Lactic Acid Salts of Nicotine Potentiate the Transfer of Toxic Metals into Electronic Cigarette Aerosols.

The designs and liquid formulations of Electronic Nicotine Delivery System (ENDS) devices continue to rapidly evolve. Thus, it is important to monitor and characterize ENDS aerosols for changes in toxic constituents. Many ENDS liquid formulations now include the addition of organic acids in a 1 to 1 molar ratio with nicotine. Metal concentrations in aerosols produced by ENDS devices with different nicotine salt formulations were analyzed. Aerosols from devices containing lactic acid had higher nickel, zinc, copper, and chromium concentrations than aerosols produced by devices containing benzoic acid or levulinic acid. Our scanning electron microscope with energy dispersive X-ray analytical findings showed that the metals determined in the inductively coupled plasma-mass spectrometry analytical results were consistent with the metal compositions of the ENDS device components that were exposed to the liquids and that nickel is a major constituent in many ENDS internal components. As a result of the exposure of the nickel-containing components to the ENDS liquids, resulting aerosol nickel concentrations per puff were higher from devices that contained lactic acid in comparison to devices with benzoic or levulinic acid. The aerosol nickel concentrations in 10 puffs from ENDS-containing lactic acid were, in some cases, hundreds of times higher than cigarette mainstream smoke nickel deliveries. Thus, the design of an ENDS device in terms of both physical construction components and the liquid chemical formulations could directly impact potential exposures to toxic constituents such as metals.

Toxic Metals in Liquid and Aerosol from Pod-Type Electronic Cigarettes.

High-quality, accurate data on liquid contents and aerosol emissions from electronic nicotine delivery systems (ENDS, e.g., e-cigarettes) are crucial to address potential health concerns as these devices evolve and mature. Metals are an important class of ENDS constituents that merit attention as they have various health implications. Proper sampling, handling and aerosol trapping materials are essential to generate accurate quantitative metal data and to reduce the likelihood of inaccurate results originating from inappropriate collection vessels and materials that contribute to high background levels. Published methods that meet these criteria were applied to the analyses of chromium, nickel, copper, zinc, cadmium, tin and lead in liquid and aerosol from mint/menthol and tobacco flavors of currently popular pod-based devices from three manufacturers. Metal concentrations from pods that had not been used for generating aerosol ranged from below our lowest reportable level to 0.164 µg/g for Cr, 61.3 µg/g for Ni, 927 µg/g for Cu, 14.9 µg/g for Zn, 58.2 µg/g for Sn and 2.56 µg/g for Pb. Cadmium was included in our analyte panel and was not present above detection limits in liquid or aerosol. Aerosol metal concentrations (using a 55-mL puff) ranged from below our lowest reportable level to 29.9 ng/10 puffs for Cr, 373 ng/10 puffs for Ni, 209 ng/10 puffs for Cu, 4,580 ng/10 puffs for Zn, 127 ng/10 puffs for Sn and 463 ng/10 puffs for Pb. Our results showed some metal delivery from all the products examined and highly variable metal levels between manufacturer, brand and package.

Analysis of Toxic Metals in Aerosols from Devices Associated with Electronic Cigarette, or Vaping, Product Use Associated Lung Injury.

