Conditions Leading to Ketene Formation in Vaping Devices and Implications for Public Health.

The outbreak of e-cigarette or vaping use-associated lung injury (EVALI) in the United States in 2019 led to a total of 2807 hospitalizations with 68 deaths. While the exact causes of this vaping-related lung illness are still being debated, laboratory analyses of products from victims of EVALI have shown that vitamin E acetate (VEA), an additive in some tetrahydrocannabinol (THC)-containing products, is strongly linked to the EVALI outbreak. Because of its similar appearance and viscosity to pure THC oil, VEA was used as a diluent agent in cannabis oils in illicit markets. A potential mechanism for EVALI may involve VEA's thermal decomposition product, ketene, a highly poisonous gas, being generated under vaping conditions. In this study, a novel approach was developed to evaluate ketene production from VEA vaping under measurable temperature conditions in real-world devices. Ketene in generated aerosols was captured by two different chemical agents and analyzed by gas chromatography-mass spectrometry (GC-MS) and liquid chromatography with tandem mass spectrometry (LC-MS/MS). The LC-MS/MS method takes advantage of the high sensitivity and specificity of tandem mass spectrometry and appears to be more suitable than GC-MS for the analysis of large batches of samples. Our results confirmed the formation of ketene when VEA was vaped. The production of ketene increased with repeat puffs and showed a correlation to temperatures (200 to 500 °C) measured within vaping devices. Device battery power strength, which affects the heating temperature, plays an important role in ketene formation. In addition to ketene, the organic oxidant duroquinone was also obtained as another thermal degradation product of VEA. Ketene was not detected when vitamin E was vaped under the same conditions, confirming the importance of the acetate group for its generation.

Prenatal developmental toxicity studies of allyl alcohol in rats and rabbits.

Allyl alcohol (C3H6O; prop-2-en-1-ol; CAS RN 107-18-6; EINECS 203-470-7) is used as an intermediate/monomer in polymerization reactions producing chemicals/optical resins or as a coupling/cross-linking agent for unsaturated polyester and alkyd resins. Human exposure to allyl alcohol (AA) is restricted to workplace manufacturing facilities where it is used in enclosed systems, which limits release and impact on environmental receptors. To address regulatory questions about possible developmental toxicity, two OECD Guideline studies were conducted. A rat developmental toxicity study found fetal and maternal toxicity, in the form of resorptions and decreased body weight and food consumption, but no teratogenic effects. A rabbit developmental toxicity study was subsequently conducted upon request by the European Chemical Agency in 2011 under the REACH program and likewise reported maternal toxicity in the form of reductions in body weight gain and food consumption, but neither fetal toxicity or teratogenic effects. The results of both studies are presented and compared in this paper. Based on our review of the collective results of these studies, AA is considered non-teratogenic, yet does elicit increased post-implantation loss and reduced fetal body weight, possibly resulting from concomitant maternal toxicity. Based on the results of these studies, a maternal and developmental toxicity No Observed Adverse Effect Level of 10 mg/kg/day was apparent for both species.

A review of the toxicological and environmental hazards and risks of tetrahydrofuran.

We present in this paper a review of the toxicological and environmental hazards, exposures and risks of tetrahydrofuran (THF; CASRN 109-99-9). THF is a polar solvent and monomer that is easily absorbed by all routes of exposure. The acute toxicity of THF is low to moderate by all routes. Irreversible corrosive damage to the eye can result from direct contact. However, THF is neither a skin irritant, nor sensitizer. Studies in vitro and in vivo have shown that THF is not mutagenic. Chronic studies have found benign tumors in the kidneys of male rats and in the livers of female mice. These findings have been examined, and although a mode of action is not known, the weight of evidence suggests that these tumors are likely not relevant to human health, but instead secondary to rodent-specific modes of action. THF produces transient sedative effects in rats at high concentrations but no significant neurobehavioral changes or neuropathology in sub-chronic studies. There were no specific effects reported on reproduction or developmental toxicity in rats or mice, with non-specific developmental toxicity observed only in the presence of significant maternal toxicity. The log K(ow) value for THF is less than 3, indicating a low potential for bioaccumulation. THF is inherently biodegradable, thus is not expected to be environmentally persistent. THF does not present an ecotoxicity hazard based on test results in fish, aquatic invertebrates and plants. Exposures to THF in the workplace, to consumers and via environmental releases were modeled and all found to fall below the derived toxicity thresholds.

