Telling people how pollution can harm kids' health inspires them to use less electricity than telling them how much money they could save by cutting back on power use, US researchers said Monday.

The study in the Proceedings of the National Academy of Sciences centered on people living in 118 apartment units in Los Angeles.

Over the course of about four months, residents were given weekly feedback about their energy usage.

Some were told how their electricity use compared to a more energy-efficient apartment nearby, and how much money they could save by turning off the lights and using less power.

Another group was given similar feedback, but were also told about how much their energy use contributed to pollutant emissions, and how air pollution can cause childhood health problems like cancer and asthma.

A control group received no feedback at all.

The apartments that received the health-related warnings began using an average of eight percent less power than the control group.

If there were kids in the household, apartment dwellers reduced their electricity use by 19 percent, said the study.

Apartments that were told about cost savings from using less energy barely changed their habits at all.

Researchers said that touting monetary savings may not have worked, in part because electricity in the United States is already fairly inexpensive.

"For most people at our field site, the savings for cutting back to using the same as their most efficient neighbor would only be $4 to $6 per month. That's a fast-food combo meal or a couple of gallons of milk," said co-author Omar Asensio, a doctoral student studying economics and environmental sciences and engineering at the University of California, Los Angeles.

But changes in daily habits could be significant on a large scale because residential and commercial buildings account for more than two-thirds of US energy usage, according to the study.

"We're finding that you have to bundle the public good with the private good," said lead author Magali Delmas, an environmental economist at the University of California, Los Angeles (UCLA) Anderson School of Management.

"Our message about health and the environment reminds people that environmentalism is also about them and their kids."