Narrator: This is Science Today. You may want to check the weather report before you decide to do some cleaning around the house. Environmental engineer, William Nazaroff, of the University of California, Berkeley says their research suggests that high outdoor ozone levels could create a harmful combination with chemicals called terpenes, which are found in common household cleaning products and air fresheners.

Nazaroff: If there's some smog advisory that says, “You should be indoors today because the outdoor air pollution's really going to be bad,” then that's not a good day to choose to clean your house.

Narrator: Nazaroff says ozone levels peak during the middle of summer days, and suggests cleaning near the beginning or end of the day.

Nazaroff: Doing your cleaning early in the morning or late in the afternoon or early in the evening, or doing it during a time when the weather happens to be favorable so the ozone levels aren't so high would be a smart move.

Narrator : According to the study, a person who stays in the kitchen using a moderate amount of terpene-containing products on high ozone days, would inhale about one quarter of the total daily guideline value for particulate matter. For Science Today, I'm Larissa Branin.

C. A Study Looks into Stethoscope Accuracy in Cardiac Patients

Narrator: This is Science Today. Over the last two decades, technology – such as echocardiography, a test that uses sound waves to create a moving picture of the heart – has vastly improved the detection of heart disorders. But Dr. Andrew Michaels, an assistant professor of cardiology at the University of California , San Francisco , says at the same time, there's been a decline in the reliability of the physicians' bedside diagnosis.

Michaels: Physicians have tended to spend a little less time at the bedside trying to elicit these physical exam findings. And if they do detect it or don't detect it, they just don't have confidence that they're making an accurate assessment.

Narrator: In a recent study on stethoscope accuracy in cardiac patients, Andrews found that experienced physicians are better able to detect a third heart sound that's an indicator of heart disease.

Michaels: So one thing would be to encourage medical schools and training programs for residents and fellows to spend more time teaching these people how to elicit these physical exam findings.

Narrator: For Science Today, I'm Larissa Branin.

D. How El Niño and La Niña Events Affect Deep Sea Fish Populations

Narrator: This is Science Today. Deep-sea fish populations have tripled in the last fifteen years. Researcher David Bailey of the Scripps Institution of Oceanography at the University of California , San Diego , says the upsurge appears to be driven by an increase in food available to the animals living in the vast, dark plains at the bottom of the ocean.

Bailey: The animals that live on the bottom of the ocean, they get the vast majority of their food from the surface. The vast majority of it falls down as a rain of particles called marine snow, which is basically dead plankton raining down from the surface.

Narrator: Bailey explains that anything that changes the productivity of the surface waters, changes how much food reaches the ocean floor.

Bailey: And El Niño, La Niña and these longer term cycles, they all change how much plankton grows by changing nutrient availability. And what this study shows is that when deep sea fish are left alone, they show large changes in their abundance. These are driven by natural factors, such as oceanographic and climatic changes. And that shows the difference between natural changes and those which are driven by fishing.

Narrator: For Science Today, I'm Larissa Branin.

E. Researchers Get the Green Light to Test Drive a Hydrogen Fuel Cell Vehicle

Narrator: This is Science Today. The Daimler-Chrysler Corporation has handed researchers at the University of California , Berkeley the keys to the F-Cell, their limited production hydrogen fuel cell vehicle. Tim Lipman, a research engineer at UC Berkeley's California Partners for Advanced Transit and Highways, or PATH, is co-manager of the two-year project, which will study the vehicles' use in real-world conditions.

Lipman: I've been studying these fuel cell vehicles for about twelve years now and I really am amazed at technical progress that Diamler-Chrysler and some other companies have made over that period.

Narrator: Hydrogen cars are being explored nationally as an environmentally friendly alternative to gasoline powered vehicles.

Lipman: If you really want to find a fuel that will dramatically cut carbon emissions in the long term and that can also be produced domestically and that also addresses air pollution, I really don't think there's a better option than hydrogen at this point. There are some key technical and economic hurdles, but there's no more promising alternative out there than this hydrogen technology.

Narrator: For Science Today, I'm Larissa Branin.