Showing papers on "Smoke published in 2006"

Heat release of polymer composites in fire

Abstract: The relationship between heat release rate and other fire reaction properties of fibre reinforced polymer composite materials is investigated. The heat release rate and fire reaction properties of thermoset matrix composites reinforced with combustible fibres (aramid, extended-chain polyethylene) or non-combustible fibres (glass, carbon) were determined over a range of heat flux levels using the oxygen consumption cone calorimeter technique. The fire reaction properties that were measured were time-to-ignition, smoke density, carbon monoxide yield, carbon dioxide yield, mass loss rate and total mass loss. It is discovered that these reaction properties (apart from ignition time) are linearly related to the heat release rate for composites containing non-combustible fibres. When the reinforcement is combustible, however, the heat release rate only appears to be related to the carbon monoxide yield, mass loss rate and (in some cases) smoke density. This study clearly shows the importance of the relationship between heat release rate with smoke density and carbon monoxide yield, the two reaction properties that influence the survival of humans in fire.

Carcinogenicity of household solid fuel combustion and of high-temperature frying

Abstract: In October, 2006, 19 scientists from eight countries met at the International Agency for Research on Cancer (IARC) in Lyon, France, to assess the carcinogenicity of household solid fuel combustion (coal and biomass) and of high-temperature frying. These assessments will be published as volume 95 of the IARC Monographs. About half of the world’s population, mostly in low-resource and mediumresource coun tries, use solid fuels for cooking or heating, often in poorly ventilated spaces. WHO identifi ed in door smoke from combustion of solid fuels as one of the top ten risks for worldwide burden of disease. Products of incomplete combustion contain respirable (coarse, fi ne, and ultrafi ne) particles and many volatile and nonvolatile organic compounds, including carcinogens such as benzo[a]pyrene, formaldehyde, and benzene. Average indoor concen trations of particulate matter (<10 μm) can be as high as several milligrams per cubic metre, with peak concentrations an order of magnitude higher. Women and young children who are at home for most of the day are most highly exposed. Although occupational exposure to the combustion products of coal by inhalation is known to cause lung cancer, many studies, mostly from China, now show similar eff ects from household use of coal. The problem was fi rst noted in the county of Xuan Wei, China, where the type of coal used produces especially smoky emissions. Two case–control studies from Xuan Wei reported a positive exposure– response relationship between the amount of coal used and the risk of lung cancer. Subsequently, a cohort intervention study showed transition to the use of a stove with a chimney from one without reduced this risk. A large study in Shenyang, China, noted positive exposure–response associations for diff erent measures of exposure to coal smoke—including a cumulative index of indoor exposure— after adjust ing for smoking and education. Furthermore, a study of non-smoking women in Harbin, China, reported a strong exposure–response relationship between years of use of a coal stove and lung cancer. Case– control studies from Taiwan and the USA have also reported a twofoldincreased risk for lung cancer as a result of coal-smoke inhalation after adjusting for potential confounders. In experiments with animals, inhalation of emissions from coal, burned under conditions similar to those in Xuan Wei, increased the incidence of various types of malignant lung tumours in male and female Kunming mice and of squamous-cell carcinomas in male and female Wistar rats. In another study, the incidence of adenocarcinoma of the lung was increased in male and female Kunming mice exposed to combustion emissions of coal obtained from Harbin. On the basis of suffi cient evidence in both humans and experimental animals, the Working Group concluded that indoor emissions from household combustion of coal are “carcinogenic to humans (Group 1)”. Mechanistic data from studies of humans and animals are consistent with this conclusion. Biomass fuel is much more widely used than coal but the adverse health eff ects have been studied less. In Taiwan, women who burned wood for cooking had a threefold increase in the risk of lung cancer after adjusting for potential confounders. Additionally, a large multicentre European case– control study recorded an adjusted 20–30% increased risk of lung cancer in people who burned wood but not coal, compared with people who never used coal or wood for cooking or heating. Studies in Japan and Mexico also found an increased risk of lung cancer in non-smoking women, which was related to their exposure to smoke from wood or straw. These studies suggest that exposure to smoke from wood combustion is associated with an increased risk of lung cancer; however, the results on exposure duration and intensity are diffi cult to interpret. In animal experiments, exposure to emissions from wood, burned under conditions similar to those in Xuan Wei, increased the incidence of lung adenocarcinomas in male and female Kunming mice, but not in Wistar rats. Extracts from wood smoke, applied to the skin or given subcutaneously, produced cancer in mice and rats. Combustion emissions from wood are mutagenic because of the presence of compounds from various chemical classes, including polycyclic aromatic hydrocarbons and acidic or polar substances. Molecular data, which include changes in expression and phosphorylation of P53 in patients with lung cancer who were exposed to wood smoke, and systemic genotoxicity in charcoal workers and in women who burn cow dung or wood, supports evidence of carcinogenicity of emissions from burning wood. On the basis of limited evidence of carcinogenicity of biomass combustion emissions (mainly from wood) in humans and experimental animals; suffi cient evidence of carcino genicity of wood-smoke extracts in experimental animals; and strong evidence of mutagenicity, Upcoming meetings

