Aerosol Droplet Size Research Articles

Supersaturation Fluctuations during the Early Stage of Cumulus Formation

Abstract On time scales that are long compared to the phase relaxation time, a quasi-steady supersaturation sqs is expected to exist in clouds. On shorter time scales, however, turbulent fluctuations of temperature and water vapor concentration should generate fluctuations in supersaturation. The variability of temperature, water vapor, and supersaturation has been measured in situ with submeter resolution in warm, continental, shallow cumulus clouds. Several cumuli with horizontal extents of order 100 m were sampled during their first appearance and development to depths of ~100 m in a growing boundary layer. Fluctuations of the saturation ratio are observed to be approximately normally distributed with standard deviations on the order of 1%. This variability is almost one order of magnitude larger than sqs calculated using simultaneous measurements of the vertical velocity component and the droplet size distribution. It is argued that, depending on the ratio of the phase relaxation and the turbulent mixing time, substantial fluctuations in the supersaturation field can exist on small spatial scales, centered on sqs for the mean state. The observations also suggest that, on larger scales, fluctuations of the supersaturation field are damped by cloud droplet growth. Droplets with diameters of up to 20 μm were observed in the shallow cumulus clouds, whereas the adiabatic diameter was less than 10 μm. Such large droplets may be explained by a few droplets experiencing the highest observed supersaturations for a certain time. Consequences for aerosol activation and droplet size dispersion in a highly fluctuating supersaturation field are briefly discussed.

Transient flashing propellant flow models to predict internal flow characteristics, spray velocity, and aerosol droplet size of a pMDI

ABSTRACTDespite the popularity of the pMDI as an asthma remedy, the mechanism leading to spray generation is elusive, mainly due to small length scales and short time scale, causing experimental difficulties to obtain flow information. This mechanism involves transient development of two-phase flashing propellant flow inside pMDI actuator as well as transfer of heat, mass, and momentum between the liquid and vapor phase. Variations in the rate of such interphase phenomena dictate the two-phase mass flow rate emission, which itself determines spray velocity and droplet size. In this work, we compare the performance of existing two-phase flow models to predict the flow conditions and the rate of propellant flow through a pMDI actuator: the homogenous equilibrium model (HEM), the slip equilibrium model (SEM), and the homogenous frozen model (HFM). The velocity prediction of the HFM was found to be in good agreement with phase Doppler anemometry (PDA) data indicating the metastable nature of the emitted prope...

Brownian coagulation of a bi-modal distribution of both spherical and fractal aerosols

The use of Global Circulation Models (GCM) or mesoscale models are now widely used to understand planetary climatic systems. The increasing complexity of the models and the more and more detailed observations of the planetary bodies necessitate a corresponding increase in the complexity of the physical processes which are included in these models. In all the planetary atmospheres in the solar system, aerosols and clouds can be found and therefore microphysical processes must be included in climate models. The most accurate models are those where aerosol and cloud droplet size distributions are described with bins. This type of sophisticated and accurate models only needs a small quantity of a priori information to be used. However, they are demanding in computational resource. They can only be used in GCM at the cost of very long, and sometime prohibitive, time of computation. Alternatively, an other class of microphysical models, based on the description of the aerosol and cloud distributions with moments of distribution can be used. But, they need first to be developed and compared with a more detailed model and they need an a priori information about the size distributions.In this article, we describe the development of the microphysical equations to treat the interaction of two populations of aerosols, with different geometrical structures, written with moment of distributions, interacting through Brownian coagulation. This problem was solved specifically for the case of Titan, the larger satellite of Saturn, where small aerosols have a spherical shape, large aerosols have a fractal aggregated structure and where aerosols bear an electric charge. The two populations interact in the mesosphere. The fractal structure of the large aerosols also has a consequence on the shape of the size distribution and on the laws of the microphysics that must be accounted a priori in the method. The case of Titan is probably one of the most complex and, in this work, we have written the set of equations in the most general way so they can be used for any other cases. Once developed, we finally compare the results yielded by our new model with the results obtained with the classical model based on a description in bins.

