Measurements on insect wings can tell us how radiation has spread following a leak and the dose they were exposed to.
Bas den Hond

New Scientist
12 May 2016 - 1:02 PM  UPDATED 24 May 2016 - 11:19 AM

Humble insects may be called as witnesses to the next nuclear accident. Shining UV light on their wings reveals how much radiation they have absorbed.

Staff at nuclear plants carry dosimeters, instruments that take real-time measurements of radioactive exposure, usually expressed in grays (Gy). Civilians in the surrounding areas probably won’t have these devices. In the event of an accidental release of radioactive material, this leaves a gap in the data on its dispersal and resulting radioactivity doses, making it hard to estimate health effects by location.

Part of the solution is to investigate how radiation alters materials in the body or in personal property – for example, nails or the glass of a mobile phone. And if no one is present close to a radiation leak, insects may do the job, says Nikolaos Kazakis of the Athena Research Centre in Xanthi, Greece.

“Insects are everywhere,” he says. Their short lives give them an advantage over phones: “They live only a few weeks, so you don’t have to make corrections for natural radiation when you want to measure the accidental dose.”

To prove the concept, he and his colleagues exposed the wings of dragonflies and houseflies to different doses of ionising radiation. The radiation ejects electrons from some atoms in the wings, leaving behind “holes”, the absence of an electron, which behave as particles in their own right.

Flashes of light

As the electrons and holes move around, they may recombine, emitting a flash of light, or may get stuck and stay separated. Shining ultraviolet light on the wings nudges these to recombine. By measuring the resulting flashes, Kazakis and colleagues could detect and measure radiation doses between 10 and 2000 Gy.

Although the approach is very interesting, it may not be sensitive enough to be useful, note Liz Ainsbury and Jonathan Eakins of Public Health England’s Centre for Radiation, Chemical and Environmental Hazards in Chilton.

“Clinically, it is desirable to be able to distinguish between individuals exposed to less than 1 Gy and more than about 2 Gy to support triage in emergency response,” they say. Sunlight could also make the electrons and holes recombine, making many insects that flutter about by day useless for measurement.

Kazakis acknowledges these drawbacks, but says neither is fatal. There is a place for instruments – or critters – that can record doses that will be literally off the scale for more sensitive instruments. As for sunlight being a spoiler, he says it is always possible to make measurements using insects that have stayed in dark places, trapped in an air duct or a basement or even behind furniture. And he has his eye on using a group of insects that keep their hind wings conveniently under cover: cockroaches.

Radiation Measurements, DOI: 10.1016/j.radmeas.2016.03.004

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