Mesoscale modeling of Central American smoke transport to the United States: 1. “Top-down” assessment of emission strength and diurnal variation impacts

Abstract: [1] As is typical in the Northern Hemisphere spring, during 20 April to 21 May 2003, significant biomass burning smoke from Central America was transported to the southeastern United States (SEUS). A coupled aerosol, radiation, and meteorology model that is built upon the heritage of the Regional Atmospheric Modeling System (RAMS), having newly developed capabilities of Assimilation and Radiation Online Modeling of Aerosols (AROMA) algorithm, was used to simulate the smoke transport and quantify the smoke radiative impacts on surface energetics, boundary layer, and other atmospheric processes. This paper, the first of a two-part series, describes the model and examines the ability of RAMS-AROMA to simulate the smoke transport. Because biomass-burning fire activities have distinct diurnal variations, the FLAMBE hourly smoke emission inventory that is derived from the geostationary satellite (GOES) fire products was assimilated into the model. In the “top-down” analysis, ground-based observations were used to evaluate the model performance, and the comparisons with model-simulated results were used to estimate emission uncertainties. Qualitatively, a 30-day simulation of smoke spatial distribution as well as the timing and location of the smoke fronts are consistent with those identified from the PM2.5 observation network, local air quality reports, and the measurements of aerosol optical thickness (AOT) and aerosol vertical profiles from the Southern Great Plains (SGP) Atmospheric Radiation Measurements (ARM) site in Oklahoma. Quantitatively, the model-simulated daily mean near-surface dry smoke mass correlates well with PM2.5 mass at 34 locations in Texas and with the total carbon mass and nonsoil potassium mass (KNON) at three IMPROVE sites along the smoke pathway (with linear correlation coefficients R = 0.77, 0.74, and 0.69 at the significance level larger than 0.99, respectively). The top-down sensitivity analysis indicates that the total smoke particle emission during the study period is about 1.3 ± 0.2 Tg. The results further indicate that the simulation with a daily smoke emission inventory provides a slightly better correlation with measurements in the downwind region on daily scales but gives an unrealistic diurnal variation of AOT in the smoke source region. This study suggests that the assimilation of emission inventories from geostationary satellites is superior to that of polar orbiting satellites and has important implications for the modeling of air quality in areas influenced by fire-related pollutants from distant sources.

The retention of tobacco smoke constituents in the human respiratory tract.

