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At least 901 records · Page 50Linked to original sources
PubMed2003

Percent free base nicotine in the tobacco smoke particulate matter of selected commercial and reference cigarettes.

The available evidence suggests that most of the nicotine in mainstream tobacco smoke is in the smoke particle matter (PM) phase. Nicotine can exist in protonated and free base forms in the smoke PM, and alpha(fb) is the fraction of the PM nicotine that is in the free base form. Because only the free base form can volatilize from the smoke PM phase to the gas phase of an inhaled aerosol and because gaseous nicotine deposits rapidly in the respiratory tract (RT), the magnitude and rate of nicotine deposition in the RT will depend on alpha(fb). The types of values that alpha(fb) can assume in the PM of cigarette smoke aerosols have not been well-known. The conventional view has been that mainstream cigarette smoke PM contains relatively little free base nicotine so that the cigarette smoker must absorb nicotine mostly from deposited particles. A prior study concluded that because cigarette smoke is at "pH 5.3", there is very little free base nicotine in such smoke. A 1994 internal tobacco company document discusses the view that "smoke pH" values for cigarette smoke are "approximately 6.0". This work uses volatility-based measurements to provide determinations of equilibrium nicotine alpha(fb) values for mainstream smoke PM from selected cigarettes. The effective pH (i.e., pH(eff)) of the smoke PM from selected brands of commercial cigarettes was found to span a range of 6.0-7.8 (nicotine alpha(fb) = 0.01-0.36), with all pH(eff) values much larger than 5.3 and most larger than 6.0.

Nicotine↗
PubMedDate not supplied

Estimation of particulate matter from visibility in Bangkok, Thailand.

Lack of daily data on airborne particles has been a common problem in an air pollution research. To deal with this problem, a regression model was developed to estimate daily PM10 concentration using visibility in Bangkok from 1992 to 1997, based on 1092 visibility/PM10 pair-observations on low humidity days (humidity < or = 76.5%). Visibility was significantly and inversely associated with PM10 (r = 0.71), after adjusting for minimum temperature and winter indicator variable. The R2 of the model was 0.51.

Air Movements↗
PubMed2003

Description and demonstration of the EXPOLIS simulation model: two examples of modeling population exposure to particulate matter.

As a part of the EXPOLIS study, a stochastic exposure-modeling framework was developed. The framework is useful to compare exposure distributions of different (sub-) populations or different scenarios, and to gain insight into population exposure distributions and exposure determinants. It was implemented in an MS-Excel workbook using @Risk add-on software. Basic concept of the framework is that time-weighted average exposure is a sum of partial exposures in the visited microenvironments. Partial exposure is determined by the concentration and the time spent in the microenvironment. In the absence of data, indoor concentrations are derived as a function of ambient concentrations, effective penetration rates and contribution of indoor sources. Framework input parameters are described by probability distributions. A lognormal distribution is assumed for the microenvironment concentrations and for the contribution of indoor sources, and a beta distribution for the time spent in a microenvironment and for the penetration factor. Mean and standard deviation values parameterize the distributions. In this paper, Latin Hypercube sampling is used for the input distributions. The outcome of the framework is an estimate of the population exposure distribution for the selected air pollutant. The framework is best suited for averaging times from 24 h upwards. Sensitivity analyses can be performed to determine the most influential factors of exposure. The application of the framework is illustrated in two examples. The EXPOLIS PM(2.5) example uses microenvironment measurement and time-activity data from the EXPOLIS study to model PM(2.5) population exposure distributions in four European cities. The results are compared to the observed personal exposure distributions from the same study. The Dutch PM(10) example uses input data from several (Dutch) databases and from literature, and shows a more complex application of the framework for comparison of scenarios and subpopulations.

Air Pollutants↗
PubMed2003

Influence of traffic patterns on particulate matter and polycyclic aromatic hydrocarbon concentrations in Roxbury, Massachusetts.

Vehicle emissions have been associated with adverse health effects in multiple epidemiological studies, but the sources or constituents responsible have not been established. Characterization of vehicle-related exposures requires detailed information on spatial and temporal trends of various pollutants and the ability to predict exposures in unmonitored settings. To address these issues, in the summer of 2001 we measured continuously particle-bound polycyclic aromatic hydrocarbons (PAHs), ultrafine particles, and PM(2.5) at a number of sites in Roxbury, a neighborhood of Boston, Massachusetts with significant diesel and gasoline-fueled traffic. We took measurements at the side of the road and at varying distances from the road, with simultaneous collection of traffic counts and meteorological conditions. Across all nine sites, median roadside concentrations were 8 ng/m(3) of particle-bound PAHs (range: 4-57), 16,000 ultrafine particles/cm(3) (range: 11,000-53,000), and 54 microg/m(3) of PM(2.5) as measured with a DustTrak (range: 12-86). Concentrations of all pollutants were lower at greater distances from the road, upwind, and at higher wind speeds, with greater concentration gradients for PAHs and ultrafine particles. In linear mixed effects regression models accounting for temporal autocorrelation, large diesel vehicle counts were significantly associated with roadside concentrations of PAHs (P=0.02), with a moderate association with ultrafine particles and little relation with PM(2.5). Although more comprehensive information would be needed for epidemiological applications, these data demonstrate significant spatial and temporal heterogeneity for traffic-related pollutants during the summer in an urban center, with our monitoring and analytical methodology helping to inform source attribution.

