A study from the University of Minnesota suggests that secondhand cigarette smoke may be more hazardous to children than to adults.

Looking at children living in a household where at least one parent smoked, the study found the level of a specific tobacco carcinogen in the children's urine was about 8% of that normally found in a smoker. This is considerably higher than the level previous studies have found in adults exposed to secondhand smoke.

This suggests that as bad as secondhand smoke is for adults, it's that much worse for children.

About one-third of children in the U.S. live in a home with at least one smoker. The researchers hope that the study results will cause more parents to keep their home smoke-free for the sake of their children.

The study measured the amount of a compound called NNAL in the children's urine. NNAL is produced by the body as a metabolite (end product) of the tobacco compound NNK (nicotine-derived nitrosamine ketone). NNK is a known human carcinogen. For details, see the American Cancer Society website's Known and Probable Carcinogens.

The researchers took urine samples from 79 children, aged one month to 10 years, who lived in homes where at least one parent smoked. In addition to measuring NNAL, the researchers also measured levels of nicotine and cotinine (a metabolite of nicotine) in the children's urine. They found detectable levels of NNAL and nicotine in 90% of the children and detectable levels of cotinine in 95% of them.

Not surprisingly, the more cigarettes that were smoked in the household, the higher the level was of tobacco metabolites found in the children's urine. The researchers also found an association between lower socioeconomic status, employment and parental education to a child's exposure to secondhand smoke.

The study also found that African-American children had the highest amount of tobacco metabolites in the urine, even when the parents smoked comparatively little. This suggests the possibility of racial differences in how tobacco compounds are metabolized, differences that have been previously seen by other researchers.

About one-third of children in the U.S. live in a home with at least one smoker. The researchers hope that the study results will cause more parents to keep their home smoke-free for the sake of their children.

Cigarette smokers may be feeling extremely put out by the number of restrictions society has placed on them over the last decade or so. Yet most would probably agree that they have a responsibility to avoid lighting up in the presence of those most affected by the smoke. That includes children.

The study was presented at the ninth American Association of Cancer Research (AACR) Frontiers in Cancer Prevention Research Conference. The conference was held in Philadelphia from November 7-10, 2010.