Abstract: Measurements on the retention of cigarette smoke constituents in the human respiratory tract have been undertake for more than 100 years. The first studies on nicotine retention were begun by Lehmann in Germany in 1903 and published in 1908. The first studies on the retention of smoke particulate matter were published by Baumbereger in the United States in 1923. Since those early publications, many studies have been undertaken, more or less continuously. This article is a review of the work that has been done over the last 100 years, including a large number of unpublished studies undertaken by British American Tobacco in Southampton, UK. The techniques used have evolved over the years and there is a certain amount of variation in the data. However, the general trends in the results are reassuringly consistent. The bulk of the studies indicate that, on average, 60 to 80% of the mainstream smoke particulate matter is retained in the lungs after inhalation. For nicotine, carbon monoxide, nitric oxide, and aldehydes the total retentions are of the order of 90-100, 55-65, 100, and approximately 90%, respectively, during cigarette smoke inhalation. For most smoke constituents the retentions in the mouth only are considerably smaller than in the whole respiratory tract. The lung retention values for smoke particulate matter are dependent on the depth of inhalation, hold time in the lungs, exhalation volume, and other factors. However, the degree of nicotine retention following inhalation is not markedly influenced by changes in respiratory parameters. Furthermore, the percentage retentions for smoke particulate matter and nicotine are smaller for nonsmoking subjects exposed to environmental tobacco smoke than with active smoking. The smoke retentions are related to properties of the smoke aerosol particles and gases and their behavior as they travel through the respiratory tract. This includes particle growth in the respiratory tract and evaporation of gases out of the particles, and relevant aspects of these processes are also reviewed.

Modeling of biomass smoke injection into the lower stratosphere by a large forest fire (Part II): sensitivity studies

Abstract: The Chisholm forest fire that burned in Alberta, Canada, in May 2001 resulted in injection of substantial amounts of smoke into the lower stratosphere. We used the cloud-resolving plume model ATHAM (Active Tracer High resolution Atmospheric Model) to investigate the importance of different contributing factors to the severe intensification of the convection induced by the Chisholm fire and the subsequent injection of biomass smoke into the lower stratosphere. The simulations show strong sensitivity of the pyro-convection to background meteorology. This explains the observed coincidence of the convective blow-up of the fire plume and the passage of a synoptic cold front. Furthermore, we performed model sensitivity studies to the rate of release of sensible heat and water vapor from the fire. The release of sensible heat by the fire plays a dominant role for the dynamic development of the pyro-cumulonimbus cloud (pyroCb) and the height to which smoke is transported. The convection is very sensitive to the heat flux from the fire. The emissions of water vapor play a less significant role for the injection height but enhance the amount of smoke transported beyond the tropopause level. The aerosol burden in the plume has a strong impact on the microphysical structure of the resulting convective cloud. The dynamic evolution of the pyroCb, however, is only weakly sensitive to the abundance of cloud condensation nuclei (CCN) from the fire. In contrast to previous findings by other studies of convective clouds, we found that fire CCN have a negative effect on the convection dynamics because they give rise to a delay in the freezing of cloud droplets. Even in a simulation without fire CCN, there is no precipitation formation within the updraft region of the pyroCb. Enhancement of convection by aerosols as reported from studies of other cases of convection is therefore not found in our study.

Indonesian peat and vegetation fire emissions: Study on factors influencing large-scale smoke haze pollution using a regional atmospheric chemistry model

Abstract: Numerical modelling of fire-related smoke haze episodes in Southeast Asia is important for both prediction and assessment of atmospheric impacts, especially when observational data are fragmentary, as is the case in Indonesia. This work describes the atmospheric fate of smoke particles emitted during the 1997 Indonesian fires modelled with a regional atmospheric chemistry model. We established a new fire emission inventory and calculate that 55 teragram (Tg) of particulate matter and 1098 Tg of carbon were released during this fire episode. Our emission estimate is an intermediate value compared with other studies. Utilising different scenarios, we demonstrate the variable atmospheric impacts of surface vegetation fires and peat soil fires separately and also investigate the sensitivity of smoke dispersion to the differing meteorological conditions of an El Nino and a normal year. When peat fires are included in the emission inventory, modelled ambient particle concentrations exceed the ambient air quality standard across transboundary scales. In a scenario including only surface vegetation fires, ambient air quality standards are exceeded only in areas close to the main fires. This scenario demonstrates the prominent role of fires in peat areas in causing regional air pollution episodes. In years with normal meteorological conditions, intermittent precipitation and associated wet deposition during the dry season are predicted to remove most of the particulate emissions close to the sources. Strongly reduced rainfall and generally stronger southeasterly winds during El Nino years provide favourable conditions for larger scale smoke haze pollution.

