New York, April 9 (Inditop) Blood tests show that more than half of non-smokers here have elevated levels of cotinine, a consequence of recent exposure to toxic second-hand smoke.

Cotinine, a by-product of nicotine breakdown, signals exposure to tobacco smoke. A US survey shows that 57 percent of adult New Yorkers (2.5 million) have elevated cotinine levels, compared to 45 percent of adults nationwide.

Among non-smoking New Yorkers, Asian adults were the most likely to have elevated cotinine levels (69 percent). Studies from other parts of the country show that Asian Americans, particularly Chinese Americans, are more likely to smoke at home.

Second-hand smoke contains many harmful chemicals. It is known to cause cancer and heart disease in adults. Women who live with second-hand smoke are more likely to have low-birth-weight babies, pre-term delivery and miscarriage.

It is also especially bad for children. When parents smoke, babies are more likely to die from Sudden Infant Death Syndrome (SIDS). Children have more illnesses, including ear infections and asthma. Teens are more likely to become smokers themselves.

The data comes from the New York City Health and Nutrition Examination Survey, which was conducted in 2004, one year after New York City’s smoke-free air law took effect.

Although the law protects non-smokers from the dangers of second-hand smoke at work and in some public places, this study shows that many non-smokers are not fully protected. Creating a smoke-free home is the most important step that New Yorkers can take to protect their families.

“Tobacco smoke is a toxic pollutant,” said Thomas R. Frieden, New York City Health Commissioner. “Most New York City non-smokers are breathing in dangerous chemicals in second-hand smoke, potentially increasing the risk of cancer and heart disease.”

“The study provides more evidence of the pervasiveness of second-hand smoke,” said Jennifer Ellis, a former health department epidemiologist and the study’s lead author, according to a New York City Health release.

This is the first time researchers have used blood tests to gauge second-hand smoke exposure in New York City.

These findings have been published online this week in Nicotine and Tobacco Research.