Here's another piece of bad news for India's 250 million smokers, especially women.

Children with at least one parent who smokes have been found to have 5.5 times higher levels of cotinine, a byproduct of nicotine, in their urine. A study by researchers from Warwick Medical School and the University of Leicester, published in the Archives of Disease in Childhood on Wednesday, says having a mother who smokes was found to have the biggest independent effect on cotinine in the urine - quadrupling it.

Cotinine was measured in 104 urine samples taken from infants aged 12 weeks, 71 of whom had parents who smoked. Having a smoking father doubled the amount of cotinine. Infants who slept with their parents tended to have higher cotinine levels because they had greater exposure to parents' smoke-contaminated clothing.

The temperature in the child's room also influenced cotinine levels, with lower temperature tied to higher amounts of the nicotine metabolite. Prof Ann Jackson from Warwick Medical School told TOI, "It is now clear that babies are fast becoming heavy passive smokers that will severely damage their physiological development. It's worse when the mother smokes as the baby is usually always in close proximity of the mother."

Dr Mike Wailoo of the University of Leicester added that parental smoking is a leading risk factor for sudden infant death syndrome. "One reason for this could be inhalation of or closeness to clothing or other objects contaminated with smoke particles during sleep. This is the first time we've found the direct effect of cigarette smoke on babies at their home. Cotinine available in such high quantities makes it seem as if the child itself is the smoker."

The study should be an eye-opener for the increasing number of urban women smokers in India. Dr A K Dewan from the Rajiv Gandhi Cancer Institute and Research Centre, said, "In India, about one-third of women use at least one form of tobacco."

Doctors already believe that infants of mothers who smoke are put at almost five times the risk of dying from cot death.