Acute inhalation study of allyl alcohol for derivation of acute exposure guideline levels.

An acute, whole-body inhalation study for allyl alcohol in Sprague-Dawley rats was designed to support derivation of AEGL values, with emphasis on establishing NOAELs for irreversible effects of different exposure concentrations and durations. Groups of 10 rats were exposed for 1 hour (0, 50, 200, or 400 ppm), 4 hours (0, 20, 50, or 100 ppm), or 8 hours (0, 10, 20, or 50 ppm). Clinical evaluations were performed during exposure and in an open field within 22-71 minutes after termination of exposure. Clinical pathology, gross necropsy, and histopathology (nasal tissues, larynx, trachea, lungs/bronchi, liver, and kidneys) were evaluated 14 days after exposure. Mortality was limited to 1 male exposed for 8 hours to 50 ppm. Clinical findings of gasping, rales, increased respiration noted at higher exposure levels were rapidly reversed. No treatment-related findings were observed in the liver and kidneys, or in the lungs of surviving animals. Histopathology in the nasal cavity was noted at all exposure levels following 1, 4, or 8 hours of exposure. Mild nasal inflammation was found at the lowest exposure levels (50-ppm/1-hour, 20-ppm/4-hour, and 10-ppm/8-hour). These effects were considered reversible and were not associated with related clinical signs. Severe, irreversible nasal olfactory epithelial lesions were present in 50 ppm/8-hour males. The NOELs for irreversible effects were 400-ppm/1-hour, 100-ppm/4-hour, and 20-ppm/8-hour. The incidence of severe findings was positively dependent on both concentration and the exposure duration. In contrast, the incidence of mild reversible findings did not appear to be dependent on duration.

Fiberglass and Other Flame-Resistant Fibers in Mattress Covers.

Public complaints have raised concerns that some mattresses in the current marketplace may be potential sources of airborne fiberglass. Although mattress foam is often marketed as chemical-free, their cover compositions are not as well understood by the general public. To fill these basic information gaps, the covers of four newly purchased mattresses were sampled and analyzed using polarized light microscopy, SEM-EDS, and FTIR microspectroscopy. Two of the mattress covers contained over 50% fiberglass in their inner sock layers. Up to 1% of the fiberglass had migrated to adjacent fabric layers, representing a potential risk of consumer exposure if the zipper on the outer cover is opened. The observed fiberglass fragments had calculated aerodynamic diameters ranging between 30 and 50 µm, suggesting they are potentially inhalable into the nose, mouth, and throat, but are likely too large to penetrate deeper into the lungs. No fiberglass was observed on the brand new mattresses' outer surfaces. Synthetic fibers also present in the sock layers were consistent with flame resistant modacrylic containing vinyl chloride and antimony. The use of fiberglass and other chemicals in mattress covers poses a potential health risk if these materials are not adequately contained. The apparent non-inclusion of mattress covers in chemical-free certifications suggests that further improvements are needed in mattress labeling and education of consumers.

Effects of E-Cigarette Flavoring Chemicals on Human Macrophages and Bronchial Epithelial Cells.

