Thirdhand Exposures to Tobacco-Specific Nitrosamines through Inhalation, Dust Ingestion, Dermal Uptake, and Epidermal Chemistry

Tobacco-specific nitrosamines (TSNAs) are emitted during smoking and form indoors by nitrosation of nicotine. Two of them, N'-nitrosonornicotine (NNN) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), are human carcinogens with No Significant Risk Levels (NSRLs) of 500 and 14 ng day^-1, respectively. Another TSNA, 4-(methylnitrosamino)-4-(3-pyridyl) butanal (NNA), shows genotoxic and mutagenic activity in vitro. Here, we present additional evidence of genotoxicity of NNA, an assessment of TSNA dermal uptake, and predicted exposure risks through different pathways. Dermal uptake was investigated by evaluating the penetration of NNK and nicotine through mice skin. Comparable mouse urine metabolite profiles suggested that both compounds were absorbed and metabolized via similar mechanisms. We then investigated the effects of skin constituents on the reaction of adsorbed nicotine with nitrous acid (epidermal chemistry). Higher TSNA concentrations were formed on cellulose and cotton substrates that were precoated with human skin oils and sweat compared to clean substrates. These results were combined with reported air, dust, and surface concentrations to assess NNK intake. Five different exposure pathways exceeded the NSRL under realistic scenarios, including inhalation, dust ingestion, direct dermal contact, gas-to-skin deposition, and epidermal nitrosation of nicotine. These results illustrate potential long-term health risks for nonsmokers in homes contaminated with thirdhand tobacco smoke.

Determination of 4-(Methylnitrosamino)-1-(3-Pyridyl)-1-Butanone (NNK) arising from tobacco smoke in airborne particulate matter

The most important tobacco-specific nitrosamine found in cigarette smoke and formed in ageing smoke after cigarettes are extinguished is 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). It is formed from nitrosation of nicotine, under particular conditions both in indoor and outdoor environments. NNK has been classified as a potent lung carcinogen which is expected to be found primarily in the particle-phase and to be stable in particulate matter. In this study tests have been carried out to show that a bisulfate-treated filter is more efficient than an untreated filter to collect both nicotine and NNK, and that the latter is stable in outdoor particulate matter. To characterize NNK in the outdoor environment, airborne samples were collected from 11 cities in USA, UK, Hong Kong and Malta with characteristics varying from low to high population densities and from urban to suburban to rural, and with desert characteristics and distinct climates. It has been shown that airborne particle + gas phase nicotine and particle-phase NNK behave in a linearly correlated manner. A seasonal analysis was carried out on a subset of data available from five sites in California, where the load of NNK in PM10 is driven by long range transport of the air masses passing over densely populated cities. In the winter season, the load of NNK in PM is higher than in summer in a statistically significant manner. The contamination of PM with NNK shows variability, but is observed at all sites. This paper highlights the potential risk of chronic exposure to NNK in particulate matter by the inhalation pathway.

Ubiquitous atmospheric contamination by tobacco smoke: Nicotine and a new marker for tobacco smoke-derived particulate matter, nicotelline

Second Hand Smoke (SHS) has always been primarily linked with indoor pollution. To date nicotine was the favoured marker for SHS alongside measurements of particulate matter (PM) levels. As nicotine is mainly found in the gas-phase and reactive in the outdoor environment it is not ideal as a marker for the SHS-driven particulate component in PM. Nicotelline, a minor tobacco alkaloid that is stable, found almost exclusively in the particle phase and easy to quantify even at low concentrations, is being proposed as a better marker. It is the first study using bisulfate-treated quartz fiber filters to show that airborne nicotine (gas+particle phase) is directly proportional to airborne nicotelline in countries that have different climates. The analytical method developed has been validated to show that the use of untreated filters is suitable for the quantification of nicotelline even at low concentrations. Although nicotelline exhibits a seasonal and geographical variation, this is the first comprehensive study which demonstrates the ubiquitous presence of nicotelline in PM from outdoor air samples collected in the USA (0.1-285.6 pgm^-3), UK (2.3-9.1 pgm^-3), Hong Kong (3.8-109.3 pgm^-3) and Malta (4.2-280.8 pgm^-3). From the nicotelline apportionment factor of 1589 ng/mg of tobacco smoke PM we estimate the fraction of outdoor airborne PM derived from SHS to be in the range of 0.03-0.08%. While it is unlikely for tobacco smoke-related toxics in outdoor PM to be considered a major health hazard, in heavily polluted microenvironments this marker would be useful in tracing the presence of SHS and emerging Third Hand Smoke components that form or are found in airborne and settled PM that could induce serious health effects.

