It is already widely known that exposure to tobacco smoke during development harms children, with non-coding ‘epigenetic’ changes to DNA reported repeatedly as a result. Moreover, the knowledge that smoking during pregnancy will have a negative impact on the unborn fetus, making him or her at risk of suffering from conditions such as asthma, is nowadays widely accepted.
“..the smoke-induced defect in these enzymes was transmitted to second-generation [grandchildren] animals.”
A recent study has indicated that this risk from second hand smoke is likely to extend further, affecting even the offspring of any fetus that has been exposed. “Second-hand cigarette smoke exposure during pregnancy has damaging effects that could last for generations,” said Hitendra Chand, a biomedical researcher at the Herbert Wertheim College of Medicine.
Researchers from the Chand lab and the Lovelace Respiratory Research Institute, conducted the study on animal models, and were surprised to find adverse effects in second-generation animals that had never been exposed to the smoke. “We observed a smoke-related defect in the enzymes that produce hydrogen sulfide, a vital signal transmitter [messenger] that helps regulate organ development,” said Chand. “And the smoke-induced defect in these enzymes was transmitted to second-generation [grandchildren] animals.”
The researchers added that these enzymes could potentially serve as a biomarker for determining the future susceptibility of asthma in children. Additionally, these findings have significant implications in raising further awareness against the risks of smoking.
The risk of asthma for children with smoking fathers
Similarly, a 2019 study of Taiwanese families looked at paternal smoking during the mother’s pregnancy and its effects on immune system genes, found that babies have a greater risk of developing asthma if their father smoked before their birth.
Published in Frontiers in Genetics, the paper revealed how immune genes can predict the level of risk, and found that just like maternal smoking or air pollution, paternal smoking during pregnancy can also program epigenetic modifications, which in turn increase the associated risk of childhood asthma.
The researchers had looked for signs of asthma in over 1,600 babies, 756 of which were followed for six years. “We found that prenatal exposure to paternal tobacco smoking is associated with increased methylation of certain immune genes, which alters how the genetic code is read,” says lead author Dr Wu Chih-Chiang of Po-Jen Hospital in Kaohsiung, Taiwan. “This smoking associated DNA methylation is significantly retained from birth to six years of age, and correlates with development of childhood asthma.”