Research gaps exist in toxic metals characterization in e-cigarette, or vaping, products (EVPs) as these analytes typically have low concentrations and most standard aerosol trapping techniques have high metals background. An additional complication arises from differences in the EVP liquid formulations with nicotine products having polar properties and non-nicotine products often being non-polar. Differences in polar and non-polar matrices and the subsequent aerosol chemistries from various EVPs required modifications of our previously reported nicotine-based EVP aerosol method. Validation and application of the expanded method, suitable for both hydrophobic and hydrophilic aerosols, are reported here. The metals analyzed for this study were Al, Cr, Fe, Co, Ni, Cu, Cd, Sn, Ba, and Pb. The method limits of detection for the modified method ranged from 0.120 ng/10 puffs for Cd to 29.3 ng/10 puffs for Al and were higher than reported for the previous method. Results of the analyses for metals in aerosols obtained from 50 EVP products are reported. Cannabinoid based EVP aerosols were below reportable levels, except for one sample with 16.08 ng/10 puffs for Cu. Nicotine-based EVP results ranged from 6.72 ng/10 puffs for Pb to 203 ng/10 puffs for Sn. Results of the analyses for these metals showed that aerosols from only 5 of the 50 devices tested had detectable metal concentrations. Concentrations of toxic elements in the aerosols for nicotine-based EVP aerosol metal concentration ranges were consistent with previously published results of aerosol analyses from this class of devices.

Toxic Metal-Containing Particles in Aerosols from Pod-Type Electronic Cigarettes.

The popularity of electronic cigarettes (electronic nicotine delivery systems or ENDS) has grown rapidly over the past decade. With the continued evolution of ENDS, and the arrival of newer replaceable pod devices on the market, it is prudent to examine their emissions to help determine potential health risks to the user. Metal-containing particles were examined in aerosol from several pod-based devices from three manufacturers that offer flavored liquids in their respective products. Previous ENDS metal emissions studies focused on the total toxic metal concentrations in aerosols and have suggested that the principal sources are oxidized internal metal components that are in contact with the liquid. Most metal oxides have limited solubility, and it is likely that some metal content in ENDS aerosol may present as particles rather than dissolved forms. Examining the composition and number of particles in the ENDS aerosols is important because inhaled metal oxide particles cause pulmonary inflammation. Chronic inhalation of ENDS aerosol may lead to inflammatory cell activation in the lungs. Therefore, this study was designed to measure metal oxide particle concentrations and sizes in ENDS aerosols from select pod-based systems. Aerosol samples were generated with pod liquids (tobacco, mint or menthol) from devices produced by three manufacturers using CORESTA Recommended Method 81 parameters with a high-purity fluoropolymer aerosol trap. Particle sizes for chromium, iron, nickel, copper, zinc, tin and lead oxides were measured in triplicate using single particle inductively coupled plasma-mass spectrometry and dynamic light scattering. A novel aspect of these measurements included using dual element particle analysis to infer particle source component material. Particle concentrations in aerosols from the devices were variable between devices and from pod to pod, ranging from no detectable chromium- and zinc-containing particles in aerosol from some pods to 222,000 lead containing particles per 10 puffs from individual pods.

Analysis of Toxic Metals in Electronic Cigarette Aerosols Using a Novel Trap Design.

Since 2006 the domestic popularity and sales of electronic cigarettes (i.e., electronic nicotine delivery systems or ENDS) have grown rapidly. Although the constituents of the aerosol produced by ENDS have been previously investigated, differences in puff regimens and aerosol trapping schema in published literature often complicate result comparisons and data interpretation. As the ENDS product designs continue to evolve, there is a critical need to develop and validate robust methodologies for laboratory testing, appropriate aerosol generation and trapping media required for accurate determinations of ENDS aerosol metals deliveries. A simple, high metals purity, fluoropolymer trap was developed and validated that meets standard machine puffing regimen (CORESTA Recommended Method 81) specifications and exhibits negligible acid extractable metal backgrounds. Using a standard machine puffing regimen in combination with a fluoropolymer condensation trap, aerosol was generated and collected from select ENDS devices for analysis of chromium, nickel, copper, zinc, cadmium, tin, and lead with triple quadrupole inductively coupled plasma mass spectrometry. Devices tested spanned a range of commercial products, including flavored variants of JUUL pods, refillable tank systems, rechargeable cartridges, and single-use ENDs devices. Results showed that for aerosols generated under a fixed puffing regimen (50 puffs/collection), metal concentrations ranged from below the detection limits (LOD) to 614 ng copper and 339 ng zinc per 10 puffs. Cadmium concentrations were below LOD for all devices tested. Device specific aerosol levels of Sn and Pb ranged from below LOD to low nanogram levels. Cr and Ni were transported in aerosols at levels equivalent to, or slightly higher than in mainstream cigarette smoke using a standard smoking regimen. The generally lower levels of specific metals, Cd and Pb, transmitted in ENDS aerosols compared to mainstream cigarette smoke reflect possible reduction of harm for smokers who substitute the use of ENDS as cessation devices in place of smoking cigarettes.

