It has long been the view of experts that second hand smoke (SHS) can be harmful to both smokers and non smokers alike. It is now recognised that exposure to SHS, especially among young people, can influence their risk of taking up smoking as biologically, inhaled smoke increases the urge to smoke.

A recent study, Effect of Second hand Smoke on Occupancy of Nicotinic Acetylcholine Receptors in Brain, took 11 moderately dependent cigarette smokers and 13 non smokers and exposed them to second hand smoke (SHS). This was achieved by exposing them to 1 hour of SHS in a controlled environment (the inside of a closed car).

Pre and post exposure, participants underwent positron emission tomography and provided plasma for testing of nicotine levels. Participants also rated their SHS-related symptoms (e.g., running nose) and tobacco urges on analogue scales.

Symptoms after SHS exposure did not differ between groups; in smokers, however, cravings increased, and lower thalamic occupancy correlated with greater relief after smoking, which was permitted after scanning.

According to the findings in this report, SMS can also add to the maintenance of cigarette smoking in smokers who are exposed to smoke even when they themselves are not smoking the cigarette. So by just being around a smoker, they are more likely to remain addicted to smoking.

The report said that “Despite progress in tobacco control, second hand smoke (SHS) exposure remains prevalent worldwide and is implicated in the initiation and maintenance of cigarette smoking.”

Conclusions
Nicotine from SHS exposure resulted in substantial brain α4β2* nAChR (nicotinic acetylcholine receptor) occupancy in smokers and non-smokers alike. Findings from the study suggested that such exposure delivered a priming dose of nicotine to the brain that contributed to continued cigarette use in smokers.

The report recognised the need for intensified public health campaigns to reduce SHS exposure, especially in venues that families may not recognize (e.g., parks, street fairs).

Writer Helen Splarn. Editor Dr Ramesh Manocha.
Source: Brody AL et al. Effect of secondhand smoke on occupancy of nicotinic acetylcholine receptors in brain. Arch Gen Psychiatry 2011 May 2