Vascular endothelial function is impaired by aerosol from a single IQOS HeatStick to the same extent as by cigarette smoke

BACKGROUND

Heated tobacco products (also called 'heat-not-burn' products) heat tobacco at temperatures below that of combustion, causing nicotine and other compounds to aerosolise. One such product, IQOS from Philip Morris International, is being marketed internationally with claims of harm reduction. We sought to determine whether exposure to IQOS aerosol impairs arterial flow-mediated dilation (FMD), a measure of vascular endothelial function that is impaired by tobacco smoke.

METHODS

We exposed anaesthetised rats (n=8/group) via nose cone to IQOS aerosol from single HeatSticks, mainstream smoke from single Marlboro Red cigarettes or clean air for a series of consecutive 30 s cycles over 1.5-5 min. Each cycle consisted of 15 or 5 s of exposure followed by removal from the nose cone. We measured pre-exposure and postexposure FMD, and postexposure serum nicotine and cotinine.

RESULTS

FMD was impaired comparably by ten 15 s exposures and ten 5 s exposures to IQOS aerosol and to cigarette smoke, but not by clean air. Serum nicotine levels were similar to plasma levels after humans have smoked one cigarette, confirming that exposure conditions had real-world relevance. Postexposure nicotine levels were ~4.5-fold higher in rats exposed to IQOS than to cigarettes, despite nicotine being measured in the IQOS aerosol at ~63% the amount measured in smoke. When IQOS exposure was briefer, leading to comparable serum nicotine levels to the cigarette group, FMD was still comparably impaired.

CONCLUSIONS

Acute exposures to IQOS aerosol impairs FMD in rats. IQOS use does not necessarily avoid the adverse cardiovascular effects of smoking cigarettes.

Electronic cigarette chemicals transfer from a vape shop to a nearby business in a multiple-tenant retail building

BACKGROUND

Electronic cigarettes (ECs) are nicotine delivery devices that produce aerosol without combustion of tobacco; therefore, they do not produce sidestream smoke. Nevertheless, many users exhale large clouds of aerosol that can result in passive exposure of non-users. Analogous to thirdhand cigarette smoke, the exhaled aerosol also settles on indoor surfaces where it can produce a residue. We refer to this residue as EC exhaled aerosol residue (ECEAR). Our objective was to determine if exhaled EC aerosol transferred from a vape shop in a multiple-tenant retail building, where it was produced, to a nearby business (field site) where it could deposit as ECEAR.

METHODS

We examined the build-up of ECEAR in commonly used materials (cotton towel and paper towels) placed inside the field site across from the vape shop. Materials were subjected to short-term (days) and long-term (months) exposures. Nicotine, other alkaloids and tobacco-specific nitrosamines (TSNAs) were identified and quantified in controls and field site samples using analytical chemical techniques.

RESULTS

Nicotine and other alkaloids were detected after 1 day of exposure in the field site, and these chemicals generally increased as exposure times increased. TSNAs, which have been linked to carcinogenesis, were also detected in short-term and long-term exposed samples from the field site.

CONCLUSIONS

In a multiple-tenant retail building, chemicals in EC aerosol travelled from a vape shop into an adjacent business where they deposited forming ECEAR. Regulatory agencies and tenants occupying such buildings should be aware of this potential environmental hazard.

IQOS: examination of Philip Morris International's claim of reduced exposure

BACKGROUND

New electronic heated tobacco products are being introduced in the global market and are gaining popularity. In 2016, Philip Morris International, Inc. (PMI) submitted a modified risk tobacco product (MRTP) application to the Food and Drug Administration (FDA) to market IQOS in the USA with claims of reduced exposure and reduced risk.