An Analysis of Effects of San Diego Wildfire on Ambient Air Quality

Abstract: The impact of major gaseous and particulate pollutants emitted by the wildfire of October 2003 on ambient air quality and health of San Diego residents before, during, and after the fire are analyzed using data available from the San Diego County Air Pollution Control District and California Air Resources Board. It was found that fine particulate matter (PM) levels exceeded the federal daily 24-hr average standard during the fire. There was a slight increase in some of the gaseous pollutants, such as carbon monoxide, which exceeded federal standards. Ozone (O3) precursors, such as total hydrocarbons and methane gases, experienced elevated concentration during the fire. Fortunately, the absence of sunlight because of the cloud of thick smoke that covered most of the county during the fire appears to have prevented the photochemical conversion of the precursor gases to harmful concentrations of O3. Statistical analysis of the compiled medical surveillance data has been used to establish correlation...

High Levels of Dioxin-Like Potential in Cigarette Smoke Evidenced by In vitro and In vivo Biosensing

Abstract: Cigarette smoke contains low levels of agonists for the aryl hydrocarbon receptor (AhR; also called the dioxin receptor). However, little is understood about the whole potential of cigarette smoke for activating AhR. In this report, we evaluated the total "dioxin-like" activity of cigarette smoke using in vitro and in vivo reporter systems. Cigarette smoke extract (CSE) was prepared from seven cigarette brands (1-20 mg tar content) and subjected to in vitro bioassay based on the xenobiotic-responsive element (XRE) as the sensor and secreted alkaline phosphatase (SEAP) as the reporter. Exposure of reporter cells to CSE triggered activation of XRE in a dose-dependent manner, which was suppressed by functional inhibition of AhR. Direct, brief exposure of the cells to cigarette smoke similarly induced activation of XRE. Using 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) as the standard, the XRE-activating potential (XAP) of individual smoke was evaluated quantitatively. Positive correlation was observed between the tar content and XAP values. The XAP values estimated were extremely high with a range from 18.5 to 51.2 ng 2,3,7,8-TCDD equivalent per cigarette. To further estimate XAP of cigarette smoke in vivo, we generated transgenic reporter mice that secrete SEAP under the control of XRE. After exposure of the mice to smoke, serum levels of SEAP were significantly elevated within 12 hours, peaked at 24 hours, and declined thereafter. These results evidenced for the first time that cigarette smoke has unexpectedly high dioxin-like potential that triggers the AhR-XRE pathway in vitro and in vivo.

Mesoscale modeling of Central American smoke transport to the United States: 2. Smoke radiative impact on regional surface energy budget and boundary layer evolution

Abstract: [1] During 20 April to 21 May 2003, large amounts of smoke aerosols from Central American Biomass Burning (CABB) fires were transported to southeastern United States. Using a coupled aerosol, radiation, and meteorology model built upon the heritage of the Regional Atmospheric Modeling System (RAMS) with new capabilities called the Assimilation and Radiation Online Modeling of Aerosols (AROMA), this paper, the second of a two-part series, investigates smoke radiative impact on the regional surface energy budget, temperature and relevant boundary layer processes. Comparisons with limited ground-based observations and MODIS aerosol optical thickness (AOT) showed that model consistently simulated the smoke AOT and smoke radiative impacts on the 2 m air temperature (2mT) and downward shortwave irradiance (DSWI). Over 30 days the 24-hour mean smoke AOT was 0.18 (at 0.55 μm) near the smoke source region (Yucatan Peninsula and southern Mexico), and 0.09 in downwind region (e.g., southern Texas), both showing a diurnal variation of 24%. Maximum AOT occurred during late afternoon and minimum during early morning in smoke source region. The smoke radiative effects were dominant mostly during the daytime and resulted in the decrease of DSWI, sensible heat and latent heat by 22.5 Wm−2, 6.2 Wm−2, and 6.2 Wm−2, respectively, near the source region, in contrast to 15.8 Wm−2, 4.7 Wm−2, and 7.9 Wm−2, respectively, in downwind regions. Both maximum and minimum 2mT were decreased, and the overall diurnal temperature range (DTR) was reduced by 0.31°C and 0.26°C in the smoke source and downwind regions, respectively. The smoke absorption of solar radiation increased the lapse rate by 0.1–0.5 K/day in the planetary boundary layer (PBL), thus warming the air over the ocean surface. However, over the land surface where the coupling between the lower PBL and the cooler land surface is strong, such warming only occurred in the upper PBL and is amendable to the diurnal variation of smoke emission. The simulation numerically verifies the smoke self-trapping feedback mechanism proposed by Robock (1988), where the increase of the atmospheric stability in the PBL caused by the smoke radiative effects further traps more smoke aerosols in the lower PBL. Such feedbacks, when coupled with favorable synoptic systems, may have important implications for air quality modeling and hydrological processes.

