Are Nanomaterials Really Silent Killers That Harm Health? (Part 2)
Release time:
2023-06-08
In the SIN study on carbon nanotube-induced lung damage, only one type of longer carbon nanotube was examined. However, evidence suggests that shorter carbon nanotubes are significantly less toxic. Therefore, indiscriminately treating all carbon nanotubes as a single material in the SIN is an unjustified practice.
In the study on carbon nanotube-induced lung damage conducted by SIN, only one type of longer carbon nanotube was involved. However, evidence suggests that shorter carbon nanotubes are significantly less toxic. Therefore, indiscriminately incorporating all carbon nanotubes as a single material into SIN is an unreasonable (unjustified) practice.
The article opposing ChemSec, published in Nature Nanotechnology, features an unusually long list of authors. Immediately afterward, 39 scholars jointly published a commentary firmly opposing the inclusion of carbon nanotubes in the SIN.
This article, which features a long list of authors, further demonstrates the unreasonableness of ChemSec’s move. They point out that numerous studies have shown “ There is insufficient evidence or limited impact regarding the carcinogenicity of CNTs. ”。
More importantly, they pointed out that including carbon nanotubes in the SIN list would severely hinder technological innovation. While human health and environmental protection are indeed top priorities, new technologies must continue to be explored and refined. “Only when we gain a sufficiently deep understanding of a material will we be more likely to discover effective ways to harness its potential.” Today, carbon nanotubes are widely used in the medical field—for instance, to enhance cell differentiation, deliver drugs precisely, or enable molecular imaging. If all carbon nanotubes were indiscriminately placed on the SIN list, research in these fields would inevitably suffer a serious blow.
Carbon nanotubes hold tremendous potential for a wide range of applications, including batteries, integrated circuits, novel coatings and adhesives, pharmaceuticals, and more. | www.mdpi.com
Carbon nanotubes are just the first shot in the “battle over nanomaterial toxicity”; soon after, one nanomaterial after another will enter the discussion. Graphene, quantum dots, nano-gold, nano-silver, silicon nanowires—this list could go on and on. Evaluations of these materials have been ongoing, yet currently, much of the available data remains insufficient. As you can imagine, the controversy surrounding nanomaterials and the SIN list is bound to persist.
Why should we be concerned about nanomaterials?
When we talk about nanomaterials, what exactly are we afraid of?
Afraid of their smallness.
Nanomaterials refer broadly to materials in which at least one dimension—out of the three spatial dimensions—is on the nanoscale (1 to 100 nanometers). The diameter of a single human hair is roughly 60,000 to 80,000 nanometers. This significant reduction in scale endows nanomaterials with many extraordinary properties. As a result, many people believe that these new materials will trigger the next technological revolution.
With the advancement of technology, an increasing number of nanomaterials are entering human society. According to a 2015 report, the number of commercially available nanomaterials had already exceeded 1,800; today, that figure has undoubtedly grown significantly. In 2019, the global market value of nanomaterials was US$8.5 billion, and according to analyses by relevant institutions, this figure is expected to rise to US$22 billion by 2027.
From mobile phones to cosmetics, from furniture to dyes—nanoparticles in these products can easily detach and enter the atmosphere, rivers, and soil. Moreover, many pollutants generated in human production and daily life are also at the nanoscale. Among the indicators used to assess air pollution, there’s one called PM0.1, which refers to particulate matter in the ambient air with a diameter of less than 100 nanometers.
Particulate matter with diameters ranging from 5 to 10 micrometers can enter the nasal cavity and pharynx; for these particles, humans can typically cough them out. However, when particles become smaller—such as PM2.5 particles (with diameters less than 2.5 micrometers)—they can penetrate deeper into the trachea and bronchi, directly damaging the alveoli and posing a greater threat to human health. As for even smaller nanoparticles, their harmful effects may be even more severe, since they are small enough to bypass the body’s natural “physiological barriers.”
The so-called “physiological barriers” come in many forms, such as the blood-brain barrier, the blood-placenta barrier, and the blood-testis barrier, among others. These barriers act like protective membranes, separating vital organs from the bloodstream while allowing nutrients to pass through and keeping harmful substances isolated from the organs themselves. However, studies have shown that nanosilver can penetrate the blood-brain barrier in rats, and nanogold particles can cross the placental barrier in pregnant mice, entering the fetal body.
Compared to larger particles, nanoparticles can travel deeper and farther within the human body.
On the other hand, monitoring nanoparticles poses a significant challenge.
We can pick up plastic bottles and recycle used batteries, ensuring that factories don’t discharge wastewater and purifying exhaust gases. These are all things we can see and touch, making them easier to manage. But when we move down to the nanoscale, many of the detection and control methods we’ve relied on for conventional pollutants become ineffective.
In 2015, researchers detected carbon nanotubes in the lungs of dozens of asthmatic children in the Paris region. In the paper reporting this study, the researchers explicitly stated that they had located the carbon nanotubes using a transmission electron microscope—technique that would have been impossible to achieve with conventional optical microscopy. Therefore, they strongly recommend “a reassessment of previous related studies.”
They have a stronger ability to invade the human body and are so tiny that they’re virtually impossible to guard against—this is the hidden danger posed by nanomaterials and nano-scale pollutants.
What should we do?
As a professional in the nanotechnology industry, my personal advice is: “Don’t be afraid—just wait and see.”
First, don't be afraid.
We keep seeing one after another report demonstrating the toxicity of certain nanomaterials. Yet it’s important to point out that researchers and the media naturally tend to overlook data showing a material is non-toxic—such findings are seldom published or widely publicized. After all, the result “This stuff isn’t toxic” doesn’t seem particularly “eye-catching.” As a consequence, what we’re often presented with are precisely those “shocking” reports.
Although nanomaterials have many applications, the types that ordinary people can actually come into contact with are still quite limited, and the quantities they can encounter are extremely small. Some toxicity studies on nanomaterials involve directly injecting high-dose samples into animals. Fortunately, we’re not laboratory mice—we won’t encounter such greater risks.
In fact, our human bodies have many ways to deal with nanoparticles. For example, phagocytic cells can engulf and degrade nanoparticles; many nanomaterials can also be metabolized via the digestive tract or kidneys and subsequently excreted from the body.
As for “just wait and see,” let’s not jump to conclusions too quickly.
After all, nanomaterials are an emerging technology, and toxicological studies on nanomaterials have only just begun. Currently, most of the data available are still one-sided, and in many cases, research reports even contradict each other.
Carbon nanotubes have been around for 30 years, making them one of the “older generation” of nanomaterials. Despite their wide range of applications, research on carbon nanotubes still sparks considerable controversy. It’s worth noting that Chinese scholars have made significant contributions to the study of the biological toxicity of carbon nanotubes. For instance, Chen Chunying and her colleagues at the National Center for Nanoscience and Technology have systematically investigated how factors such as the shape, structure, and length of carbon nanotubes influence their biological properties. They were also among the first to establish a set of standardized criteria for evaluating the biological toxicity of carbon nanotubes.
Of course, when it comes to a popular science article on toxicity, what readers undoubtedly want to see are definitive statements like, “This stuff is toxic—let’s stay away,” or “That one isn’t toxic—you can use it with confidence.” But when it comes to the toxicity of nanomaterials, we’re still mired in thick fog and far from reaching any conclusive conclusions.
What we should fear more than nanomaterials themselves are blind decision-making or the clamor of following the crowd.
Please give the scientists some time.
Keywords:
Are nanomaterials really silent killers that pose a threat to health?
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