SCIENCE

Link From Weather to Pollution

When and where power plants emit nitrogen oxide can make a huge difference in the health effects of air pollution, a new study finds.

Measuring emissions from a power plant in eastern Pennsylvania in July 1995, Princeton University scientists found that a given amount of nitrogen oxide produced much more ground-level ozone on warmer days than on cooler ones. On hot days, they calculated, emissions from a plant upwind of a densely populated area could lead to more than three times as many deaths as in cool weather.

Denise L. Mauzerall, lead author of the study published in the May issue of the journal Atmospheric Environment, said the findings were significant in light of the Bush administration's plans for a "cap and trade" program for power plant emissions in the eastern United States. The Clean Air Interstate Rule finalized in March aims to cut overall nitrogen oxide emissions from utilities by 61 percent in the next decade, but missions from individual plants may vary widely.

"When and where [emissions take place] makes a big difference in how much damage is done," Mauzerall said in an interview.

Utilities lobbyist Scott Segal said an approach that sought to minimize emissions at particular times would penalize plants that "have to operate 24 hours a day, seven days a week, 365 days a year."

"A rule like that would hit ratepayers really, really hard," he said, adding that utilities have to produce more electricity in summer to meet air conditioning needs.

-- Juliet Eilperin

Kids Poor Judges of Slow Speed

Ever wonder why children can't hit the softball or tennis ball even when you throw it oh so slowly?

It is easy to understand, vision scientist Terri Lewis said. "Kids can't judge slow speeds. They can't tell that the ball's moving at all." The solution: "Give it a little more oomph. They'll do better."

Lewis, of Canada's McMaster University, in Hamilton, Ontario, studied the reactions of adults and 5-year-olds as they watched sets of lines moving laterally across a computer screen and tried to guess which set was moving faster.

"Adults aren't particularly good with slow speeds," Lewis said in a telephone interview. "But kids are three times worse." The research is to be published in the July issue of the journal Vision Research.

Lewis said the human brain, at any age, does not have very many neurons to deal with anything in slow motion, and the shortcoming is dramatically worse in the brain of a child. It works with lateral movement and movement toward and away from the viewer.

This, Lewis said, is why kids swing erratically when Dad throws the tennis ball and might not swing at all when he throws it more slowly. It is why the baseball bounces off the kid's catcher's mitt, why the kid looks at you for instructions instead of at the ball, and why it doesn't help if you yell "Now!"

-- Guy Gugliotta