Toxicological assessment of a prototype e-cigaret device and three flavor formulations: a 90-day inhalation study in rats.

A prototype electronic cigaret device and three formulations were evaluated in a 90-day rat inhalation study followed by a 42-day recovery period. Animals were randomly assigned to groups for exposure to low-, mid- and high-dose levels of aerosols composed of vehicle (glycerin and propylene glycol mixture); vehicle and 2.0% nicotine; or vehicle, 2.0% nicotine and flavor mixture. Daily targeted aerosol total particulate matter (TPM) doses of 3.2, 9.6 and 32.0 mg/kg/day were achieved by exposure to 1 mg/L aerosol for 16, 48 and 160 min, respectively. Pre-study evaluations included indirect ophthalmoscopy, virology and bacteriological screening. Body weights, clinical observations and food consumption were monitored weekly. Plasma nicotine and cotinine and carboxyhemoglobin levels were measured at days 28 and 90. After days 28, 56 and 90, lung function measurements were obtained. Biological endpoints after 90-day exposure and 42-day recovery period included clinical pathology, urinalysis, bronchoalveolar fluid (BALF) analysis, necropsy and histopathology. Treatment-related effects following 90 days of exposure included changes in body weight, food consumption and respiratory rate. Dose-related decreases in thymus and spleen weights, and increased BALF lactate dehydrogenase, total protein, alveolar macrophages, neutrophils and lung weights were observed. Histopathology evaluations revealed sporadic increases in nasal section 1-4 epithelial hyperplasia and vacuolization. Following the recovery period, effects in the nose and BALF were persistent while other effects were resolved. The no observed effect level based upon body weight decreases is considered to be the mid-dose level for each formulation, equivalent to a daily TPM exposure dose of approximately 9.6 mg/kg/day.

Insights from two industrial hygiene pilot e-cigarette passive vaping studies.

While several reports have been published using research methods of estimating exposure risk to e-cigarette vapors in nonusers, only two have directly measured indoor air concentrations from vaping using validated industrial hygiene sampling methodology. Our first study was designed to measure indoor air concentrations of nicotine, menthol, propylene glycol, glycerol, and total particulates during the use of multiple e-cigarettes in a well-characterized room over a period of time. Our second study was a repeat of the first study, and it also evaluated levels of formaldehyde. Measurements were collected using active sampling, near real-time and direct measurement techniques. Air sampling incorporated industrial hygiene sampling methodology using analytical methods established by the National Institute of Occupational Safety and Health and the Occupational Safety and Health Administration. Active samples were collected over a 12-hr period, for 4 days. Background measurements were taken in the same room the day before and the day after vaping. Panelists (n = 185 Study 1; n = 145 Study 2) used menthol and non-menthol MarkTen prototype e-cigarettes. Vaping sessions (six, 1-hr) included 3 prototypes, with total number of puffs ranging from 36-216 per session. Results of the active samples were below the limit of quantitation of the analytical methods. Near real-time data were below the lowest concentration on the established calibration curves. Data from this study indicate that the majority of chemical constituents sampled were below quantifiable levels. Formaldehyde was detected at consistent levels during all sampling periods. These two studies found that indoor vaping of MarkTen prototype e-cigarette does not produce chemical constituents at quantifiable levels or background levels using standard industrial hygiene collection techniques and analytical methods.

A comprehensive toxicological evaluation of three adhesives using experimental cigarettes.

CONTEXT: Adhesives are used in several different manufacturing operations in the production of cigarettes. The use of new, "high-speed-manufacture" adhesives (e.g. vinyl acetate based) could affect the smoke chemistry and toxicology of cigarettes, compared with older "low-speed-manufacture" adhesives (e.g. starch based). OBJECTIVE: This study was conducted to determine whether the inclusion of different levels of three adhesives (ethylene vinyl acetate, polyvinyl acetate and starch) in experimental cigarettes results in different smoke chemistry and toxicological responses in in vitro and in vivo assays. MATERIALS AND METHODS: A battery of tests (analytical chemistry, in vitro and in vivo assays) was used to compare the chemistry and toxicology of smoke from experimental cigarettes made with different combinations of the three adhesives. Varying levels of the different side-seam adhesives, as well as the transfer of adhesives from packaging materials, were tested. RESULTS: There were differences in some mainstream cigarette smoke constituents as a function of the level of adhesive added to experimental cigarettes and between the tested adhesives. None of these differences translated into statistically significant differences in the in vitro or in vivo assays. CONCLUSION: The use of newer "high-speed-manufacture" vinyl acetate-based adhesives in cigarettes does not produce toxicological profiles that prevent the adhesives from replacing the older "low-speed-manufacture" adhesives (such as starch).

Benchmark dose risk assessment for formaldehyde using airflow modeling and a single-compartment, DNA-protein cross-link dosimetry model to estimate human equivalent doses.

Formaldehyde induced squamous-cell carcinomas in the nasal passages of F344 rats in two inhalation bioassays at exposure levels of 6 ppm and above. Increases in rates of cell proliferation were measured by T. M. Monticello and colleagues at exposure levels of 0.7 ppm and above in the same tissues from which tumors arose. A risk assessment for formaldehyde was conducted at the CIIT Centers for Health Research, in collaboration with investigators from Toxicological Excellence in Risk Assessment (TERA) and the U.S. Environmental Protection Agency (U.S. EPA) in 1999. Two methods for dose-response assessment were used: a full biologically based modeling approach and a statistically oriented analysis by benchmark dose (BMD) method. This article presents the later approach, the purpose of which is to combine BMD and pharmacokinetic modeling to estimate human cancer risks from formaldehyde exposure. BMD analysis was used to identify points of departure (exposure levels) for low-dose extrapolation in rats for both tumor and the cell proliferation endpoints. The benchmark concentrations for induced cell proliferation were lower than for tumors. These concentrations were extrapolated to humans using two mechanistic models. One model used computational fluid dynamics (CFD) alone to determine rates of delivery of inhaled formaldehyde to the nasal lining. The second model combined the CFD method with a pharmacokinetic model to predict tissue dose with formaldehyde-induced DNA-protein cross-links (DPX) as a dose metric. Both extrapolation methods gave similar results, and the predicted cancer risk in humans at low exposure levels was found to be similar to that from a risk assessment conducted by the U.S. EPA in 1991. Use of the mechanistically based extrapolation models lends greater certainty to these risk estimates than previous approaches and also identifies the uncertainty in the measured dose-response relationship for cell proliferation at low exposure levels, the dose-response relationship for DPX in monkeys, and the choice between linear and nonlinear methods of extrapolation as key remaining sources of uncertainty.