New findings by a group of Colorado researchers indicates lightning could be the culprit in a number of unexplained fatal heart malfunctions in the outdoors in recent years, including some in the state's high mountains.
In an article published in the June 13 issue of Lancet, a highly regarded medical journal published weekly in London, the Colorado team proposed that lightning can kill without a visible sign of electrical current entering or leaving a person's body.
In most lightning fatalities, victims exhibit external damage such as skin burns where electrical currents have entered or exited the body, the scientists said. Some victims, however, show no sign of external burns, indicating they were not touched by the lightning itself. Biophysical calculations by the research team indicate that in such cases, intense magnetic fields resulting from the lightning may induce fatal electrical currents entirely within the body.
The researchers authoring the Lancet letter include Dr. Michael Cherington, a neurologist at St. Anthony Hospital in Denver, Professor Howard Wachtel of the University of Colorado at Boulder's electrical and computer engineering department and Dr. Phillip Yarnell, also a neurologist at St. Anthony Hospital. All are members of the Lightning Data Center research group that meets monthly in Denver to discuss the medical aspects of lightning and other electrical injuries and deaths.
Wachtel, who has spent much of his career researching the impact of electromagnetic fields on human health, said the results of the research are still speculative. "But our calculations indicate the magnetically induced currents within the body during a vulnerable cardiac period could be strong enough to disrupt and fibrillate the heart, possibly causing death."
The researchers also have speculated that in some fatal cases of "hiker heart attacks" in Colorado's high country, lightning strikes near the victims could have provided enough of a magnetic field to induce a brief, severe current causing death. Since most of the cases involved solitary hikers, witnesses were generally lacking, said Wachtel.
"It is known that perfectly healthy people go off hiking in the mountains and suddenly succumb to heart attacks," said Wachtel. "We think this hypothesis may help explain some of these occurrences."
Lightning can kill at any altitude, the researchers stressed. In one case cited by the authors in Lancet, a foursome of golfers standing under a tree that was struck by lightning. One golfer sustained burns, two were knocked unconscious and a fourth who suffered cardiac arrest died about three weeks later, although he exhibited no evidence of external burns or other physical damage from lightning.
Although varying studies estimate from 100 to 400 people are killed annually in the nation by lightning, the death toll probably is underestimated, said Wachtel. New Mexico ranks first in lightning fatalities with 1.88 deaths per million people annually, while Colorado ranks sixth with 1.04, according to a 1987 report by the National Oceanic and Atmospheric Administration.
Lightning had been thought to affect victims in one of three ways: a lightning bolt hitting them directly; indirect hits by a "side flash" of lightning that causes electrical current to enter their bodies; or injuries or electrocution by lightning hitting and traveling through the ground. Lightning currents have been known to travel long distances underground, Wachtel said.
"The new magnetic induction hypothesis now presents a fourth route for lightning injury or death," Wachtel said.
Wachtel advises that people caught outdoors in lightning storms run to their vehicles and jump in if time permits. If not, he advises they assume a "baseball-catcher position" with their feet close together and hold their hands over their ears to minimize the impact of the electrical field of lightning and the accompanying noise.
Contact:
Howard Wachtel, (303) 492-7713
Dr. Michael Cherington, 629-3652
Jim Scott, 492-3114
Journal
The Lancet