In fresh evidence about the dangers of coal pollution, a scientist on Monday said a switch to coal-fired power in a southern US state after a nuclear accident in 1979 led to a sharp fall in birthweight, a benchmark of health.

The study looked at the aftermath of the Three Mile Island accident in Pennsylvania, which caused two nuclear plants in Tennessee to be shuttered and their power to be replaced locally by coal generation.

After the energy switch, the weight of newborns fell by 5.4 percent in Tennessee Valley counties that had the highest levels of air pollution from coal particles emitted by the replacement plants, the investigation found.

Birthweight reductions of just over five percent can result in illness, stunted growth and neurodevelopment problems later in life, earlier research has shown. They are also strongly linked to lower IQ and income.

"Average birth weight declined approximately 134 grams (4.7 ounces) after the nuclear shutdown," said Edson Severnini, a researcher at Carnegie Mellon University in Pittsburgh, Pennsylvania. In the most affected places, "infant health may have deteriorated," he added.

The research, published in the peer-reviewed journal Nature Energy, touches on a debate about the risks of coal versus nuclear energy, triggered most recently by the 2011 Fukushima nuclear disaster In Japan.

The accident prompted a slew of countries to curb nuclear plans, resulting in greater use of fossil fuels -- especially coal -- to meet their energy needs.

- Fear of nuclear -

Supporters of nuclear, while acknowledging concerns about accidents, say that the technology has a far better record for safety and public health than coal, which generates particles that are a respiratory hazard as well as climate-altering greenhouse gases.

Scientists estimate that in China and India alone, more than 200,000 people die prematurely each year due to coal pollution.

In contrast, supporters of coal say that pollution technology today is far better than four decades ago, and promote a vision of a "clean coal" with a far lower risk to the environment and health.

US President Donald Trump's administration is currently setting down plans to revive the American coal industry, including in the region examined in this study.

Severnini said the findings of his research call for reflection on the perceived benefits of shuttering nuclear plants.

"The shutdown of nuclear power plants in the United States and abroad might not generate as much net benefit as the public perceives," he suggested.

In a commentary also published in Nature Energy, Michael Shellenberger of US research and policy group Environmental Progress agreed.

"Public fears of nuclear power are widespread, especially in the aftermath of accidents, yet their benefits are rarely considered," he wrote.

"Where the normal operation of coal plants results in significant, measurable health impacts, the Fukushima accident -- the second worse nuclear accident in history -- will have no quantifiable impact on public health outside Japan."

The percentage of global electricity generated by nuclear power has dropped from nearly 18 percent in 1996 to about 11 percent today.