Arctic smoke record high air pollution levels in the European Arctic due to agricultural fires in Eastern Europe

Abstract: In spring 2006, the European Arctic was abnormally warm, setting new historical temperature records. During this warm period, smoke from agricultural fires in Eastern Europe intruded into the European Arctic and caused the most severe air pollution episodes ever recorded there. This paper confirms that biomass burning (BB) was indeed the source of the observed air pollution, studies the transport of the smoke into the Arctic, and presents an overview of the observations taken during the episode. Fire detections from the MODIS instruments aboard the Aqua and Terra satellites were used to estimate the BB emissions. The FLEXPART particle dispersion model was used to show that the smoke was transported to Spitsbergen and Iceland, which was confirmed by MODIS retrievals of the aerosol optical depth (AOD) and AIRS retrievals of carbon monoxide (CO) total columns. Concentrations of halocarbons, carbon dioxide and CO, as well as levoglucosan and potassium, measured at Zeppelin mountain near Ny Alesund, were used to further corroborate the BB source of the smoke at Spitsbergen. The ozone (O 3 ) and CO concentrations were the highest ever observed at the Zeppelin station, and gaseous elemental mercury was also enhanced. A new O 3 record was also set at a station on Iceland. The smoke was strongly absorbing ? black carbon concentrations were the highest ever recorded at Zeppelin ?, and strongly perturbed the radiation transmission in the atmosphere: aerosol optical depths were the highest ever measured at Ny Alesund. We furthermore discuss the aerosol chemical composition, obtained from filter samples, as well as the aerosol size distribution during the smoke event. Photographs show that the snow at a glacier on Spitsbergen became discolored during the episode and, thus, the snow albedo was reduced. Samples of this polluted snow contained strongly enhanced levels of potassium, sulphate, nitrate and ammonium ions, thus relating the discoloration to the deposition of the smoke aerosols. This paper shows that, to date, BB has been underestimated as a source of aerosol and air pollution for the Arctic, relative to emissions from fossil fuel combustion. Given its significant impact on air quality over large spatial scales and on radiative processes, the practice of agricultural waste burning should be banned in the future.

Variability of fire behavior, fire effects, and emissions in scotch pine forests of central siberia

Abstract: As part of the Russian FIRE BEAR (Fire Effects in the Boreal Eurasia Region) Project, replicated 4-ha experimental fires were conducted on a dry Scotch pine (Pinus sylvestris)/lichen (Cladonia sp.)/feathermoss (Pleurozeum schreberi) forest site in central Siberia. Observations from the initial seven surface fires (2000-2001) ignited under a range of burning conditions quantified the different fuel consumption and fire behavior characteristics (e.g., rate of spread, fireline intensity, etc.) possible in this particular forest fuel type. Experimental results and dendrochronological study of local fire history both support the dominance of local fire regimes by low to moderate-intensity surface fires. Carbon released by the experimental fires ranged from 4.8 to 15.4 t C ha− 1 depending on fuel conditions and fire severity. Preliminary emission data show a strong correlation between carbon dioxide (CO2) and carbon monoxide (CO) emissions, which should facilitate accurate estimates of fire impacts on atmospheric chemistry. Carbon concentration in smoke samples was related to fire severity. The short landscape-scale fire-return interval (50 years), combined with typically low fire severity, in pine ecosystems of central Siberia is often associated with low tree mortality and relatively rapid buildup of litter and understory fuels after a fire.