E-cigarettes utilize a wide range of flavoring chemicals with respiratory health effects that are not well understood. In this study, we used pulmonary-associated cell lines to assess the in vitro cytotoxic effects of 30 flavoring chemicals. Human bronchial epithelial cells (BEAS-2B) and both naïve and activated macrophages (THP-1) were treated with 10, 100, and 1000 µM of flavoring chemicals and analyzed for changes in viability, cell membrane damage, reactive oxygen species (ROS) production, and inflammatory cytokine release. Viability was unaffected for all chemicals at the 10 and 100 µM concentrations. At 1000 µM, the greatest reductions in viability were seen with decanal, hexanal, nonanal, cinnamaldehyde, eugenol, vanillin, alpha-pinene, and limonene. High amounts of ROS were elicited by vanillin, ethyl maltol, and the diketones (2,3-pentanedione, 2,3-heptanedione, and 2,3-hexanedione) from both cell lines. Naïve THP-1 cells produced significantly elevated levels of IL-1ß, IL-8, and TNF-α when exposed to ethyl maltol and hexanal. Activated THP-1 cells released increased IL-1ß and TNF-α when exposed to ethyl maltol, but many flavoring chemicals had an apparent suppressive effect on inflammatory cytokines released by activated macrophages, some with varying degrees of accompanying cytotoxicity. The diketones, L-carvone, and linalool suppressed cytokine release in the absence of cytotoxicity. These findings provide insight into lung cell cytotoxicity and inflammatory cytokine release in response to flavorings commonly used in e-cigarettes.

Cancer and Non-Cancer Risk Concerns from Metals in Electronic Cigarette Liquids and Aerosols.

We evaluated metal concentrations in e-liquids and e-aerosols from eight studies and estimated the range of corresponding cancer and non-cancer risks. Chromium and nickel were the leading contributors to cancer risk, with minor contributions from cadmium, lead, and arsenic. The increased cancer risks, assuming exposure to 2 mL/day, ranged from 5.7 to 30,000 additional cancers in a million e-cigarette users. The average cancer risk was 3 in 1000. Cancer risks in the mid to upper end of these ranges exceed acceptable levels. The hazard quotient (HQ) approach was used to evaluate non-cancer risks. Hazard quotients exceeding 1.0 indicate the possibility for non-cancer adverse health effects. Estimated exposures at the maximum reported concentrations of nickel, chromium, and manganese resulted in HQ values of 161, 1.1, and 1.0, respectively, with additional contributions from lead. The average concentration of nickel resulted in an HQ value of 14. We conclude from these studies that exposure to metals in e-cigarette liquids and aerosols may pose a significant cancer and non-cancer health risk at the mid and upper end of the reported ranges. The device design and heating elements appear to be the main source of metals in e-aerosols. The large range of metals within and across e-cigarette brands indicate the need for improvements in product design, enforced product safety regulations and manufacturing quality control. Implementation of such measures could reduce metal exposure in e-cigarette users.

Severe Lung Injury Associated With Use of e-Cigarette, or Vaping, Products-California, 2019.

Importance: Since August 2019, more than 2700 patients have been hospitalized with e-cigarette, or vaping, product use-associated lung injury (EVALI) across the United States. This report describes the outbreak in California, a state with one of the highest case counts and with a legal adult-use (recreational) cannabis market. Objective: To present clinical characteristics and vaping product exposures of patients with EVALI in California. Design, Setting, and Participants: Case series describing epidemiologic and laboratory data from 160 hospitalized patients with EVALI reported to the California Department of Public Health by local health departments, who received reports from treating clinicians, from August 7 through November 8, 2019. Exposures: Standardized patient interviews were conducted to assess vaping products used, frequency of use, and method of product acquisition. Vaping products provided by a subset of patients were tested for active ingredients and other substances. Main Outcomes and Measures: Demographic and clinical characteristics, level of care, and outcomes of hospitalization were obtained from medical record review. Results: Among 160 patients with EVALI, 99 (62%) were male, and the median age was 27 years (range, 14-70 years). Of 156 patients with data available, 71 (46%) were admitted to an intensive care unit, and 46 (29%) required mechanical ventilation. Four in-hospital deaths occurred. Of 86 patients interviewed, 71 (83%) reported vaping tetrahydrocannabinol (THC)-containing products, 36 (43%) cannabidiol (CBD)-containing products, and 39 (47%) nicotine-containing products. Sixty-five of 87 (75%) THC-containing products were reported as obtained from informal sources, such as friends, acquaintances, or unlicensed retailers. Of 87 vaping products tested from 24 patients, 49 (56%) contained THC. Vitamin E or vitamin E acetate was found in 41 (84%) of the THC-containing products and no nicotine products. Conclusions and Relevance: Patients' clinical outcomes and vaping behaviors, including predominant use of THC-containing products from informal sources, are similar to those reported by other states, despite California's legal recreational cannabis market. While most THC products tested contained vitamin E or vitamin E acetate, other underlying cause(s) of injury remain possible. The California Department of Public Health recommends that individuals refrain from using any vaping or e-cigarette products, particularly THC-containing products from informal sources, while this investigation is ongoing.

