18
Jan
Researchers Raise Alarm about Ingested Nanoscale Microplastic Particles Not Previously Evaluated
(Beyond Pesticides, January 18, 2024) Research continues to raise alarms about the hazards associated with the use of plastic, including the microplastic particles that are distributed in alarming amounts throughout the environment and taken up by organisms, including humans. A study published by researchers at Columbia and Rutgers universities (see article in the Proceedings of the National Academy of Sciences, January 2024) reports that the average liter of three brands of bottled water in the U.S. contains almost a quarter of a million tiny plastic pieces, of which 90 percent are at the nanoscale. The other ten percent are slightly larger, at microscale. Last December, researchers at Norway’s MicroLEACH project published a study that analyzes the components of 50 items in common use—plastic bags, disposable cups, dishwashing gloves, car tire granules, children’s toys and balloons. (See summary.)
The researchers found, like in previous studies, that many hazardous chemicals in the plastics as well as many that could not be identified because they were not listed in the major chemical substance databases. Only 30 percent of the chemical compounds identified in the study were present in two or more products. This suggests that most plastics contain many unidentified chemicals, far beyond the known impurities, metabolites and degradation products. Further, it suggests that in the environment plastics are chemically reactive and forming new compounds no one has anticipated and whose toxicity is unknown.
Like pesticides, plastics—mostly derived from fossil fuels—are exerting a heavy drag on the health of ecosystems and human beings. An estimated 8,300 million metric tons have been created since plastic production skyrocketed during World War II. Annual global production of plastic has reached 400 million metric tons, according to one estimate, with some 13,000 chemicals used in their manufacture, of which only one percent is regulated. In a January report, Consumer Reports, in The Plastic Chemicals Hiding in Your Food, reports that, “Our tests of nearly 100 foods found that despite growing evidence of potential health threats, bisphenols and phthalates remain widespread in our food.†Key among the chemicals found in plastics are plasticizers (most commonly phthalates used to increase flexibility and softness) and bisphenols (including BPA used in can liners, bottle caps, and water bottles). Phthalates and BPA are endocrine disruptors, linked to developmental problems and cancer. In improving organic production and processing to address current use of plastic, Beyond Pesticides has called for an end to use of plastics in certified organic.
Recent concern has turned to microplastics, including those at nanoscale—measuring billionths of a meter, or 70 times smaller than the width of a human hair. Microplastics are tiny particles broken up and ground very fine by natural processes like friction and heat. Their small size enables easy travel in air and water. Nanoplastics are now distributed over the entire globe. They are found in sandy beaches and in ocean sediments, as fibers floating in the stratosphere, in bottled water, and in the tissues of living creatures. Whereas numerous adverse effects of fossil-derived pesticides and plastic exposures at the macroscale are relatively well known, very little research has focused on those of microplastics.
The rapid spread of macroscale plastic trash has been unintentional. But agricultural and pharmaceutical interests are also intentionally researching nanoscale materials, including plastics, as the next big thing in their respective technological revolutions. Development of nanomaterials to distribute pesticides and deliver drugs and other medical treatments is proceeding at breakneck pace with very little oversight or public awareness. Agricultural and medical innovators see mostly the wondrous applications nanomaterials promise, but seem unaware of the risks.