Estimation size of aerosol droplets produced by explosion

Estimation size of aerosol droplets produced by explosion

A scattering methodology for droplet sizing of e-cigarette aerosols

Context: Knowledge of the droplet size distribution of inhalable aerosols is important to predict aerosol deposition yield at various respiratory tract locations in human. Optical methodologies are usually preferred over the multi-stage cascade impactor for high-throughput measurements of aerosol particle/droplet size distributions.Objective: Evaluate the Laser Aerosol Spectrometer technology based on Polystyrene Sphere Latex (PSL) calibration curve applied for the experimental determination of droplet size distributions in the diameter range typical of commercial e-cigarette aerosols (147–1361 nm).Materials and methods: This calibration procedure was tested for a TSI Laser Aerosol Spectrometer (LAS) operating at a wavelength of 633 nm and assessed against model di-ethyl-hexyl-sebacat (DEHS) droplets and e-cigarette aerosols. The PSL size response was measured, and intra- and between-day standard deviations calculated.Results: DEHS droplet sizes were underestimated by 15–20% by the LAS when the PSL calibration curve was used; however, the intra- and between-day relative standard deviations were < 3%. This bias is attributed to the fact that the index of refraction of PSL calibrated particles is different in comparison to test aerosols. This 15–20% does not include the droplet evaporation component, which may reduce droplet size prior a measurement is performed. Aerosol concentration was measured accurately with a maximum uncertainty of 20%. Count median diameters and mass median aerodynamic diameters of selected e-cigarette aerosols ranged from 130–191 nm to 225–293 nm, respectively, similar to published values.Discussion and conclusion: The LAS instrument can be used to measure e-cigarette aerosol droplet size distributions with a bias underestimating the expected value by 15–20% when using a precise PSL calibration curve. Controlled variability of DEHS size measurements can be achieved with the LAS system; however, this method can only be applied to test aerosols having a refractive index close to that of PSL particles used for calibration.

Technical description of the microinjection pump (MIP®) and granulometric characterization of the aerosol applied for pressurized intraperitoneal aerosol chemotherapy (PIPAC).

Pressurized intraperitoneal aerosol chemotherapy (PIPAC) is gaining acceptance in clinical practice, but detailed information about the microinjection pump (MIP®), the generated aerosol and drug distribution is missing. Ex vivo granulometric analyses by means of laser diffraction spectrometry were performed for MIP® aerosol characterization. Beside the standard operation conditions, the impact of the volumetric liquid flow rate on the aerosol characteristics was investigated with different liquids. Granulometric results as well as the local drug distribution were verified by ex vivo gravimetric analyses. On the basis of determined MIP® characteristics, the aerosol droplet size, which is necessary for a homogenous intra-abdominal drug distribution, was calculated. Granulometric analyses showed that the MIP® aerosol consists of a bimodal volume-weighted particle size distribution (PSD3) with a median droplet diameter of x 50,3=25µm. Calculations reveal that the droplet size for a homogenous intra-abdominal drug distribution during PIPAC therapy should be below 1.2µm. We show that >97.5vol% of the aerosolized liquid is delivered as droplets with ≥3µm in diameter, which are primarily deposited on the surface beneath the MIP® by gravitational settling and inertial impaction. These findings were confirmed by ex vivo gravimetric analyses, where more than 86.0vol% of the aerosolized liquid was deposited within a circular area with a diameter of 15cm. The granulometric aerosol properties, as well as the aerodynamic conditions achieved by standard MIP® operation, do not support the idea of widespread or homogenous drug distribution in the abdominal cavity.

Aerosol Flow in the Vitrocell 24/48 Exposure System: Flow Mixing and Aerosol Coalescence

In vitro exposure systems are increasingly used in modern toxicology assessment studies. An understanding of the functioning of these complex systems and their characterization ensures well-controlled delivery of substances to cell cultures and reliable biological response of cells to the given external conditions. In this work, we present the flow-mixing efficiency of the dilution unit in the Vitrocell® 24/48 (VC24/48) exposure system, together with the role of thermal coalescence. We adopted a computational fluid dynamics approach with integrated aerosol dynamics to analyze the dilution system using high-resolution simulations. We performed simulations for three total flow rates through the system: 3, 6, and 12 L/min, to investigate the influence of turbulent mixing and thermal coalescence on the aerosol characteristics. We found that for all simulated flow rates, instantaneous and localized turbulent mixing is induced by the two opposing dilution jets. We found the aerosol to be uniformly mixed and the flow to be laminarized upstream of the location of the first aerosol sampling trumpet. In summary, the design of the double-tee junction, serving as the dilution unit of the VC24/48 system, guarantees efficient and localized mixing/dilution of the aerosol, while still delivering laminar flow toward deposition wells, when operated under these high flow-rate conditions. In addition, we showed that thermal coalescence effects do not influence the aerosol droplet size distribution during the dilution process for the studied simulation conditions.