Air Pollutants↗
PubMed2006

Associations between personal exposures and fixed-site ambient measurements of fine particulate matter, nitrogen dioxide, and carbon monoxide in Toronto, Canada.

A longitudinal study investigating personal exposures to PM(2.5), nitrogen dioxide (NO(2)), and carbon monoxide (CO) for cardiac compromised individuals was conducted in Toronto, Canada. The aim of the study was (1) to examine the distribution of exposures to PM(2.5), NO(2), and CO; and (2) to investigate the relationship between personal exposures and fixed-site ambient measurements of PM(2.5), NO(2), and CO. In total, 28 subjects with coronary artery disease wore the Rupprecht & Patashnick ChemPass Personal Sampling System one day a week for a maximum of 10 weeks. The mean (SD) personal exposures were 22 microg m(-3) (42), 14 p.p.b. (6), and 1.4 p.p.m (0.5) for PM(2.5), NO(2), and CO, respectively. PM(2.5) and CO personal exposures were greater than central fixed-site ambient measurements, while the reverse pattern was observed for NO(2). Ambient PM(2.5) and NO(2) were correlated with personal exposures to PM(2.5) and NO(2) with median Spearman's correlation coefficients of 0.69 and 0.57, respectively. The correlations between personal exposures and ambient measurements made closest to the subjects' homes or the average of all stations within the study were not stronger than the correlation between personal exposures and central fixed-site measurements. Personal exposures to PM(2.5) were correlated with personal exposures to NO(2) (median Spearman's correlation coefficient of 0.43). This study suggests that central fixed-site measurements of PM(2.5) and NO(2) may be treated as surrogates for personal exposures to PM(2.5) and NO(2) in epidemiological studies, and that NO(2) is a potential confounder of PM(2.5).

Aged↗
PubMed2005

[Air quality and particulate matter].

Clean air is considered to be a key factor influencing human health. It is not only important for respiratory health but influences the homeostasis of the whole human organism. In this respect, all major national and international respiratory societies point to the extremely important role of national and international clean air acts that address both inner (i. e. tobacco smoke) and outer (i. e. environmental pollutants) air pollution. Due to research at the levels of pulmonary medicine and environmental medicine, the European Union has implemented new limit values. Clinical and experimental evidence points out that it is crucial to comply with these regulations since recent studies have shown that not only patients with lung diseases but also children and their lung development are endangered by high concentrations of air pollutants. With regard to the complexity of detrimental effects new national and international research programs should be established for the assessment of health effects of air pollutants.

Air↗
PubMed2003

Effects of uncontrolled particulate matter release on precipitation under warfare conditions.

This study has shown theoretical, observed and experimental evidence of pollutants released, transported and deposited during the Kosovo conflict in 1999 and their effects on precipitation in Serbia. The greatest bombardment of the chemical industry, oil refineries and fuel storage in Serbia which occurred during April, resulted in releases of many hazardous, toxic and cancerogenic substances. The number of April's days with precipitation greater or equal to 0.1 mm in 1999 are compared to those in the period from 1961 to 1990 registered at thirty meteorological stations in Serbia and especially at the Belgrade-Observatory station in the period from 1888 to 1995. The maximums of days with precipitation greater or equal to 0.1 mm were at the wider Belgrade area and at the central and southwestern parts of Serbia during April 1999. This is confirmed by using the Eta trajectory analysis.

Aerosols↗
PubMed1989

Relations between passage rates of rumen fluid and particulate matter and foam production in rumen contents of cattle fed on different diets ad lib.

1. A group of six cattle, three of which had a non-bloating history (group A) and had been ruminally cannulated for the previous 2 years, and three with a history of being bloat-prone (group B) and which had been ruminally cannulated only 3 months before the study, were fed ad lib. on chopped lucerne (Medicago sativa) hay, lucerne pellets, or a 100 g chopped hay and 900 g rolled barley grain/kg diet over three periods of 30 d each. Flow of rumen digesta, by reference to CoEDTA and chromium-mordanted fibres, and foam production from samples of rumen contents were measured. 2. Samples of rumen contents (50 ml) from group A produced foam heights of 150 and 60 mm, 2 and 4 h after feeding respectively, compared with 240 and 150 mm for group B (P less than 0.05). 3. The fractional passage rate of the 1-2 mm particles mordanted with Cr did not differ (P greater than 0.05) between groups. 4. The fractional outflow rates (FOR) for CoEDTA 0-2 h and 2-7 h after feed was offered were 0.205 and 0.160/h for group A and 0.093 and 0.086/h for group B respectively (P less than 0.05). 5. Rumen-fluid FOR 0-2 h and 2-7 h after provision of feed were significantly (P less than 0.05) inversely correlated (r -0.74 and -0.85 respectively) with the amount of foam produced from rumen contents at these times.

Animal Feed↗