Most plastics are polymers—long chains of often identical or very similar smaller molecules called monomers. Humans naturally make a number of polymers, including collagen, DNA and fibrinogen. The molecular structure of a polymer makes it flexible and able to maintain structural integrity under mechanical stress. Synthetic polymers also have those qualities, which is why plastic is so popular. One medical review of nanomaterials described polymers optimistically as “biocompatible, biodegradable, non-toxic, and popular in medical applications such as drug delivery, wound plug dressings, stents, and tissue engineering.â€
Nanoplastics are attractive to pesticide proponents as a way to increase bioavailability, reduce product degradation, and increase water solubility. Timed release of the pesticide from the nanoparticle can be controlled, and some methods can make release contingent on exposure to light. These qualities are presented as advantages and purportedly reduce the amount of pesticide needed to control pests, helping the pesticide “exhibit extended pest control capabilities.â€
Of course, while pesticide volume may be reduced using nanoparticle delivery, the payload is still usually a highly toxic substance derived from fossil fuels. Further, little is known about how the delivery medium, especially plastic, will affect the environment, but there is already evidence that micro- and nanoscale plastics can increase the toxicity of some pesticides. They can also carry other contaminants into the bodies of organisms, a process called the “Trojan horse effect.†Studies of micro- and nanoplastics have shown associations with damage to genes, neurotransmission, development and reproduction, feeding, and predatory competence.
Policymakers have yet to face up to the presence of nanoplastics leaching from packaging into many other products. The process of leaching begins as soon as a plastic is exposed to water—but because the plastic particles are so small, they go undetected by consumers.
In the Columbia/Rutgers study, the researchers checked for seven types of plastic, but they were only able to identify about ten percent of the nanoparticles they found. Polyethylene terephthalate (PET) was a common ingredient, probably because many water bottles are made of it. However, they also found polyamide, polystyrene, polyvinyl chloride, and polymethyl methacrylate. (Tap water also contains microplastics in many places, although in much lower concentrations.) The team found that the number of individual chemical compounds varied wildly among products, ranging from 114 to 2,456, leading them to conclude that “assessing the toxicity of plastic chemicals present in a product based on testing individual target chemicals has limited value.†The Norwegian scientists also exposed cod eggs, embryos and larvae to water containing microplastics. The toxic effects they observed include spinal deformities reminiscent of scoliosis in humans.
Beyond Pesticides covered a 2022 Danish study of reusable plastic sports bottles. The researchers tested two groups of plastic bottles: one set of newly purchased bottles and another of bottles that had been used for about a year, with a control group of glass bottles. They rinsed the new bottles with tap water and discarded it before refilling with tap water and storing for 24 hours. Next they ran all the bottles through a dishwasher for an hour, during which the water temperature reached about 150 degrees Fahrenheit. Finally, they put all the bottles through two more rounds of rinsing, refilling and storing for a day.
The results were dramatic. When they tested the final stored water, they found more than 400 substances associated with the plastic and more than 3,500 dishwashing compounds. Water from the new bottles held 350 unique chemicals, 230 of which were removed by the dishwasher and by rinsing. The used bottles contained 3,436 chemicals, about two-thirds of which were removed by dishwashing. It was clear that the dishwashing produced far more leached chemicals than simply rinsing with tap water and left an enormous residue of its own chemicals. In addition to the expected chemicals from the plastic and the dishwasher soap, the researchers found a number of chemicals they were unable to precisely identify and had never been reported in plastic.
There are many other problems inherent in nanoscale materials that should act as red flags in the development of nanoscale pesticides and their modes of delivery. Nanoscale objects have some qualities owing to their physical characteristics and others stemming from their chemistry. In fact, one group of researchers proposed that nanoscale plastics in the environment must be treated as distinct from both natural and engineered nanomaterials because of their “high particle heterogeneity and their potential for rapid further fragmentation in the environment. These characteristics impact environmental fate, potential effects on biota and human health, sampling and analysis.â€
Nanoscale objects can go anywhere. In the environment, plastic clothing fibers spread even farther and faster than spherical particles. When inhaled, nanoplastics can penetrate lung and intestinal tissue and reach the circulatory system quickly. They can cross the blood-brain barrier, one of the strongest protections the body provides to protect the brain. They can also travel up the olfactory nerve from the nose to the brain.
