Tobacco byproducts found in newborns

By Lori Valigra, UPI Science News Copyright 1998 United Press International August 23, 1998

Mothers who smoke while pregnant may be passing on a tobacco-specific cancer-causing substance to their fetuses and newborn babies. A federally funded study has shown for the first time that the urine of newborn babies of mothers who smoked while they were pregnant contains byproducts of a lung carcinogen only found in tobacco. This is the first direct evidence that smoking mothers transmit the substance to developing fetuses, said Stephen Hecht, the University of Minnesota Cancer Center scientist who conducted the study. He called the finding an ''unacceptable risk,'' although researchers still do not know what actual impact the substances has on the fetus and the child. Hecht presented his research Sunday at the American Chemical Society meeting in Boston. His work was funded by the National Cancer Institute. ''This presents an unacceptable risk to fetuses, and it is another clear reason why women who are pregnant shouldn't smoke,'' Hecht said. He said the study is the first of its kind. Hecht examined samples of the first urine of 48 German babies, 31 with mothers who smoke and 17 with non-smoking mothers. Using a gas chromatography system, he found none of the byproducts in newborns of non-smokers. However, they were present in 22 of the 31 samples from newborns whose mothers smoked during pregnancy. Hecht said there was a correlation between the number of cigarettes smoked per day and the levels of the byproducts. Hecht measured levels of two byproducts of nicotine-derived nitrosamino ketone (NNK). NNK is the only known lung carcinogen that is found solely in tobacco. It is formed during the curing, aging, processing and smoking of tobacco. The byproducts are NNAL and NNAL- Gluc. The levels of NNAL plus NNAL-Gluc found in the newborns were about 10 percent as great as in the urine of adult smokers. ''This is substantial when one considers that exposure of the developing fetus to NNK would have taken place throughout pregnancy, while the fetus was changing in size,'' Hecht said. About 61 percent of smoking women who become pregnant do not quit smoking during pregnancy. Hecht says most of them continue to smoke after the baby is born, exposing their children to the carcinogen for many years. Some 20 percent to 25 percent of pregnant women in America smoke, about the same ratio as that of smokers in the general population. Hecht said that NNAL and NNAL-Gluc form rapidly when NNK enters a person, and it takes longer than nicotine for the two byproducts to disappear from the body once a person stops smoking. Most nicotine disappears within a couple days, while it can take upwards of 20 weeks to virtually eliminate NNAL and NNAL-Gluc from the body. Researchers still do not know whether exposure to NNK means the newborn will develop cancer. Nor do they know what quantity might be dangerous. Steven Milloy, publisher of the Junk Science Internet home page, says Hecht's results are meaningless without a link between a fetus being exposed to a carcinogen and the development of childhood cancer. ''There is no body of evidence showing that exposure of a fetus causes an increase in cancer in children of smokers,'' Milloy said. ''Pregnant women shouldn't smoke. But if a pregnant women hasn't stopped smoking, this study isn't a reason to do so.'' Leslie Robison, an epidemiologist at Children's Cancer Group and associate director for population sciences at the University of Minnesota Medical Center, said that despite inconclusive data on links between maternal smoking and childhood cancer, the study gives epidemiologists greater incentive to study how NNK might cause cancer. ''To identify the carcinogens in the urine of a newborn is a major documentation of the potential role and the transmission of those compounds,'' Robison said. National Cancer Institute section chief and biologist Lucy Anderson agrees. ''This is the first direct chemical proof that these compounds reach the fetus, and that fetuses have considerable capability to metabolize them,'' Anderson said. The study also indicates that some fetuses are better able to detoxify NNK, she said. For example, NNAL is known to be carcinogenic, but NNAL-Gluc is not likely to be. Hecht's measurements found more NNAL- Gluc than NNAL in the positive samples. ''These findings suggest the majority of fetuses may be protected by their ability to detoxify NNK,'' Anderson said. Last year Hecht reported the first evidence that NNK byproducts were found in the urine of non-smoking adults exposed to secondhand smoke in the work place. He said German scientists have since confirmed that finding.

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