Monoamine oxidase inhibitory activity of flavoured e-cigarette liquids.

BACKGROUND AND AIMS: Monoamine oxidase inhibitors have been hypothesised to be important in tobacco dependence, reinforcing the brain's response to nicotine by delaying the degradation of neurotransmitters by monoamine oxidases. The development of electronic cigarettes has provided an alternative nicotine delivery system, which is widely viewed as less toxic than tobacco smoke. However, significant data gaps remain. This paper reports the results of measurements of monoamine oxidase inhibitory activity in a small sample of commercially available, flavoured e-liquids. METHODS: Twelve e-liquids were tested for monoamine oxidase inhibitory activity, using the kynuramine assay and monoamine oxidase enzymes (human, recombinant). Control samples of carrier liquids, propylene glycol and glycerol, and nicotine were also tested. RESULTS: Four e-liquids contained high levels of inhibitory activity, four more were moderately inhibitory. The remaining four e-liquids were mildly inhibitory, while the carrier liquids, and nicotine were inactive at relevant concentrations. The active compounds in the e-liquids were subsequently identified as vanillin and ethyl vanillin. Under some conditions of use, the sampled e-liquids with the highest concentrations of monoamine oxidase inhibitory activity have the potential to expose consumers to physiologically significant levels of MAO inhibitory activity. CONCLUSIONS: While only a small sample of e-liquids was tested, the findings suggest that some flavours have pharmacological actions, with potential to enhance the response to nicotine or to other drugs. The public health implications of these preliminary findings on addiction and smoking cessation warrant exploration and further research.

Analysis and Assessment of Exposure to Selected Phthalates Found in Children's Toys in Christchurch, New Zealand.

Internationally several phthalates are subject to regulatory control regarding maximum allowable concentrations in children's toys. Such regulation is not in place in New Zealand. Phthalates have been associated with developmental toxicity and endocrine disruption. We determined the concentration of seven phthalates in children's toys purchased in Christchurch, New Zealand. These results provided data for an exposure assessment deriving Hazard Indices (HI) for oral and dermal exposure routes in children, based on the concentration of mixtures of phthalates shown by the EU to produce either reproductive/developmental or hepatotoxic effects. Of the 49 toys analyzed, 65% contained at least one phthalate at a concentration of >0.1% by mass; and 35% contained multiple-phthalates at individual concentrations of >0.1%. A HI of 3.4 was derived for the combined exposures to the four phthalates associated with reproductive and developmental effects. A HI of 0.3 was derived for the group of phthalates associated with hepatotoxic effects. Five phthalates were detected at levels exceeding the EU regulatory limit of 0.1% by mass. Risk assessment calculations indicate that, using realistic exposure scenarios, the worst-case combined exposure to phthalates associated with developmental toxicity exceeded a HI of 1 so may cause adverse developmental effects.

Legislation reduces exposure to second-hand tobacco smoke in New Zealand bars by about 90%.