Influence of amine-modified poly(vinyl alcohol)s on vibrating-membrane nebulizer performance and lung toxicity

A suitable aerosol droplet size and formulation output rate is essential for the therapy of lung diseases under application of nebulizers. The current study investigated the potential of amine-modified poly(vinyl alcohol)s as excipients for inhalation delivery.A change of conductivity (effective at <0.1mg/ml) and viscosity (effective at >0.1mg/ml) of samples that were supplemented with charge-modified polymers had a significant influence on the generated droplet size (shift from ~8 to ~4μm) and formulation throughput rate (shift from ~0.2 to ~1.0g/min), where polymers with a higher amine density (and molecular weight) showed an elevated activity. Biocompatibility assessment of polymers in A549 cells and an isolated lung model resulted in cell lysis and lung edema formation dependent on the type (degree of amine substitution) and dose of polymer applied.Suitable compositions and concentrations of amine-modified poly(vinyl alcohol)s were identified with respect to an optimized nebulizer performance and acceptable biocompatibility. Charge-modified polymers represent novel excipients with potential to improve inhalation therapy.

Improved electrospray design for aerosol generation and flame propagation analysis

Although the hazards of aerosol fires and explosions have been studied for decades the data for aerosol flame propagation is still scarce. Additionally there is a lack of standard techniques and measurement apparatus, which impedes the development of optimal aerosol hazard mitigation measures. The focus of this study is development of an improved aerosol electrospray device for the generation of high quality aerosol data. The goal is achieved through higher nozzle packing, precise nozzle and mesh hole alignment and adding two ground meshes. In addition to a flat ground mesh, the utilization of a cylindrical ground mesh demonstrated improved confinement and guidance of droplets. Duratherm 600, heat transfer fluid, was examined to demonstrate the modified electrospray device capabilities as compared to previous design. Results show the modified electrospray can produce more uniform droplets, more even test chamber dispersion, smaller droplet size and higher concentration aerosol, which is essential to study aerosol flame propagation. Accordingly, the results of aerosol flame speed tests for the improved design were more reproducible. Moreover, it was found that a traditional propane pilot flame was unable to ignite the smaller aerosol droplet size due to the strong turbulence generated by the open flame. However, by careful modification of the pilot flame length, the turbulence decreased dramatically and the small droplet size aerosol can be tested.

Ionization of solutions using mechanical spray in collison nebulizer: A new simple ion source for mass-spectrometric analysis

Ionization methods for mass-spectrometric analysis based on mechanical liquid spray by a high-speed gas flow (like Sonic Spray Ionization (SSI)) offer some advantages over other ionization methods. Among these one should mention the absence of electric voltage, radioactive sources and heaters. In this paper we suggest using the Collison nebulizer for solution ionization via mechanical spray. Research results into the efficiency of the Collison spray ionization of different solvents used in chemical synthesis are submitted. It is shown that an increase in dipole moment of the solvent molecules leads to increased ionization efficiency for all solvents tested, except water. This seems to result from anomaly high surface tension and vaporization enthalpy for water. High concentrations (>10−4g/ml) of both inorganic salts (NaCl, K2SO4) and organic additive (morphine) give a decrease in the total ion current at the Collison nebulizer outlet. This is assumed to be due both to an increased droplet size of aerosol produced upon spraying and a low dipole moment of an ion-solvation shell complex. Mass-spectra of aqueous K2SO4 and morphine (C17H19NO3) were obtained with the Collison nebulizer. These spectra contained non-identified background peaks along with the peaks of K+ and H+C17H19NO3 that were likely to result from the water ionization and presence of uncontrolled impurities. A relationship between the intensity of mass-spectroscopic peaks of the ions of potassium and morphine and the concentration of appropriate aqueous solution was determined. Mass-spectrometric analysis using the Collison spray ionization gave a detection limit for morphine ∼10−8g/ml and a linear response range for protonated molecular ion (H+C17H19NO3 with m/z=286 from 10−8g/ml to 2×10−7g/ml.