Analysis of Toxic Metals in Liquid from Electronic Cigarettes.

As the technology of electronic nicotine delivery systems (ENDS), including e-cigarettes, evolves, assessing metal concentrations in liquids among brands over time becomes challenging. A method for quantification of chromium, nickel, copper, zinc, cadmium, tin, and lead in ENDS liquids using triple quadrupole inductively coupled plasma mass spectrometry was developed. The method's limits of detection (LODs) were 0.031, 0.032, 3.15, 1.27, 0.108, 0.099, 0.066 µg/g for Cr, Ni, Cu, Zn, Cd, Sn, and Pb respectively. Liquids analyzed were from different brands and flavors of refill bottles or single-use, rechargeable, and pod devices from different years. Scanning electron microscopy with energy dispersive spectroscopy further evaluated the device components' compositions. Refill liquids before contacting a device were below lowest reportable levels (LRL) for all metals. Copper and zinc were elevated in liquids from devices containing brass. Cadmium was

Electron Microscopic Analysis of Silicate and Calcium Particles in Cigarette Smoke Tar.

Scanning electron microscopy with energy dispersive x-ray spectroscopy (SEM-EDS) supplies information that is complementary to those data traditionally obtained using inductively coupled plasma-mass spectrometry for analysis of inorganic tobacco and tobacco smoke constituents. The SEM-EDS approach was used to identify select inorganic constituents of mainstream cigarette smoke "tar." The nature of SEM-EDS instrumentation makes it an ideal choice for microstructural analyses as it provides information relevant to inorganic constituents that could result from exposure to combusted tobacco products. Our analyses show that aluminum silicates, silica, and calcium compounds were common constituents of cigarette mainstream smoke "tar." Identifying inorganic tobacco smoke constituents is important because inhalation of fine inorganic particles could lead to inflammatory responses in the lung and systemic inflammatory responses. As cigarette smoking causes chronic inflammation in the respiratory tract, information on inorganic particulate in mainstream smoke informs efforts to determine causative agents associated with increased morbidity and mortality from tobacco use.

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.

Stream depletion in alluvial valleys using the SDF semianalytical model.

A semianalytical method commonly used for quantifying stream depletion caused by ground water pumping was reviewed for applicability in narrow alluvial aquifers. This stream depletion factor (SDF) method is based on the analytic Glover model, but uses a numerical model-derived input parameter, called the SDF, to partly account for mathematically nonideal conditions such as variable transmissivity and nearby aquifer boundaries. Using the SDF can improve and simplify depletion estimates. However, the method's approximations introduce error that increases with proximity to the impermeable aquifer boundary. This article reviews the history of the method and its assumptions. New stream depletion response curves are presented as functions of well position within bounded aquifers. A simple modification to modeled SDF values is proposed that allows the impermeable boundary to be accounted for with image wells, but without overaccounting for boundary effects that are already reflected in modeled SDFs. It is shown that SDFs for locations closer to the river than to the aquifer boundary do not reflect impermeable-boundary effects, and thus need no modification, and boundary effects in the other portion of the aquifer follow a predictable removable pattern. This method is verified by comparing response curves using modified SDFs with response curves from an extensively calibrated numerical model of a managed ground water recharge site. The modification improves SDF-based stream depletion estimates in bounded aquifers while still benefiting from the additional information contained in SDF maps and retaining their value as standardized references for water rights administration.