U. S. researchers have said that exposure to ground level ozone, a major component of smog, increases the activity of a substance that triggers heart cell death.

It has been reported that Rajat Sethi of Texas A&M Health Science Center Irma Lerma Rangel College of Pharmacy in Kingsville, Texas, and colleagues tested four groups of 10 rats living in clear plastic-glass boxes where they were exposed 8 hours daily for either 28 or 56 consecutive days to either ozone or clean, filtered air.

Sethi said in a statement, "Our study looked for direct evidence of the role of ozone alone in cardiac dysfunction by creating a controlled environment."

The researchers find the hearts of the ozone-exposed rats had increased levels of tumor necrosis factor-alpha, an indication of inflammation linked to a drop in heart protective protein, Caveolin 1, compared with hearts of the control rats.

Sethi explains that this protective protein seems to protect the heart by binding to a chemical that signals cell death.

Researchers have long reported that deaths from lung diseases, heart attacks and strokes are significantly higher on days with high air pollution levels. (With Inputs from Agencies)