How thermodynamic environments control stratocumulus microphysics and interactions with aerosols

Aerosol–cloud interactions are central to climate system changes and depend on meteorological conditions. This study identifies distinct thermodynamic regimes and proposes a conceptual framework for interpreting aerosol effects. In the analysis, ten years (2003–2012) of daily satellite-derived aerosol and cloud products are combined with reanalysis data to identify factors controlling Southeast Atlantic stratocumulus microphysics. Considering the seasonal influence of aerosol input from biomass burning, thermodynamic environments that feature contrasting microphysical cloud properties and aerosol–cloud relations are classified. While aerosol impact is stronger in unstable environments, it is mostly confined to situations with low aerosol loading (aerosol index AI ≲ 0.15), implying a saturation of aerosol effects. Situations with high aerosol loading are associated with weaker, seasonally contrasting aerosol-droplet size relationships, likely caused by thermodynamically induced processes and aerosol swelling.

Size-dependent particle activation properties in fog during the ParisFog 2012/13 field campaign

Abstract. Fog-induced visibility reduction is responsible for a variety of hazards in the transport sector. Therefore there is a large demand for an improved understanding of fog formation and thus improved forecasts. Improved fog forecasts require a better understanding of the numerous complex mechanisms during the fog life cycle. During winter 2012/13 a field campaign called ParisFog aiming at fog research took place at SIRTA (Instrumented Site for Atmospheric Remote Sensing Research). SIRTA is located about 20 km southwest of the Paris city center, France, in a semi-urban environment. In situ activation properties of the prevailing fog were investigated by measuring (1) total and interstitial (non-activated) dry particle number size distributions behind two different inlet systems; (2) interstitial hydrated aerosol and fog droplet size distributions at ambient conditions; and (3) cloud condensation nuclei (CCN) number concentration at different supersaturations (SS) with a CCN counter. The aerosol particles were characterized regarding their hygroscopic properties, fog droplet activation behavior and contribution to light scattering for 17 developed fog events. Low particle hygroscopicity with an overall median of the hygroscopicity parameter, κ, of 0.14 was found, likely caused by substantial influence from local traffic and wood burning emissions. Measurements of the aerosol size distribution at ambient RH revealed that the critical wet diameter, above which the hydrated aerosols activate to fog droplets, is rather large (with a median value of 2.6μm) and is highly variable (ranging from 1 to 5μm) between the different fog events. Thus, the number of activated fog droplets was very small and the non-activated hydrated particles were found to contribute significantly to the observed light scattering and thus to the reduction in visibility. Combining all experimental data, the effective peak supersaturation, SSpeak, a measure of the peak supersaturation during the fog formation, was determined. The median SSpeak value was estimated to be in the range from 0.031 to 0.046% (upper and lower limit estimations), which is in good agreement with previous experimental and modeling studies of fog.

Laminar mass burning and entrainment velocities and flame instabilities of i-octane, ethanol and hydrous ethanol/air aerosols

The paper reports experiments employing the cloud chamber technique for creating fuel aerosols, in studies of premixed laminar flames. Spherical explosion flames were initiated at different times after the start of expansion of the original gaseous mixture to lower pressure. Flame speeds were measured close to atmospheric pressure, over a range of equivalence ratios of iso-octane, ethanol and hydrous ethanol with air. A methodology was developed for deriving mass burning velocities and entrainment velocities, as well as mass burning fluxes, from the measurements of aerosol number densities, droplet sizes and flame speeds. It was vital to estimate whether droplet evaporation was completed in the flame preheat zone. This was done by calculating the spatial progress of droplet evaporation for the different aerosols from values of the evaporation rate constants of the different fuels.With predominantly the leaner mixtures and smaller droplet diameters, evaporation was close to completion, but the mass burning velocities of the aerosols were somewhat lower than those of the corresponding gaseous phases, because of the lower final temperatures due to the required evaporation enthalpies. However, the mass burning fluxes were higher than those for the purely gaseous flames, due to the higher two-phase reactant densities. At the higher values of the liquid phase equivalence ratio, in overall lean mixtures, the mass burning velocity could exceed that in the purely gaseous phase due to localised enrichment around the droplets.The presence of fuel droplets is shown to enhance the generation of Darrieus–Landau, thermo-diffusive instabilities and the associated flame wrinkling. With richer mixtures and larger droplets, it is possible for droplets to enter the reaction zone and further enhance existing gaseous phase instabilities through the creation of yet further flame wrinkling. This leads to the maximum entrained fuel mass flux, in the richest mixture, being significantly higher than that occurring at the maximum burning velocity of a premixed gaseous flame.