3-D printing is a prime example of the failure to anticipate and control nanoplastic exposure. In many high-end research and manufacturing contexts, a variety of materials such as metal powders are used to build machines and parts according to specified digital instructions. But down at the low end of the cost spectrum, consumer 3-D printers use primarily ABS plastic: Acrylonitrile-butadiene-styrene filaments. There are even plastic children’s 3-D printers printing ABS plastic objects. Each component of ABS plastic is a either a known or probable carcinogen in its own right. Further, ABS, like most plastics, is a mixture rather than a compound of its ingredients, meaning the components are not chemically bonded and are easily separated. In 3-D printers, ABS heats up enough to separate into its component parts. The 3-D process releases nanoscale particles into the room unless the printer is enclosed, which many are not. In the best-case scenario, the nanoscale plastic particles are vented to the outside air.
Another problem with nanomaterials is their surface area. The smaller something is, the more surface area it has compared to its volume. Thus, a nanoparticle of a pesticide or a nanoparticle of a plastic medium for pesticide delivery will have much greater surface area than a macroscale unit. This makes nanoparticles much more chemically reactive than macroscale materials. The chemical reactivity of nanomaterials may be one reason why the studies discussed above found so many unidentified chemicals in water and water bottles.
The Norwegian researchers tested whether it was the shape and size of the particles or their chemistry that was responsible for the damage to their aquatic test animals. They exposed the cod to particles of the same shape and size but without known toxic effects and found that with plastics, it is definitely the chemistry that does the damage. Flexible plastics and combinations of toxic compounds seemed to have the worst effects.
There are a few lights on the horizon hinting that we may eventually be able to capture and render harmless the trillions of tons of plastic already blanketing the globe. In 2022, for the first time, the United Nations Environment Assembly adopted a resolution entitled “End plastic pollution: Towards an international legally binding instrument.†The Assembly hopes to reach a final agreement by the end of this year. In April 2023 the U.S. EPA produced a similar Draft National Strategy to Prevent Plastic Pollution.
A major step forward both nationally and internationally would be a public policy and legal structure that would prevent the chemical industry from merely making small changes to problematic formulas and declaring the result a new, safe chemical. The Endocrine Society published a statement on the UN resolution noting that once bisphenol A (BPA) was shown to be an endocrine disrupter, the industry switched to bisphenol B and several other closely related compounds, resulting in what became a “regrettable substitution†that was not an improvement on the original problem.
Mother Nature may eventually provide a little help. Knowable Magazine reports that there are numerous efforts around the world to develop enzymes, insects, and bacteria into useful ways to cope with the Sorcerer’s Apprentice plague of plastics threatening human and ecosystem survival.
In the meantime, let your elected officials know that the combined problem of pesticides and plastics stems from the vast use of fossil fuels, that organic agriculture can feed the world without these scourges, and that it is past time to regulate them honestly. See Beyond Pesticides webpage on organic agriculture, as well as our advocacy efforts to continually improve organic standards at our Keeping Organic Strong page.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Sources: Researchers surprised at levels of toxicity in standard plastic products, Christina Benjaminsen, Norwegian University of Science and Technology, https://phys.org/news/2023-12-toxicity-standard-plastic-products.html; MicroLEACH (Microplastics – Long-term Effects of plastics and Additive Chemicals on marine organisms), https://www.niva.no/en/projects/microleach; Bottled water can contain hundreds of thousands of previously uncounted tiny plastic bits, study finds A new microscopic technique zeroes in on the poorly explored world of nanoplastics, which can pass into blood, cells and your brain COLUMBIA CLIMATE SCHOOL, https://www.eurekalert.org/news-releases/1030312; Exposure to petroleum-derived and biopolymer microplastics affect fast start escape performance and aerobic metabolism in a marine fish,  https://www.sciencedirect.com/science/article/pii/S0048969723060503?via%3Dihub; The living things that feast on plastic https://knowablemagazine.org/content/article/food-environment/2023/how-to-recycle-plastic-with-enzymes, The Global Plastics Treaty: An Endocrinologist’s Assessment Marina Olga Fernandez, Leonardo Trasande, https://academic.oup.com/jes/article/8/1/bvad141/7420190.
