We will monitor pollution by (checks notes) dispersing a huge swarm of tiny robots, themselves made of heavy metals, that are infeasibly difficult to recover or recycle.
There is a video that demonstrates and explains the nano bots in the article and near the end of the video they stated that the bots are made out of biodegradable materials that will degrade with time/rain
Everything degrades over a long enough timescale, even plastics and metals. The question is what damage they do to ecosystems on their long cycle to be atomized and recycled.
Pretty sure any magnet strong enough to attract one of these from the distances required would also induce a voltage on any sufficiently long wire that’s moving through the flux lines. i.e. might cause problems for your car, for airplanes, etc.
> It's neither a bird nor a plane, but a winged microchip as small as a grain of sand that can be carried by the wind as it monitors such things as pollution levels or the spread of airborne diseases.