AIM: To measure exposure to second-hand smoke (SHS) in New Zealand bars before and after comprehensive smoke-free legislation enacted on 10 December 2004. METHODS: Cotinine is the main specific metabolite of nicotine and a well-established biomarker for SHS exposure. We measured cotinine levels in saliva of non-smoking volunteers before and after a 3 h visit to 30 randomly selected bars in 3 cities across the country. Two measures of cotinine before the smoke-free law change during winter and spring 2004, and two follow-up measurements in the same volunteers and venues during winter and spring 2005, were included. RESULTS: Before the smoke-free law change, in all bars and in all volunteers, exposure to SHS was evident with an average increase in saliva cotinine of 0.66 ng/ml (SE 0.03 ng/ml). Increases in cotinine correlated strongly with the volunteers' subjective observation of ventilation, air quality and counts of lit cigarettes. However, even venues that were judged to be "seemingly smoke free" with "good ventilation" produced discernable levels of SHS exposure. After the law change, there remained some exposure to SHS, but at much lower levels (mean saliva cotinine increase of 0.08 ng/ml, SE 0.01 ng/ml). Smoking indoors in bars was almost totally eliminated: in 2005 only one lit cigarette was observed in 30 visits. CONCLUSIONS: Comprehensive smoke-free legislation in New Zealand seems to have reduced exposure of bar patrons to SHS by about 90%. Residual exposures to SHS in bars do not result from illicit smoking indoors.

Marlboro UltraSmooth: a potentially reduced exposure cigarette?

AIM: To compare relative toxic emissions scores (RTE) of the carbon filter cigarette Marlboro UltraSmooth (MUS), against regular Marlboro, Holiday, and British Columbian brands. METHOD: MUS cigarettes were purchased in Tampa, Florida; Marlboro regular and Holiday were purchased in Auckland, New Zealand, and all emissions tested by Labstat International Inc, Kitchener, Ontario under Health Canada Intensive (HCI) machine-smoking conditions (55 ml puff per 30 seconds, filter ventilation holes blocked) against: (1) previous same brand emissions tested under ISO (International Organization for Standardization) conditions; (2) ISO and HCI average emissions for 16 regular brands sold in British Columbia (BC), the reference standard. Toxicants, selected by toxicological risk assessment, enabled estimation of an RTE per brand, and RTE per mg of nicotine. RESULTS: The BC standard for RTE in both ISO and HCI test modes, including metals and nitrosamines, was set at 100. Hereafter excluding them, RTE in ISO mode for BC was 97, MUS 4, Marlboro 102, and Holiday regular 99; and in HCI test mode BC was 97, MUS 42, Marlboro regular 107, and Holiday 95. From ISO to HCI, MUS total puff volume increased 50%, from 252 ml to 380 ml; nicotine yield increased 2.6 fold. Normalising for nicotine (RTE per mg nicotine), in ISO test mode, the BC standard was 97, MUS 10, Marlboro regular 124, and Holiday regular 107. In HCI mode, however, MUS/nicotine at 104 exceeded the average BC standard of 97; Marlboro regular was 137, and Holiday regular 97; MUS ranked sixth highest among 18 regular brands. MUS contained 103 mg of carbon in its 304 mg filter, which was 55% ventilated. CONCLUSION: The combined acetate-carbon filter of MUS performed best at low smoke volumes on ISO testing. Under more smoker-realistic intensive machine testing, and correcting for relative nicotine concentration and compensatory smoking, MUS increased the RTE, for all toxicants combined, for carcinogens, and for cardiovascular toxicants, compared with most regular brands. MUS was not a potentially reduced-exposure product (PREP) under smoker-realistic test conditions, and thus would not be expected to reduce overall harm. It is unrealistic to expect that even major design changes, as seen in MUS, or a regulatory framework to enforce such changes, could reduce cigarette smoking mortality risks to acceptable levels.

Demographic and clinical factors as determinants of serum levels of prostate specific antigen and its derivatives.

