Smoke from tobacco products is a known risk factor associated with attention deficit hyperactivity disorder (ADHD) and it is present in the environment in more ways than the obvious. A team of researchers at Duke University says second-hand tobacco smoke is a known environmental risk factor for ADHD so it’s important that expectant mothers not only refrain from smoking, they are advised to stay away from other people smoking, too.

The Duke University study, led by Susan K. Murphy, an Associate Professor of Obstetrics and Gynecology at the University’s School of Medicine and Center for Study of Neurodevelopment and Improving Children’s Health, cites another recent study that indicates as many as half of all the children in the United States are exposed to second-hand smoke. This exposure may affect the way their neurological development advances by affecting gene regulation.

The 2007 study indicates more than 5 million US children have been diagnosed with ADHD and their collective medical care costs as much as $42.5 billion every year. The Duke study is designed to “substantially improve our overall understanding of the environment’s role - including exposure to tobacco smoke - in ADHD,” according to Murphy.

Murphy says the risk of ADHD is about 76 percent genetic but environmental factors determine which risk factors are expressed and which remain dormant. The expression of a gene, any gene, is characterized by whether or not it turns on to produce a genetic trait. This turning on and off of gene expression is known as the science of epigenetics.

The Duke study will focus on the effects of second-hand smoke but third-hand smoke is likely to be just as toxic. Third-hand smoke is the oily residue that clings to surfaces when the air becomes cleared of smoke.

Third-hand smoke collects on toys, floors, upholstered furniture and bedding, tables, chairs, and any other surface in a room that doesn’t get cleaned on a regular basis. Toddlers and young children spend a great deal of time on the floor, putting almost everything they can reach into their mouths, where the smoke residue can enter their bloodstream. Pets are vulnerable to third-hand smoke, too, and kids love to romp and roll with their furry friends, even when the pet’s fur may be glazed with third-hand smoke residue.

It’s very important to be aware of the many ways tobacco smoke can contaminate an environment, especially when a pregnant woman or small children share the environment.

Source: “Smoke exposure during pregnancy and ADHD investigated.” UPI Health News. United Press International, Inc. Dec 26, 2013. Web. Dec 30, 2013.