R. Steven Pappas

Establishment of Toxic Metal Reference Range in Tobacco from US Cigarettes

Smoking remains the leading cause of preventable death in the United States. There are numerous harmful substances in tobacco and tobacco smoke. Among the more than 4,000 identified compounds in smoke, many metals contribute to the health risks associated with tobacco use. Specific metals found in tobacco and tobacco smoke have been classified as carcinogens by the International Agency for Research on Cancer. Exposure to toxic metals can cause outcomes including inflammation, sensitization and carcinogenesis. Metals in tobacco are transported in tobacco smoke proportionally with their concentrations in tobacco filler for a given cigarette design. To quantitatively examine the metal content in numerous tobacco products, high throughput methods are desired. This study developed a simple, rapid tobacco digestion method coupled with a sensitive analytical method using inductively coupled plasma-mass spectrometry. Because of known memory effects and volatility of mercury, quantitative determinations of mercury were made with a direct combustion analyzer. The methods were utilized to examine arsenic, beryllium, cadmium, chromium, cobalt, lead, manganese, mercury and nickel contents in cigarette tobacco and to establish a reference range for the metals in 50 varieties of cigarettes available in the US. These results are comparable to the limited data sets reported by others and with available standard reference material values.

Toxic Metal Concentrations in Mainstream Smoke from Cigarettes Available in the USA

Public health officials and leaders of 168 nations have signaled their concern regarding the health and economic impacts of smoking by becoming signatory parties to the World Health Organization Framework Convention on Tobacco Control (FCTC). One of FCTCs purposes is to help achieve meaningful regulation for tobacco products in order to decrease the exposure to harmful and potentially harmful constituents (HPHCs) delivered to users and those who are exposed to secondhand smoke. Determining baseline delivery ranges for HPHCs in modern commercial tobacco products is crucial information regulators could use to make informed decisions. Establishing mainstream smoke delivery concentration ranges for toxic metals was conducted through analyses of total particulate matter (TPM) collected with smoking machines using standard smoking regimens. We developed a rapid analytical method with microwave digestion of TPM samples obtained with smoking machines using electrostatic precipitation under the ISO and Intense smoking regimens. Digested samples are analyzed for chromium, manganese, cobalt, nickel, arsenic, cadmium and lead using inductively coupled plasma-mass spectrometry. This method provides data obtained using the ISO smoking regimen for comparability with previous studies as well as an Intense smoking regimen that represents deliveries that fall within the range of human exposure levels to toxic metals.

A practical approach to determination of low concentration uranium isotope ratios in small volumes of urine

Thermal ionization-mass spectrometry (TIMS) has long been the benchmark technique for determining uranium isotope ratios. Instrumentation improvements and application optimizations on inductively coupled plasma-mass spectrometry (ICP-MS) instruments have enabled acquisition of data approaching the accuracy and precision obtained using TIMS. However, problems remain for urine uranium ICP-MS isotope ratio analyses at low concentrations. Microwave digestion of urine to eliminate organic interferences, solid phase chelation extraction of actinides from the matrix, use of a desolvating introduction system, and gas flow optimizations to minimize mass fractionation were employed to develop a magnetic sector ICP-MS method sensitive enough to accurately measure urine uranium isotope ratios at concentrations below 10 ng L−1 in 2 mL urine with little or no correction. This method was used to determine isotope ratios for internally and externally prepared natural and depleted uranium-spiked urine. Ratio accuracy obtained from triplicate digestions, preparations, and analyses were within 1% of expected values characterized or calculated from sources over concentrations ranging from 5 to 500 ng L−1 total uranium.

