Endotoxins in cigarette smoke

A room where people smoke contains dozens or hundreds of times higher air concentrations of endotoxins than smoke-free indoor air. This has been shown by a research team from Lund University. Endotoxin is the name of a group of poisonous substances produced by bacteria and naturally occurring in the air and elsewhere. In normal low concentrations, endotoxins are not dangerous; indeed, they might play a role in protecting us against allergies. But at higher levels of concentration they induce serious inflammatory reactions in the respiratory tract.

Endotoxins have long been known for their powerful capacity to cause inflammations. Dust rich in endotoxins constitutes a health risk in many workplaces and is seen as a key explanation for the high incidence of chronic bronchitis among farmers. Endotoxins from construction materials, dust, plants, etc. in the home can also contribute to asthma. On the other hand, it had not been clearly shown previously that cigarette smoke contains true endotoxins, i.e. bacterial lipopolysaccharides.

In its experiments, the Lund team, headed by Associate Professor Lennart Larsson, has tried to simulate both passive and active smoking. For the latter, they set up equipment that “smoked” a cigarette in 8-10 minutes and captured the contents of the smoke in a filter. For passive smoking, they “smoked” one cigarette every half hour in an unventilated room for seven hours and compared it with a similar room without smoke. The results, presented in the international journal Indoor Air, show that the level of the toxic substances in the air of the smoky room was a full 120 times higher than in a smoke-free room. Moreover, the tobacco endotoxin seemed to be the most aggressive sort among the various forms that exist.

The key to the finding is a unique method of chemical analysis that the Lund scientists have developed over many years to identify endotoxins in clinical trials and environmental tests. Using this method, they have verified the results presented a few years ago by the American scientist Jeffrey Hasday indicating that there may be endotoxins in cigarette smoke.

“This can be one reason why smokers so often suffer from respiratory ailments. The fact that passive smoking entails exposure to extremely high concentrations of endotoxins is an entirely new breakthrough” says Lennart Larsson, who hopes the new knowledge will be of use in anti-smoking campaigns.

The Lund team now wants to move on to see whether endotoxins from tobacco smoke can fasten onto particles of dust, thereby lingering in an environment where someone once smoked. They also aim to study how ventilation influences the levels of endotoxins from cigarette smoke in indoor air.