Pilot Plant Activities with Concentrated Piperazine

Amine aerosol testing was conducted at the University of Texas at Austin CO 2 capture pilot plant using concentrated piperazine (3.7 molal) and high temperature flash with cold rich bypass (140 °C). Two methods of piperazine aerosols generation were tested: H2SO4 injection with a liquid vaporizer injector, and direct injection 20 ppm of SO2 into the synthetic flue gas. A Phase Doppler Interferometer (PDI) analyzer from Artium Technologies was used to measure piperazine aerosol droplet sizes and distributions at the absorber gas outlet. A FTIR system with new upgraded heated probes was used to make measurements of total PZ concentrations at the absorber gas inlet and outlet. A manual sampling train method was used to provide secondary validation of FTIR and PDI measurements.

Boosting the aerodynamic properties of vibrating-mesh nebulized polymeric nanosuspensions

Pulmonary application of drug-loaded polymeric nanosuspensions is achieved by vibrating-mesh nebulizers, which allow for an output of intact nanocarriers from the nebulizer reservoir. However, adequate aerosol droplet sizes are a prerequisite for an efficient pulmonary deposition. The current study discloses experimental findings useful to optimize the aerodynamic characteristics of formulations atomized by the vibrating-mesh nebulizers Aeroneb(®) Pro and eFlow(®)rapid. Parameters with significant influence on the aerosol droplet diameter were identified by a statistical design analysis rating size results from laser diffraction. Subsequently, the effect of selected biocompatible solutes on the aerodynamic performance of nebulized formulations was studied and correlated with their physicochemical properties. Vibrating-mesh generated aerosols were significantly affected by the dynamic viscosity and conductivity of the applied formulation. Consequently, an increase in viscosity enhancer (sucrose and poly(ethylene glycol)) or electrolyte (NaCl and CaCl2) content caused the droplet diameter to decrease. Similarly, purified nanosuspensions revealed a considerable decline in aerosol particle size upon excipient addition. However, coating of polymeric nanoparticles with poloxamer and poly(vinyl alcohol) was necessary to avoid electrolyte-induced nanoparticle aggregation. Overall, the current study emphasizes that supplementation of nanosuspensions with biocompatible solutes is an excellent means to tailor the characteristics of aerosols generated by vibrating-mesh technology.

99mTc-labeled therapeutic inhaled amikacin loaded liposomes

The radiolabeling of the liposome surface can be a useful tool for in vivo tracking of therapeutic drug loaded liposomes. We investigated radiolabeling therapeutic drug (i.e. an antibiotic, amikacin) loaded liposomes with 99mTc, nebulization properties of 99mTc-labeled liposomal amikacin for inhalation (99mTc-LAI), and its stability by size exclusion low-pressure liquid chromatography (LPLC). LAI was reacted with 99mTc using SnCl2 dissolved in ascorbic acid as a reducing agent for 10 min at room temperature. The labeled products were then purified by anion exchange resin. The purified 99mTc-LAI in 1.5% NaCl solution was incubated at 4 °C to assess its stability by LPLC. The purified 99mTc-LAI was subjected to studies with a clinically used nebulizer (PARI eFlow®) and the Anderson Cascade Impactor (ACI). The use of ascorbic acid at 0.91 mM resulted in a quantitative labeling efficiency. The LPLC profile showed that the liposomal peak of LAI detected by a UV monitor at both 200 nm and 254 nm overlapped with the radioactivity peak of 99mTc-LAI, indicating that 99mTc-LAI is suitable for tracing LAI. The ACI study demonstrated that the aerosol droplet size distribution determined gravimetrically was similar to that determined by radioactivity. The liposome surface labeling method using SnCl2 in 0.91 mM ascorbic acid produced 99mTc-LAI with a high labeling efficiency and stability that are adequate to evaluate the deposition and clearance of inhaled LAI in the lung by gamma scintigraphy.