Analysis of total arsenic, total selenium and total chromium in urine by inductively coupled plasma-dynamic reaction cell-mass spectrometry

An accurate and simple method for the determination of total arsenic, total selenium and total chromium in urine has been developed using inductively coupled argon plasma-dynamic reaction cell-mass spectrometry (ICP-DRC-MS). Determination was by external calibration, using matrix-matched standards and high purity calibration materials from a commercial vendor. Aliquots of each urine specimen were diluted (1 + 9) with 2% (v/v) nitric acid containing rhodium and iridium as an internal standard. Argon cell gas was used to remove the isobaric interferences that normally adversely affect 75As, 78Se and 52Cr analysis by ICP-MS and require the use of a dynamic reaction cell (DRC). The principle isobars that interfere with these measurements are [40Ar35Cl]+, [40Ar38Ar]+ and [40Ar12C]+ for 75As, 78Se and 52Cr, respectively. The counts at m/z 75 (arsenic); 78 (selenium); 52 (chromium), 103 (rhodium), and 193 (iridium) were measured. The ratios of the counts at m/z 75 or 78 to those at m/z 193, and m/z 52 to those at m/z 103 were calculated. These ratios were compared with those from urine-based calibration standards to calculate the arsenic, selenium, and chromium concentrations in unknown specimens. The concentrations of arsenic, selenium, and chromium were calculated as μg L−1 in the sample. No creatinine corrections were made, although these could easily be made with data for urine creatinine for each specimen. The proposed method uses the same diluted urine solutions prepared for conventional ICP-MS toxic metal biomonitoring and chemical terrorism screening analysis with the same internal standards; and uses argon as the DRC cell gas. The proposed method provides the basis for an accurate method for determining total arsenic, total selenium, and total chromium in unexposed subjects, and in persons considered to be exposed to those elements through chemical terrorism, environmental, nutritional or other pathways. Approximately 100 specimens, including blanks, calibration standards and quality-control materials, can be processed in an 8 h day.

Biomarkers of exposure to new and emerging tobacco delivery products

Accurate and reliable measurements of exposure to tobacco products are essential for identifying and confirming patterns of tobacco product use and for assessing their potential biological effects in both human populations and experimental systems. Due to the introduction of new tobacco-derived products and the development of novel ways to modify and use conventional tobacco products, precise and specific assessments of exposure to tobacco are now more important than ever. Biomarkers that were developed and validated to measure exposure to cigarettes are being evaluated to assess their use for measuring exposure to these new products. Here, we review current methods for measuring exposure to new and emerging tobacco products, such as electronic cigarettes, little cigars, water pipes, and cigarillos. Rigorously validated biomarkers specific to these new products have not yet been identified. Here, we discuss the strengths and limitations of current approaches, including whether they provide reliable exposure estimates for new and emerging products. We provide specific guidance for choosing practical and economical biomarkers for different study designs and experimental conditions. Our goal is to help both new and experienced investigators measure exposure to tobacco products accurately and avoid common experimental errors. With the identification of the capacity gaps in biomarker research on new and emerging tobacco products, we hope to provide researchers, policymakers, and funding agencies with a clear action plan for conducting and promoting research on the patterns of use and health effects of these products.

Cigarette Smoke Cadmium Breakthrough From Traditional Filters: Implications for Exposure

Cadmium, a carcinogenic metal, is highly toxic to renal, skeletal, nervous, respiratory and cardiovascular systems. Accurate and precise quantification of mainstream smoke cadmium levels in cigarette smoke is important because of exposure concerns. The two most common trapping techniques for collecting mainstream tobacco smoke particulate for analysis are glass fiber filters and electrostatic precipitators. We observed that a significant portion of total cadmium passed through standard glass fiber filters that are used to trap particulate matter. We therefore developed platinum traps to collect the cadmium that passed through the filters and tested a variety of cigarettes with different physical parameters for quantities of cadmium that passed though the filters. We found <1% cadmium passed through electrostatic precipitators. In contrast, cadmium that passed through 92 mm glass fiber filters on a rotary smoking machine was significantly higher, ranging from 3.5 to 22.9% of total smoke cadmium deliveries. Cadmium passed through 44 mm filters typically used on linear smoking machines to an even greater degree, ranging from 13.6 to 30.4% of the total smoke cadmium deliveries. Differences in the cadmium that passed through from the glass fiber filters and electrostatic precipitator could be explained in part if cadmium resides in the smaller mainstream smoke aerosol particle sizes. Differences in particle size distribution could have toxicological implications and could help explain the pulmonary and cardiovascular cadmium uptake in smokers.

Simple changes improve sample throughput for determination of low concentration uranium isotope ratios in small volumes of urine

An increase in the solid phase extraction column wash volume, change of internal standard, magnet mass, and use of an instrumental mass offset has permitted the elimination of digestion and cutting the sample preparation time of the previously published method in half (50 min) without cost to 235U/238U ratio accuracy.