METHODS

We examined PMI's MRTP application, specifically sections on aerosol chemistry and human exposure assessment, to assess the validity of PMI's claims of reduced exposure and risk.

FINDINGS

PMI reported levels for only 40 of 93 harmful and potentially harmful constituents (HPHCs) on FDA's HPHC list in IQOS mainstream aerosol. All substances in PMI's list of 58 constituents (PMI-58) were lower in IQOS emissions compared with mainstream smoke of 3R4F reference cigarettes. However, levels of 56 other constituents, which are not included in the PMI-58 list or FDA's list of HPHCs, were higher in IQOS emissions; 22 were >200% higher and seven were >1000% higher than in 3R4F reference cigarette smoke. PMI's studies also show significantly lower systemic exposure to some HPHCs from use of IQOS compared with smoking combustible cigarettes.

CONCLUSION

PMI's data appear to support PMI's claim that IQOS reduces exposure to HPHCs. However, PMI's data also show significantly higher levels of several substances that are not recognised as HPHCs by the FDA in IQOS emissions compared with combustible cigarette smoke. The impact of these substances on the overall toxicity or harm of IQOS is not known.

Stereoselectivity in the human metabolism of methamphetamine

AIM

To characterize the formation and urinary elimination of metabolites of S-(+) and R-(-) methamphetamine (MA) in humans.

METHODS

In this 12-subject, six-session, double-blind, placebo-controlled, balanced, crossover design study, the formation of the MA metabolites para hydroxymethamphetamine (pOH-MA) and amphetamine (AMP) were determined in urine after intravenous doses of S-(+)-MA 0.25 and 0.5 mg kg(-1), R-(-)-MA 0.25 and 0.5 mg kg(-1), racemic MA 0.5 mg kg(-1), or placebo. Parent drug and metabolite levels in urine and plasma were measured by gas chromatography-mass spectrometry. Pharmacokinetic parameters were calculated by noncompartmental models using WinNonlin.

RESULTS

An approximately threefold enantioselectivity difference in elimination was observed for AMP, with 7% of the dose converted to S-(+)-AMP vs. 2% to R-(-)-AMP (P < 0.001). Furthermore, less R-(-)-pOH-MA was excreted in the urine compared with S-(+)-pOH-MA (8% vs. 11%, P= 0.02). Correspondingly, S-(+)-MA excretion was less than R-(-)-MA (42% vs. 52%; P= 0.005).

CONCLUSIONS

The metabolism of MA is enantioselective, with formation of AMP having the highest isomer selectivity. A greater percentage of MA is converted to pOH-MA (8-11%) than AMP (2-7%). The formation of pOH-MA was less affected by the MA enantiomer administered, suggesting that urine pOH-MA may be a more stable biomarker of MA metabolism.

Effects of nicotine on cytochrome P450 2A6 and 2E1 activities

AIMS

Smoking slows the metabolism of nicotine and accelerates the metabolism of chlorzoxazone, which are probe reactions for cytochrome P450 2A6 (CYP2A6) and CYP2E1 activities, respectively. We aimed to determine the role of nicotine in these metabolic effects of cigarette smoking.

METHODS

The study had a single-blind, randomized, crossover two-arm design. Twelve healthy smokers were given two transdermal patches with 42-mg nicotine a day or placebo patches, each for 10 days. The subjects abstained from smoking during the study arms. Oral chlorzoxazone was given on day 7 and deuterium-labelled nicotine-d(2) and cotinine-d(4) infusion on day 8.

RESULTS

There was no significant influence of transdermal nicotine administration on pharmacokinetic parameters of nicotine-d(2) or on the formation of cotinine-d(2). Nicotine decreased the volume of distribution (62.6 vs. 67.7 l, 95% confidence interval of the difference -9.7, -0.6, P= 0.047) of infused cotinine-d(4). There were no significant differences in disposition kinetics of chlorzoxazone between the treatments.

CONCLUSIONS

CYP2A6 and CYP2E1 activities are not affected by nicotine. The tobacco smoke constituents responsible for the reduced CYP2A6 and increased CYP2E1 activities remain unknown.