Environmental dust granulometry and microbial load in the presence of tobacco smoke

Several studies describe damage from passive smoking in humans. However, it is not clearly understood how different chemical and physical components relate to mechanisms of damage. This investigation was focused on the particulate phase of environmental cigarette smoke. The size of particles is very important in the inhalation process and subsequent deposition of particles in the airways.

The granulometry of suspended dust and bacterial particles was studied in a 120-m(3) no-smoking room during and after the smoking of one cigarette in ten separate experiments. Granulometry was assessed by a six-channel particle counter. Suspended microbial load was evaluated by a surface air system. The sedimented bacterial load was evaluated by the air microbial index technique, which expresses the total number of microorganisms settling on a Petri plate under gravity.

The number of large particles increased during the first minute of smoking, and then decreased to basal levels. The number of medium-sized particles increased during the first 10 min of cigarette smoking, and then decreased to basal levels. The number of small particles increased over the whole experimental period. Bacterial and mycotic load decreased during and up to 60 min after cigarette smoking. Gram-positive cocci did not decrease, while chromogenous bacteria and mycetes decreased at 30 min. There was an increase in the numbers of sedimented bacteria and mycetes at 60 min, a decrease at 120 min and stabilization at 180 min.

Smoking of tobacco accelerates the sedimentation of larger agglomerates of mean-sized smoke particles and bacteria, which may be re-suspended by the movement of people in the room and consequently inhaled.