High-Throughput Determination of Mercury in Tobacco and Mainstream Smoke from Little Cigars

A method was developed that utilizes a platinum trap for mercury from mainstream tobacco smoke, which represents an improvement over traditional approaches that require impingers and long sample preparation procedures. In this approach, the trapped mercury is directly released for analysis by heating the trap in a direct mercury analyzer. The method was applied to the analysis of mercury in the mainstream smoke of little cigars. The mercury levels in little cigar smoke obtained under Health Canada Intense smoking machine conditions ranged from 7.1 × 10(-3) to 1.2 × 10(-2) mg/m(3). These air mercury levels exceed the chronic inhalation minimal risk level corrected for intermittent exposure to metallic mercury (e.g., 1 or 2 h per day, 5 days per week) determined by the Agency for Toxic Substances and Disease Registry. Multivariate statistical analysis was used to assess associations between mercury levels and little cigar physical design properties. Filter ventilation was identified as the principal physical parameter influencing mercury concentrations in mainstream little cigar smoke generated under ISO machine smoking conditions. With filter ventilation blocked under Health Canada Intense smoking conditions, mercury concentrations in tobacco and puff number (smoke volume) were the primary physical parameters that influenced mainstream smoke mercury concentrations.

Electrothermal Vaporization-QQQ-ICP-MS for Determination of Chromium in Mainstream Cigarette Smoke Particulate

Chromium is transported in mainstream tobacco smoke at very low concentrations. However, when chromium is deposited too deeply in the lungs for mucociliary clearance, or is in a particle that is too large to pass directly through tissues, it bioaccumulates in the lungs of smokers. It is important to determine the concentrations of chromium that are transported in mainstream smoke. Several reliable studies have resulted in reports of chromium concentrations in smoke particulate that were below limits of detection (LODs) for the instruments and methods employed. In this study, electrothermal vaporization-triple quad-inductively coupled plasma-mass spectrometry (ETV-QQQ-ICP-MS) was chosen for determination of chromium concentrations in mainstream smoke because of the high sensitivity of ETV combined with QQQ-ICP-MS. The smoke from five reference, quality control, and commercial cigarettes was analyzed using ETV-QQQ-ICP-MS with isotope dilution for quantitative determination of chromium. The method LOD was sufficiently low that chromium concentrations in mainstream smoke could indeed be determined. The chromium concentrations in the smoke particulate were between 0.60 and 1.03 ng/cigarette. The range of chromium concentrations was at or below previously reported LODs. Determination of the oxidation state of the chromium transported in mainstream smoke would also be important, in consideration of the fact that both chromium(III) and chromium(VI) oxidation states cause inhalation toxicity, but chromium(VI) is also a carcinogen. It was possible to separate the oxidation states using ETV-QQQ-ICP-MS. However, determination of individual species at the levels found in mainstream smoke particulate matter was not possible with the present method.

Electron Microscopic Analysis of Surface Inorganic Substances on Oral and Combustible Tobacco Products

Although quantitative trace toxic metal analyses have been performed on tobacco products, little has been published on inorganic particulate constituents on and inside the products. We analyzed these constituents using scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS). The nature of SEM-EDS instrumentation makes it an ideal choice for inorganic particulate analyses and yields relevant information to potential exposures during consumption of oral tobacco products, and possibly as a consequence of smoking. Aluminum silicates, silica and calcium compounds were common inorganic particulate constituents of tobacco products. Aluminum silicates and silica from soil were found on external leaf surfaces. Phytolithic silica, found in the lumen of the plant leaf, is of biogenic origin. Calcium oxalate was also apparently of biogenic origin. Small mineral deposits on tobacco could have health implications. Minerals found on the surfaces of smokeless tobacco products could possibly abrade the oral mucosa and contribute to the oral inflammatory responses observed with smokeless tobacco product use. If micron and sub-micron size calcium particles on cigarette filler were transported in mainstream smoke, they could potentially induce a pulmonary irritant inflammation when inhaled. The transport of aluminum silicate and silica in smoke could potentially also contribute to chronic inflammatory disease.