One of my favorite contemporary writers is British author Jasper Fforde. In his 2002 comedy novel Lost in a Good Book, the world is nearly destroyed and all humanity eradicated when a nanodevice, programmed to turn organic matter into a type of strawberry pudding called Dream Topping, runs out of control and cannot stop turning everything within reach into Dream Topping.* Yes, the novel is a comedy, but the premise illustrates one of the primary fears that have become associated with the field of nanotechnology, that tiny “nanobots” will run amok and set off chain reactions that can’t be stopped. In fact, that original apocalyptic scenario was proposed by no less than nanotechnology pioneer Eric Drexler in his seminal book Engines of Creation. Drexler’s “gray goo” (as he called it) was the result of nanomachines replicating themselves exponentially:

Imagine such a replicator floating in a bottle of chemicals, making copies of itself…the first replicator assembles a copy in one thousand seconds, the two replicators then build two more in the next thousand seconds, the four build another four, and the eight build another eight. At the end of ten hours, there are not thirty-six new replicators, but over 68 billion. In less than a day, they would weigh a ton; in less than two days, they would outweigh the Earth; in another four hours, they would exceed the mass of the Sun and all the planets combined—if the bottle of chemicals hadn’t run dry long before.

Drexler’s “gray goo” scenario has been seized upon by science-fiction authors and documentarians alike (The History Channel, notably, has featured it) to illustrate the dangers of the new and emerging field of nanotechnology. Most of the supposed dangers of nanotech are the stuff of science-fiction, but a recent study has found that there is a more prosaic danger: nanoparticle pollution. Many products on the market today already contain nanoparticles. Sunscreens, for example, use tiny (1 to 100 nanometers in size; one nanometer [nm] is one billionth of a meter) nano-zinc and oxide particles to absorb UV radiation while preventing that telltale geeky white residue. Nanoparticles are also used in odor-resistant socks, diesel fuels, and cosmetics. Various environmental and watchdog groups have questioned the safety of these nanoparticles when they interact with the human body, but the new study, published in the Proceedings of the National Academy of Sciences, raises another issue. Says SciTechDaily, metallic nanoparticles used in these consumer products can “end up in the soil, with somewhat troubling consequences.” To wit:

The study examines soybeans growing in soil mixed with two common nanoparticles, nano-zinc oxide and nano-cerium oxide. It suggests that they can accumulate in crops and stunt bacteria that naturally fertilize soil. Other studies have shown that plants can absorb nanoparticles in hydroponic greenhouses, but real soil is quite different. Environmental microbiologist Patricia Holden of the University of California in Santa Barbara states that most nanoparticles would get stuck in clays in soil, so it came as a surprise that they were biologically available to bacteria and plants. This could in turn affect the food supply. Zinc oxide (ZnO) and cerium oxide (CeO₂) are two materials used to fabricate nanoparticles. Nano-zinc uses oxide particles, as small as an HIV virus, to absorb ultraviolet light without leaving a white residue. The particles end up in drains and then transferred into sewage sludge, which is sold to farmers to use as fertilizer. ... Nano-cerium accumulated around the soybeans roots and stunted plant growth while nano-zinc allowed crops to absorb much more zinc than plants grown in regular soil.

Whilst nanotechnology is not the scary doomsday nightmare some have made it out to be, and pollution is hardly limited to nanotechnology, it’s obvious we need to carefully look at the environmental consequences of some of its applications.   * Michael Crichton’s 2003 novel Prey also featured malevolent nanobots. The Fforde novel is a lot more fun.