BACKGROUND: To characterise the association between demographic and clinical factors and levels of total prostate specific antigen (tPSA) and its molecular derivatives complexed PSA (cPSA), free PSA (fPSA) and the ratio of free to total PSA (%fPSA)] in New Zealand Maori, Pacific Islanders and Europeans, in order to determine whether reported ethnic differences in PSA can be explained by lifestyle and social factors. MATERIALS AND METHODS: Demographic and clinical factors were examined in relation to tPSA, fPSA and cPSA levels, in 1405 Maori, Pacific Island and New Zealand European men with no clinical evidence of prostate cancer, in the Wellington region of New Zealand. Any associations between levels of PSA and PSA derivatives and body mass index, smoking status, family cancer history, non-steroidal anti-inflammatory/vitamin supplement usage, number of sexual partners, age at first intercourse, previous vasectomy, marital/partnership status, educational level and socioeconomic status were investigated by backwards stepwise regression analysis, correcting for age, ethnicity and urinary symptoms. RESULTS: Not being married/partnered was associated with increased tPSA, fPSA and cPSA. tPSA and cPSA decreased with regular non-steroidal anti-inflammatory use. cPSA was decreased in subjects with a first degree relative with any form of cancer. tPSA and fPSA were decreased if the body mass index was > 34. fPSA and %fPSA were decreased in current and former smokers. CONCLUSION: Demographic and clinical factors appear to have a significant effect on levels of PSA and its various derivatives and may account for previously observed ethnic differences. It is important that these associations are taken into account when comparing individual PSA results with standard reference ranges.

Ethnic differences in diet and associations with clinical markers of prostate disease in New Zealand men.

OBJECTIVE: To examine ethnic differences in diet and dietary associations with clinical markers of prostate disease in New Zealand men. MATERIALS AND METHODS: A total of 1031 males (616 New Zealand European, 230 Maori and 185 Pacific Islands) aged 40-69 years, with no history of prostate cancer, completed a questionnaire covering diet. A serum prostate specific antigen (PSA) blood analysis was also undertaken. Regression models were developed to examine the ethnic-specific levels of selected dietary components, and their relationship with PSA and urinary symptom scores. RESULTS: The results confirmed previously found ethnic differences in the New Zealand diet. Combined tomato intake was positively-correlated with free PSA and % free PSA (p=0.021, r=0.197 and p=0.011, r=0.096 respectively). Beer intake was negatively-correlated with total PSA (p=0.028, r=-0.071) and free PSA (p=0.004, r=-0.094). CONCLUSION: Ethnic differences found in the consumption of foods (associated with prostate cancer) highlight the possible importance of dietary interactions for ethnic prostate cancer risk. Associations between specific foods and PSA warrant further investigation.

Assessment of ethnic variation in serum levels of total, complexed and free prostate specific antigen. Comparison of Maori, Pacific Island and New Zealand European populations.

AIMS: To determine whether age-adjusted levels of serum total (tPSA) and complexed (cPSA) prostate specific antigen and the ratio of free to tPSA (%fPSA) differ by ethnic group independent of symptomatic disease. METHODS: The serum levels of tPSA, cPSA, and %fPSA in relation to age, ethnicity and obstructive urinary symptoms were examined in 1405 Maori, Pacific Island and New Zealand European men in the Wellington region of New Zealand, and indicative reference range estimates produced. Participants were non-randomly selected from two study populations. RESULTS: tPSA and cPSA increased with age while %fPSA decreased with age in all ethnic groups. Maori showed higher tPSA values in the 60-69 age group than other ethnic groups. cPSA increased more rapidly with age in Maori than in New Zealand Europeans or Pacific Islanders. %fPSA differed according to age across all three ethnic groups. The median and 5th percentile Pacific Island %fPSA values were higher in comparison to the %fPSA reference ranges of all other ethnic groups and were also higher than those reported in other studies. Once adjusted for urinary symptom score, only %fPSA in Pacific Island subjects remained significantly higher than that in New Zealand Europeans (P<0.001). CONCLUSIONS: Our study indicates that %fPSA differs by ethnicity independent of symptomatic prostate disease.

Consideration of rat chronic progressive nephropathy in regulatory evaluations for carcinogenicity.

