Nanoparticles Are in Our Food, Clothing and Medicine -- And No One Knows for Sure How Dangerous They Might Be
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They built thirty boxes and a greenhouse to hold them. The large number would make it easier to replicate experiments, and to answer the spectrum of questions being posed by CEINT’s interdisciplinary team. The ecologists were interested in community diversity and how the biomass shifts over time. The biologists wanted to know whether the nanoparticles become concentrated as they move up the food chain. The toxicologists wanted to track where the particles went and how fast they got there. The chemists wanted to know about reactivity.
Whatever the goal of the experiment it houses, each mesocosm features a slanted board upon which a terrestrial ecosystem slowly gives way to an aquatic one. It’s a lot more complicated than a test tube in a lab, but it remains an approximation. The team had hoped to run streams through the mesocosms, but the computing power and monitoring vigilance necessary to track nanoparticles in the streams proved prohibitive.
In 2011, the team dosed the boxes with two kinds of nanosilver made on campus: one coated in PVP, a binder used in many medicines, and the other coated in gum arabic, a binder used in numerous products, including gummi candies and cosmetics. Both coatings help to stabilize the nanosilver. In some boxes, the researchers let the silver leach slowly into the box. In other boxes, they delivered the silver in one big pulse. In some, they introduced the silver into the terrestrial part of the box; in others, they put the silver into the water.
Then the researchers watched and waited.
Reading through descriptions of nanoparticle applications can make a person almost giddy. It all sounds mostly great. And the toxicology maxim “Dose makes the poison” leads many biologists to be skeptical of the dangers nanoparticles might pose. After all, nanoparticles are pretty darn small.
Yet size seems to be a double-edged sword in the nanoverse. Because nanoparticles are so small, they can slip past the body’s various barriers: skin, the blood-brain barrier, the lining of the gut and airways. Once inside, these tiny particles can bind to many things. They seem to build up over time, especially in the brain. Some cause inflammation and cell damage. Preliminary research shows this can harm the organs of lab animals, though the results of some of these studies are a matter of debate.
Some published research has shown that inhaled nanoparticles actually become more toxic as they get smaller. Nano–titanium dioxide, one of the most commonly used nanoparticles (Pop-Tarts, sunblock), has been shown to damage DNA in animals and prematurely corrode metals. Carbon nanotubes seem to penetrate lungs even more deeply than asbestos.
What little we know about the environmental effects of nanoparticles—and it isn’t very much—also raises some red flags. Nanoparticles from consumer products have been found in sewage wastewater, where they can inhibit bacteria that help break down the waste. They’ve been found to accumulate in plants and stunt their growth. Another study has shown that gold nanoparticles become more concentrated as they move up the food chain from plants to herbivores.
“My suspicion, based on the limited amount of work that’s been done, is that nanoparticles are way less toxic than DDT,” says Richard Di Giulio, an environmental toxicologist on the CEINT team. “But what’s scary about nanoparticles is that we’re producing products with new nanomaterials far ahead of our ability to assess them.”
As a society, we’ve been here before—releasing a “miracle technology” before its potential health and environmental ramifications are understood, let alone investigated. Remember how DDT was going to stamp out malaria and typhus and revolutionize agriculture? How asbestos was going to make buildings fireproof? How bisphenol A (BPA) would make plastics clear and nearly shatterproof? How methyl tertiary-butyl ether (MTBE) would make gasoline burn cleanly? How polychlorinated biphenyls (PCBs) were going to make electrical networks safer? How genetically modified organisms (GMOs) were going to end hunger?