New insights in the production of aerosol antibiotics. Evaluation of the optimal aerosol production system for ampicillin-sulbactam, meropenem, ceftazidime, cefepime and piperacillin-tazobactam

Several aerosol antibiotics are on the market and several others are currently being evaluated. Aim of the study was to evaluate the aerosol droplet size of five different antibiotics for future evaluation as an aerosol administration. The nebulizers Sunmist(®), Maxineb(®) and Invacare(®) were used in combination with four different "small <6 ml" residual cups and two "large <10 ml" with different loadings 2-4-6-8 ml (8 ml only for large residual cups) with five different antibiotic drugs (ampicilln-sulbactam, meropenem, ceftazidime, cefepime and piperacillin-tazobactam). The Mastersizer 2000 (Malvern) was used to evaluate the produced droplet size from each combination Significant effect on the droplet size produced the different antibiotic (F=96.657, p<0.001) and the residual cup design (F=68.535, p<0.001) but not the different loading amount (p=0.127) and the nebulizer (p=0.715). Interactions effects were found significant only between antibiotic and residual cup (F=16.736, p<0.001). No second order interactions were found statistically significant. Our results firstly indicate us indirectly that the chemical formulation of the drug is the main factor affecting the produced droplet size and secondly but closely the residual cup design.

Experimental study of mist generated from metalworking fluids emulsions

This paper presents an experimental study of aerosol/mist formed from emulsions of metalworking fluids (MWF) under laboratory conditions. Three different commercial MWFs were investigated at three different oil-in-water emulsion concentrations, 1, 6, and 10% (v/v). The aerosol was generated by novel rotary aerosol generator at a constant rotating speed excluding heat generated by friction. In this way evaporation/condensation mechanism of aerosol generation was minimized. The emulsion was pumped at a constant flow rate. The aerosols characteristics were measured by an optical particle size analyzer. The data for particulate matter less than 2.5μm, (PM2.5), aerosol size distribution, Sauter mean diameter (SD), mass median diameter (MMD) and mass concentration are reported and discussed. Our data show that with increase of the oil concentration in the emulsion, the aerosol droplet sizes increase although the emulsions viscosity does not change significantly.

Challenging the Two-Minute Tidal Breathing Challenge Test

In the adenosine 5'-monophosphate (AMP) bronchial challenge test, AMP is usually administered according to dosing protocols for methacholine. We investigated whether the 2-min tidal breathing challenge test for methacholine is applicable to AMP. Parameters known to affect nebulizer output were studied. Our aim was to determine whether control of additional parameters is needed for currently standardized protocols. The study was performed with the Sidestream nebulizer from the APS Pro Aerosol Provocation System (CareFusion Respiratory). The effects of AMP concentration, jet pressure, and suction flow rate on nebulizer output rate and aerosol droplet size distribution were determined. The volume median diameter for water increased from 5.10 μm to 8.49 μm when the jet pressure was reduced to obtain the prescribed output rate of 0.13 mL/min. The output rate was increased when a suction flow rate was used to remove the aerosol. Increasing the AMP concentration resulted in smaller droplets and a lower output rate when a suction flow was applied. The effects of AMP concentration on nebulizer performance may result in changes in the administered dose and site of deposition of AMP at dose escalation. All of the investigated parameters influence nebulizer performance, hence the outcome of a bronchial challenge test. Therefore, these parameters should not only be specified in challenge testing, but be actively controlled as well.

Nicotine delivery to rats via lung alveolar region-targeted aerosol technology produces blood pharmacokinetics resembling human smoking.

Nicotine is a heavily used addictive drug acquired through smoking tobacco. Nicotine in cigarette smoke is deposited and absorbed in the lungs, which results in a rapidly peaked slowly declining arterial concentration. This pattern plays an important role in initiation of nicotine addiction. A method and device were developed for delivering nicotine to rodents with lung alveolar region-targeted aerosol technology. The dose of delivery can be controlled by the nicotine aerosol concentration and duration of exposure. Our data showed that, in the breathing zone of the nose-only exposure chamber, the aerosol droplet size distribution was within the respirable diameter range. Rats were exposed to nicotine aerosol for 2 min. The arterial blood nicotine concentration reached 43.2 ± 15.7 ng/ml (mean ± SD) within 1-4 min and declined over the next 20 min, closely resembling the magnitude and early pharmacokinetics of a human smoking a cigarette. The acute inhalation toxicity of nicotine: LC50 = 2.3mg/L was determined; it was affected by pH, suggesting that acidification decreases nicotine absorption and/or bioavailability. A noninvasive method and toolkit were developed for delivering nicotine to rodents that enable rapid delivery of a controllable amount of nicotine into the systemic circulation and brain-inducing dose-dependent pharmacological effects, even a lethal dose. Aerosol inhalation can produce nicotine kinetics in both arterial and venous blood resembling human smoking. This method can be applied to studies of the effects of chronic intermittent nicotine exposure, nicotine addiction, toxicology, tobacco-related diseases, teratogenicity, and for discovery of pharmacological therapeutics.