Chronic progressive nephropathy (CPN) is a spontaneous renal disease of rats which can be a serious confounder in toxicology studies. It is a progressive disease with known physiological factors that modify disease progression, such as high dietary protein. The weight of evidence supports an absence of a renal counterpart in humans. There is extensive evidence that advanced CPN, particularly end-stage kidney, is a risk factor for development of a background incidence of atypical tubule hyperplasia and renal tubule tumors (RTT). The likely cause underlying this association with tubule neoplasia is the long-term increased tubule cell proliferation that occurs throughout CPN progression. As a variety of chemicals are able to exacerbate CPN, there is a potential for those exacerbating the severity up to and including end-stage kidney to cause a marginal increase in RTT and their precursor lesions. Extensive statistical analysis of National Toxicology Program studies shows a strong correlation between high-grade CPN, especially end-stage CPN, and renal tumor development. CPN as a mode of action (MOA) for rat RTT has received attention from regulatory authorities only recently. In the absence of toxic effects elsewhere, this does not constitute a carcinogenic effect of the chemical but can be addressed through a proposed MOA approach for regulatory purposes to reach a decision that RTT, developing as a result of CPN exacerbation in rats, have no relevance for human risk assessment. Guidelines are proposed for evaluation of exacerbation of CPN and RTT as a valid MOA for a given chemical.

Tobacco particulate matter is more potent than nicotine at upregulating nicotinic receptors on SH-SY5Y cells.

The effect of total particulate matter (TPM) from cigarette smoke on the expression and binding properties of nicotinic acetylcholine receptors (nAChRs) was investigated using a human neuroblastoma cell line (SH-SY5Y). TPM but not nicotine on its own inhibited cell growth at nicotine concentrations above 5 microM. To examine effects on nAChR expression, intact cells were incubated with 3H-epibatidine, and a Bmax of 13 fmoles/10(5) cells (7.8 x 10(4) binding sites/cell) was measured in unexposed cells as well as in cells treated with 2 microM nicotine alone or with TPM containing 2 microM nicotine. Using Scatchard analysis, we measured a Kd of 0.3 nM for 3H-epibatidine binding to nAChRs. This Kd was increased to 1.3 nM by addition of nicotine or TPM extract, both at 2 microM nicotine. Bmax, however, was unaffected, suggesting competitive binding of nicotine to its receptor. Short-term and prolonged 3-day exposures of SH-SY5Y cells to either TPM or nicotine at nicotine concentrations ranging from 0.2 microM to 20 microM increased specific binding, suggesting upregulation of nAChR expression. Most significant, binding was consistently greater in cells pretreated with TPM than in cells pretreated with nicotine. We conclude that TPM contains compounds that are toxic to cells at high concentrations (cell growth inhibition) but that do not compete with nicotine for binding to nAChRs (Scatchard analysis). These non-nicotinic compounds are capable of increasing the expression of one or more of the nAChR subunits. Furthermore, our cell culture assay provides a useful in vitro model for assessing the relative addictiveness of different tobacco products, including that of non-nicotine components.

A benchmark dose analysis for sodium monofluoroacetate (1080) using dichotomous toxicity data.

The use of a benchmark dose (BMD) as an alternative to a no-observed-adverse-effect-level (NOAEL) approach was investigated as a means to improve current risk assessment values of sodium monofluoroacetate (1080). The feasibility of implementing the two approaches was investigated for three critical toxicological end points, namely cardiomyopathy, testicular toxicity and teratogenic effects identified from the few available critical studies. The BMD provides better representation of the dose-response relationship, offering an advantage over the current NOAEL approach. The calculated BMDs and lower-bound confidence limits (BMDLs) for the three end points were estimated using the Weibull, probit and quantal linear models for each end point. All models passed the chi2 test statistics (p > or = 0.1) for all three toxicity endpoints tested. A benchmark response (BMR) of 10% (extra risk) was chosen and the Akaike's information criterion (AIC) was used in selecting the appropriate model. The BMDL estimates derived were found to be generally slightly higher but comparable to the NOAEL for those same endpoints. The BMD(10) and BMDL(10) for cardiomyopathy and testicular effects were 0.21 mgkg(-1) bw and 0.10 mgkg(-1) bw, respectively. These values are proposed for use in the eventual determination of the tolerable daily intake (TDI) for 1080.