It has been well established that exposure to second hand tobacco smoke can significantly increase risk of asthma and heart disease. Some, but not all studies, have also reported that exposure to second hand smoke by non smokers can increase risk of lung cancer. Exposure to second hand smoke may also damage mental function as well.
A recent study published in the February 12, 2009 British Medical Journal examined mental function in 4,809 non smokers aged 50 years or more. Exposure to second hand smoke was measured by the levels of cotinine in the saliva. (Cotinine is a metabolite of nicotine from tobacco smoke.) Non smokers with high levels of second hand smoke exposure were more likely to suffer cognitive deficits such as poorer memory, lower intelligence or slower reaction time as compared to non-smokers with little exposure to second hand tobacco smoke. Results were adjusted for many other factors including alcohol and drug use.
The exact relationship between second hand smoke exposure and lower mental function is not certain, but could be due to the damage that 2nd hand smoke exposure causes to blood vessels.
A number of states and communities are instituting smoking bans to reduce rates of heart disease, asthma, cancer. Smoking bans can also reduce risk of fires. A number of studies have already reported significantly lower rates of asthma attacks following indoor smoking bans. Adults should never smoke when near small children.