Carbon nanotubes could behave like asbestos
The glacial pace with which governments started to regulate asbestos use has put thousands of lives in jeopardy and it’s a disaster that we could do with not repeating. But while asbestos is yesterday’s construction material, a new substance being heralded as the building material of tomorrow has the potential to cause similar health risks – carbon nanotubes.
A new study suggests that carbon nanotubes can cause asbestos-like damage if they are injected into the bodies of mice. The results are cause for concern but not panic. The study didn’t show that the nanotubes can build up in body cavities of their own accord, nor if this damage would eventually result in the mesotheliomas that asbestos can cause. It does however show that we are running before we can walk if the widespread commercial use of carbon nanotubes goes unregulated without rigorous research on their safety.
Wonder-material
Carbon nanotubes are the poster child of the nanotechnology revolution. They are long cylinders made up of carbon atoms. Each tube is a single molecule and they can also be stacked one inside the other to form multi-walled cylinders with many layers. They can be several millimetres in length, but are usually only a few nanometres in diameter; tens of thousands could fit in the width of a single human hair
The nanotubes are among the strongest and stiffest materials on earth, and excel at conducting both heat and electricity. Their earliest use was probably to create really sharp swords. But in the 21st century, their unique combination of desirable properties that has put them at the head of a billion-dollar manufacturing industry that is expected to grow substantially over the next few years. The hype around nanotechnology is growing just as quickly if not more so, but it has also been tempered by concerns over their safety.
There is an assumption by some that since carbon nanotubes are simply rolled sheets of carbon atoms, they would pose no greater a threat to health than simple graphite does. But it is their structure, not their chemical composition, that is most concerning. Their small scale and needle-like shape is superficially similar to that of asbestos fibres.
It is these fibres that do the damage. If inhaled they can cause chronic inflammation in the lungs – asbestosis – as well as lung cancer. If the fibres travel out of the lung, they can accumulate in the surrounding cavity, the pleura, and trigger the development of tumours in the membrane that surrounds it, the mesothelium. The resulting cancer, mesothelioma, is almost entirely caused by asbestos fibres. The worry then, is that the consequences of taking an inadvertent whiff of carbon nanotubes would parallel those of inhaling asbestos.
Long and short of it
It’s long asbestos fibres that cause the problems, by disproportionately inflaming the sensitive mesothelium. Short fibres have little effect. To see if carbon nanotubes behaved similarly, Craig Poland at the University of Edinburgh injected mice with four samples of carbon nanotubes, two short and two long, as well as both short and long asbestos fibres. The fibres were injected at low doses straight into their abdominal cavity.
After the injections, Poland washed out the cavity with a saline solution to study the molecules and cells within it. In mice injected with long fibres, be they asbestos or nanotubes, this washed-up liquid contained immune cells and proteins that indicated strong inflammation.
In these groups, Poland also found signs of granulomas, scar-like structures on the surface of the mesothelium made up of clumped immune cells. They form when white blood cells come across material they cannot digest like long carbon nanotubes that are wider than the cell’s own diameter (see right). The frustrated cells then continuously release chemicals that trigger inflammation.
Poland describes his results as predictable but “unwelcome”. They show that there is potential for long carbon nanotubes to cause asbestos-like damage in a living animal. But they are a long way from demonstrating an actual danger. Without the easy entry afforded by an injecting needle, carbon nanotubes could only pose similar risks to asbestos if they could become airborne, be easily inhaled and migrate from the lungs to the mesothelium in sufficient numbers. For the moment, we don’t know if they can. Nor do we know if the damage observed in the mice would eventually lead to full-blown mesothelioma.
Poland believes that both questions need to be answered “with some urgency” if we are to avoid another disaster on the scale of asbestos. The answers may strongly could influence both the regulation and the manufacture of nanotechnology, especially since Poland also found that short carbon nanotubes don’t mimic the effect of asbestos.
Reference: doi:10.1038/nnano.2008.111
Images: nanotubes by Michael Strock, cell image from Nature, asbestos by Aram Dulyan
Related Topics
Go Further
Animals
- Octopuses have a lot of secrets. Can you guess 8 of them?
- Animals
- Feature
Octopuses have a lot of secrets. Can you guess 8 of them? - This biologist and her rescue dog help protect bears in the AndesThis biologist and her rescue dog help protect bears in the Andes
- An octopus invited this writer into her tank—and her secret worldAn octopus invited this writer into her tank—and her secret world
- Peace-loving bonobos are more aggressive than we thoughtPeace-loving bonobos are more aggressive than we thought
Environment
- Listen to 30 years of climate change transformed into haunting musicListen to 30 years of climate change transformed into haunting music
- This ancient society tried to stop El Niño—with child sacrificeThis ancient society tried to stop El Niño—with child sacrifice
- U.S. plans to clean its drinking water. What does that mean?U.S. plans to clean its drinking water. What does that mean?
- Food systems: supporting the triangle of food security, Video Story
- Paid Content
Food systems: supporting the triangle of food security - Will we ever solve the mystery of the Mima mounds?Will we ever solve the mystery of the Mima mounds?
History & Culture
- Strange clues in a Maya temple reveal a fiery political dramaStrange clues in a Maya temple reveal a fiery political drama
- How technology is revealing secrets in these ancient scrollsHow technology is revealing secrets in these ancient scrolls
- Pilgrimages aren’t just spiritual anymore. They’re a workout.Pilgrimages aren’t just spiritual anymore. They’re a workout.
- This ancient society tried to stop El Niño—with child sacrificeThis ancient society tried to stop El Niño—with child sacrifice
- This ancient cure was just revived in a lab. Does it work?This ancient cure was just revived in a lab. Does it work?
Science
- The unexpected health benefits of Ozempic and MounjaroThe unexpected health benefits of Ozempic and Mounjaro
- Do you have an inner monologue? Here’s what it reveals about you.Do you have an inner monologue? Here’s what it reveals about you.
- Jupiter’s volcanic moon Io has been erupting for billions of yearsJupiter’s volcanic moon Io has been erupting for billions of years
- This 80-foot-long sea monster was the killer whale of its timeThis 80-foot-long sea monster was the killer whale of its time
Travel
- How nanobreweries are shaking up Portland's beer sceneHow nanobreweries are shaking up Portland's beer scene
- How to plan an epic summer trip to a national parkHow to plan an epic summer trip to a national park
- This town is the Alps' first European Capital of CultureThis town is the Alps' first European Capital of Culture
- This royal city lies in the shadow of Kuala LumpurThis royal city lies in the shadow of Kuala Lumpur