Aerosol Smoke and Smoke‐Water Stimulation of Seedling Vigor of a Commercial Maize Cultivar

Abstract: The effect of smoke as a germination cue is well documented. Recent developments in smoke technology have suggested that smoke also improves vigor. It has been reported that indigenous storage methods of South African maize landraces using smoke enhances seedling vigor. This present study highlights the effects of aerosol smoke and smoke-water on the germination and seedling vigor of a commercial maize cultivar, Zea mays L. var. PAN 6479. Various presoaking and smoking combinations were investigated. Treating seeds with aerosol smoke showed significant (p < 0.05) stimulatory effects on vigor. However, prolonged exposure to aerosol smoke resulted in reduced germination which was alleviated by rinsing the seeds. Furthermore, presoaking seeds before exposure to aerosol smoke also significantly (p < 0.05) reduced the inhibitory effect of prolonged smoking. The combination of presoaking and smoking had a significant (p < 0.05) improvement on the percentage germination. This study also showed that smoke has the potential to improve not only the percentage germination but also seedling vigor of commercially bred maize seeds.

Particle emissions from laboratory combustion of wildland fuels: In situ optical and mass measurements

Abstract: [1] Time-resolved optical properties of smoke particles from the controlled laboratory combustion of mid-latitude wildland fuels were determined for the first time using advanced techniques, including cavity ring-down/cavity enhanced detection (CRD/CED) for light extinction and two-wavelength photoacoustic detection for light absorption. This experiment clearly resolves the dependence of smoke properties on fuel and combustion phase. Intensive flaming combustion during ponderosa pine wood (PPW) burning produces particles with a low single scattering albedo of 0.32 and a specific mass extinction efficiency of 8.9 m2 g−1. Burning white pine needles (WPN) features a prolonged smoldering phase emitting particles that are not light-absorbing and appear much larger in size with an extinction efficiency ≈5 m2 g−1. A Mie scattering model was formulated, which estimates the black carbon fraction in the PPW and WPN smoke particles at 66% and 12%, respectively. These observations may refine the current radiative forcing estimates for biomass burning emissions.

Quantitative puff-by-puff-resolved characterization of selected toxic compounds in cigarette mainstream smoke.

Abstract: Soft single photon ionization (SPI)−time-of-flight mass spectrometry (TOFMS) has been applied for the quantitative puff-by-puff-resolved characterization of selected toxic species in cigarette mainstream smoke, namely, nitric oxide (NO), acetaldehyde, butadiene, acetone, isoprene, benzene, toluene, ethyl benzene, and xylene. The 2R4F research cigarette was investigated for whole smoke (unfiltered) and gas phase (filtered). It has been demonstrated that the existing smoking regime for total smoke analysis (smoke from a complete cigarette) features deficiencies when applied to puff-resolved measurements. This is especially the case for analysis in which a glass fiber filter is used to separate the smoke particulate and gas phases because material is desorbed from the filter and influences succeeding puffs. Regarding whole smoke measurements, succeeding puffs are affected by contamination and memory effects of the smoking machine itself, but to a lower extent. Quantitative puff-resolved smoke profiles show t...

Brand differences of free-base nicotine delivery in cigarette smoke: the view of the tobacco industry documents.

