used, the potential exists for DEHP to leach out and enter the body, causing unwanted exposure and affecting health. Both animal and human studies suggest DEHP may produce harmful effects, including insulin resistance, increased waist circumference and changes to male and female reproductive systems.
A variety of other plastic-related chemicals are currently under evaluation by Halden’s group for their adverse effects on health and the environment. These include polyhalogenated flame retardants, polyfluorinated compounds and antimicrobials containing plastic additives such as triclosan and triclocarban.
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While researchers are still at the early stages of assessing the risks to human health posed by plastics use, negative impacts on the environment have been a growing concern for many years. Over 300 million metric tons of plastics are produced worldwide each year. Roughly 50 percent of this volume is made up of products disposed of within one year of purchase.
Plastics today represent 15-25 percent of all hospital waste in the U.S. Some newer plastics are biodegradeable, but the rest must be incinerated, disposed of in landfills, or recycled. All of these methods have drawbacks and carry environmental risk, as the new study explains.
Biodegradeable plastics may break down in the environment into smaller polymer constituents, which may still pose a risk to the environment. Incineration liberates greenhouse gases associated with climate change. Landfilling of plastics, particularly in the enormous volumes now produced, may be an impractical use of land resources and a danger exists of plastics constituents entering the ground water. Finally, recycling of plastics requires careful sorting of plastic material, which is difficult. Recycled plastics tend to be of lower quality and may not be practical for health care and other applications.
Infographic on dangers of plastics
As Halden explains, the problems posed by plastics need to be addressed on several fronts, and current research offers significant hope for improvements to human and environmental health. Better biodegradeable plastics are now being developed using carbon dioxide and carbon monoxide compounds and applying metal complexes as catalysts.
Plastic recycling can be very confusing. One way to think about the different types of plastic is to compare plastic to fruit. Not all fruit is the same. An apple is not an orange. Not all plastic is the same. Plastic #1 is not plastic #5. Even within the same plastic group there are differences. Consider apples. A red apple is not a green apple. A plastic #2 narrow neck milk jug is not the same as a plastic #2 wide mouth yogurt cup. Keep the value of plastic high by placing only those types that are accepted for recycling in your recycling container. There are many types of plastic in use. Plastic must be sorted by type for recycling since each type melts at a different temperature and has different properties. The plastics industry has developed an identification system to label different types of plastic. The system divides plastic into seven distinct groups and uses a number code generally found on the bottom of containers. The following table explains the seven code system.
Plastic #1: Polyethylene Terephthalate
Common uses: 2 liter soda bottles, cooking oil bottles, peanut butter jars. This is the most widely recycled plastic and the only one with redemption value under the California "Bottle Bill." Many recycling programs and centers request that you remove caps and flatten the bottles.
Plastic #2: High Density Polytheylene
Common uses: detergent bottles, milk jugs, grocery bags. Most curbside recycling programs accept rigid narrow neck containers. Contact your curbside recycling service provider about whether they take plastic #2 and if containers need to be sorted by color.
Plastic #3: Polyvinyl Chloride
Common uses: plastic pipes, outdoor furniture, shrink wrap, water bottles, salad dressing and liquid detergent containers. Recycling centers rarely take #3 plastic. Look for alternatives whenever possible.
Plastic #4: Low Density Polyethylene
Common uses: dry cleaning bags, produce bags, trash can liners, food storage containers. Recycling centers rarely take #4 plastic. Look for alternatives whenever possible.
Plastic #5: Polypropylene
Common uses: aerosol caps, drinking straws Recycling centers rarely take #5 plastic. Look for alternatives whenever possible.
The technique provides a double benefit, binding unwanted greenhouse gases, while avoiding the competition with the human food supply. (Conventional bioplastics are made with plant sources like corn and molasses.) One application would be to replace BPA-containing epoxy resins lining metal food cans, thereby dramatically reducing BPA exposure while also sequestering 180 million metric tons of carbon dioxide (greenhouse) emissions.
The use of disposable items is also undergoing a reevaluation, in light of the potential environmental toll. In some cases, reusable plastic products are gaining ground, and estimates suggest the potential for a 50 percent reduction in medical equipment costs. Almost a quarter of all U.S. hospitals are now using reprocessing to decrease disposable waste.
Nevertheless, the largest source of plastics-related environmental damage stems from the overuse of items whose long-term harm outweighs their short-term benefit. Typically, these are consumer convenience items, often quickly discarded after a short use-life, including plastic water bottles, grocery bags, packaging, Styrofoam cups, Teflon-coated dental floss and other products. Halden recommends a thorough life-cycle assessment of plastics-based products, to identify safer, more sustainable replacement materials that reduce adverse effects to the environment and human health from plastic consumption.
“Many current types and consumption patterns of plastics are unsusustainable, as indicated by harmful plastic components circulating in our blood streams and multiple giant garbage patches of plastic debris swirling in the world’s oceans. Continued use of plastics into the future will require us to redesign these indispensible materials of daily life to make them compatible with human health and the ecosystems we rely on,” says Halden.
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Rolf Halden has been appointed to lead a new effort to protect human health and critical ecosystems, called the Center for Environmental Security (CES) at Ariziona State University. The goal of the Center is to protect human populations and the planet by detecting, minimizing and ultimately eliminating harmful chemical and biological agents through engineering interventions.
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Additionally, Halden is a professor in the Ira A. Fulton Schools of Engineering, School of Sustainable Engineering and the Built Environment, Co-Director of the Center for Health Information Research and Senior Sustainability Scientist at ASU's Global Institute of Sustainability
Written by: Richard Harth Science Writer: The Biodesign Institute richard.harth@asu.edu
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