Lightning-produced radiation a potential health concern for air travelers

Published: December 7 2009

Category:Engineering, Research, Sciences

Scientists say incidents are likely rare and more research is needed


Scientists at the , and the have estimated that airplane passengers could be exposed to a radiation dose equal to that from 400 chest X-rays if their airplane happens to be near the start of a lightning discharge or related phenomena known as a terrestrial gamma ray flash.


“We know that commercial airplanes are typically struck by lightning once or twice a year,” said Joe Dwyer, professor of physics and space sciences at Florida Tech. “What we don’t know is how often planes happen to be in just the right place or right time to receive a high radiation dose. We believe it is very rare, but more research is needed to answer the question definitively.”

Dwyer is the lead author of a paper about the research set to appear in the Journal for Geophysical Research — Atmospheres. Seven researchers from Florida Tech, UC Santa Cruz and UF contributed to the paper. “Estimation of the fluence of high-energy electron bursts produced by thunderclouds and the resulting radiation doses received in aircraft.” It is free and downloadable online from the journal’s “papers in press” page. The link is


The authors “combined observations of lightning-produced X-rays and gamma rays with computer models of the movement of high-energy particles to estimate the amount of radiation that could be produced within, or very near, thunderclouds during lightning storms,” said Hamid Rassoul, a co-author and senior researcher from Florida Tech.

The observations included those made from orbiting satellites of “terrestrial gamma-ray flashes,” or TGFs, mysterious phenomena that appear to originate within thunderstorms at the same altitudes used by jet airliners. They also included measurements of X-rays and gamma rays from natural lightning on the ground, as well as artificial lightning triggered with wire-trailing rockets fired into storm clouds. Researchers believe the phenomena are linked, because both produce high levels of gamma rays and X-rays and occur along with the actual lightning flash.

The scientists concluded the radiation in a football field-sized space around these lightning events could reach “biologically significant levels,” up to 10 rem, according to their paper.


Ten rem is considered the maximum safe radiation exposure over a person’s lifetime. It is equal to 400 chest X-rays, three CAT scans or 7,500 hours of flight time in normal conditions. All airplane passengers are exposed to slightly elevated radiation levels due to cosmic rays.

While the research raises obvious concerns, the scientists stressed that they don’t know how often the high-radiation events occur — or how often planes are nearby enough to expose passengers and flight crews to potential danger.


“These observations show that although thunderstorms do occasionally create intense gamma-ray flashes, the chance of accidently being directly hit by one is small,” Smith said.



“What we need to do is supply the right kind of detectors to a lot of planes, and see if this ever happens,” he said. “We also need to spend more time looking at gamma and x-ray radiation from lightning and thunderstorms and trying to understand how it works.”

The paper drew on data from numerous observations and experiments, including experiments involving artificial “triggered” lightning at UF/Florida Tech International Center for Lightning Research and Testing at the Camp Blanding Army National Guard Base near Starke, Florida. UF and Florida Tech researchers at the center were the first to identify X-ray emissions from triggered lightning.


Aaron Hoover,, 352-392-0186
Martin Uman,, 352-392-4038
Joe Dwyer,, 321-674-7208

Category:Engineering, Research, Sciences