Abstract: The recent availability of internal tobacco industry documents provides significant insight into industry knowledge and manipulation of tobacco smoke delivery. One critical area of research is the role of smoke chemistry in determining the absorption and effects of smoke constituents, especially harm producing or pharmacologically active compounds. Independent scientific research has suggested that the nicotine dosing characteristics, hence the addiction potential of cigarettes, may be determined in part by the amount of free-base nicotine in cigarette smoke and its effects on the location, route, and speed of absorption in the body and on the sensory perception effects of the inhaled smoke. Tobacco industry documents describe the use of a number of methods internally for measuring free-base nicotine delivery. These include the common use of cigarette "smoke pH" as a means to estimate the fraction of free-base nicotine in the particulate matter (PM) in cigarette smoke, as well as efforts to measure free-base nicotine directly. Although these methods do not provide accurate absolute measures of free-base nicotine in smoke, consistencies observed in the findings across the various manufacturers indicate: (1) real relative differences in the acid/base chemistry of the smoke from different brands of cigarettes; (2) a connection between differences in free-base levels and brand-dependent differences in sensory perception and smoke "impact"; and (3) levels of free-base nicotine that are greater than have typically been publicly discussed by the industry. Furthermore, the results of these methods are generally consistent with those of a recent study from the Centers for Disease Control and Prevention which directly measured the free-base fraction of nicotine across a range of cigarette types. Consideration of the likely fundamental importance of free-base nicotine levels in cigarette smoke, together with the efforts discussed in the tobacco industry documents to measure such levels, indicates that the public health community would benefit from additional research to assess directly the delivery of free-base nicotine in cigarette smoke across brands. This may be especially useful for those products ("light", "ultralight", "reduced carcinogen", etc) that have been promoted, either explicitly or implicitly, as "harm reducing".

Humidification factors from laboratory studies of fresh smoke from biomass fuels

Abstract: [1] Measurements of smoke aerosol humidification factors were performed in a laboratory for different biomass fuel types and burn conditions. Two nephelometers simultaneously measured dry and humidified light scattering coefficients (bsp(dry) and bsp(RH), respectively), providing the first observations of the temporal evolution of the humidification factor (f(RH) = bsp(RH)/bsp(dry)) for fresh (minutes-old) smoke. Hygroscopic characteristics of the smoke aerosols varied with fuel type and fire conditions, with the mean f(RH) ranging from 1.01 to 1.95 for fresh minutes-old smoke for the relative humidity (RH) range of 70–94%. These f(RH) values exhibited temporal variability, with some fuels alternating from hygroscopic to nonhygroscopic within minutes. Humidograms were also obtained, demonstrating that smoke from different fuels begins to take up water at different RH values. Humidification factors for hour-old smoke ranged from 1.10 to 1.51 for RH > 90%. Finally, light-absorbing carbon mass measured with a multiwavelength aethalometer demonstrated different spectral responses as a function of fuel type. These laboratory experiments demonstrate the complexity of smoke hygroscopicity from young fires and are essential for understanding the radiative effects of biomass burning in the ambient atmosphere.

Arsenic and Cigarette Smoke Synergistically Increase DNA Oxidation in the Lung

Abstract: Epidemiological evidence has indicated that arsenic and cigarette smoking exposure act synergistically to increase the incidence of lung cancer. Since oxidative damage of DNA has been linked to cancer, our hypothesis is that aerosolized arsenic and cigarette smoke work synergistically to increase oxidative stress and increase DNA oxidation in the lung. To test this hypothesis male Syrian golden hamsters were exposed to room air (control), aerosolized arsenic compounds (3.2 mg/m3 for 30 minutes), cigarette smoke (5 mg/m3 for 30 minutes), or both smoke and arsenic. Exposures were for 5 days/week for 5 or 28-days. Animals were sacrificed one day after the last exposure. In the 28-day group, glutathione levels and DNA oxidation (8-oxo-2'-deoxyguanosine (8-oxo-dG)) were determined. Our results show that in the 28-day arsenic/smoke group there was a significant decrease in both the reduced and total glutathione levels compared with arsenic or smoke alone. This correlated with a 5-fold increase in DNA oxidation as shown by HPLC. Immunohistochemical localization of 8-oxo-dG showed increase staining in nuclei of airway epithelium and subadjacent interstitial cells. These results show that dual exposure of arsenic and cigarette smoke at environmentally relevant levels can act synergistically to cause DNA damage.