Comparison of Fresh and Room-Aged Cigarette Sidestream Smoke in a Subchronic Inhalation Study on Rats

Abstract

Two experimental types of cigarette sidestream smoke (SS) were compared in a subchronic inhalation study on rats. Fresh SS (FSS) was generated continuously from the reference cigarette 2R1. Room-aged SS (RASS) was generated by aging FSS for 1.5 h in a room with noninert surfaces with materials typically found in residences or offices. Male Sprague-Dawley rats were head-only exposed to three dose levels of each SS type and to filtered, conditioned fresh air (sham-exposure) for 6 h/day, 7 days/week, for 90 days. Room-aging resulted in decreased concentrations of various SS components, e.g., total particulate matter (TPM) and nicotine, while other components, such as carbon monoxide (CO), were not affected. The CO concentrations were 6, 13, and 28 ppm for both SS types. TPM concentrations were between 0.6 and 8.7 micrograms/liter and thus up to 100-fold above the maximum of average concentrations of respiratory suspended particles reported for environmental tobacco smoke. Slight reserve cell hyperplasia in the anterior part of the nose as well as hyperplastic and metaplastic epithelial changes in the larynx were the only observed dose-dependent findings. The metabolism of benzo(a)-pyrene--as a proxy for polycyclic aromatic hydrocarbon metabolism--was induced in the nasal respiratory epithelium and in the lungs while no effect was seen in the nasal olfactory epithelium. The lowest-observed effect level was 6 ppm CO or 0.6 microgram TPM/liter. Most of the effects seen were less expressed in RASS-than in FSS-exposed rats when compared on the basis of the CO concentrations. When compared on the basis of TPM, these effects were equally pronounced for both SS types, suggesting a major role of particulate matter-associated compounds. All findings reverted to sham control levels following a 42-day postinhalation period.

Lung Inflammation in Rats Following Subchronic Exposure to Cigarette Mainstream Smoke

“…There was a postexposure period of 28 days to check for the potential reversal of smoke-induced effects (all groups except the cellulose group). Type IC88 exposure chambers equipped with glass tubes were used with tube sizes according to the individual body weight of the rats [14]. The flow of the test atmospheres through the exposure chambers was between 34 and 60 L=min except for the 2R1, which was conveyed with a flow rate of 180 L=min.…”

“…The analytical methods used to determine TPM, carbon monoxide (CO), aldehydes (formaldehyde, acetaldehyde, acrolein), and nicotine in the test atmospheres were performed as described previously [14].…”

“…The larynges were fixed in EAFS (ethanol-acetic acid-formaldehydesaline) for 2 days and then stored in 70% ethanol; noses were fixed in 10% neutral-buffered formaldehyde solution for 2 days and then stored in 4% buffered formaldehyde solution until embedding in paraffin [14]. Because of the extensive lavage procedure, lungs were not processed for histopathology.…”

Mechanisms Involved in A/J Mouse Lung Tumorigenesis Induced by Inhalation of an Environmental Tobacco Smoke Surrogate

“…Both MS and SS were generated on an automatic 30-port smoking machine (Haussmann et al, 1998a(Haussmann et al, , 1998b. The cigarettes were conditioned and smoked in basic accordance with the International Organization for Standardization (ISO) standards 3402 (ISO, 1991) and 3308 (ISO, 2000).…”

“…Particle size distribution was determined 4 times within the 5-mo treatment period. The analytical methods used to determine temperature, relative humidity, TPM, CO, nicotine, 3-ethenyl pyridine, solanesol, carbon dioxide, nitrogen oxides, aldehydes, ammonia, and particle size distribution were as previously described (Haussmann et al, 1998a(Haussmann et al, , 1998b.…”