Modelling dust extinction in the Magellanic Clouds

We model the extinction profiles observed in the Small and Large Magellanic clouds with a synthetic population of dust grains consisting by core-mantle particles and a collection of free-flying polycyclic aromatic hydrocarbons. All different flavors of the extinction curves observed in the Magellanic Clouds can be described by the present model, that has been previously (successfully) applied to a large sample of diffuse and translucent lines of sight in the Milky Way. We find that in the Magellanic Clouds the extinction produced by classic grains is generally larger than absorption by polycyclic aromatic hydrocarbons. Within this model, the non-linear far-UV rise is accounted for by polycyclic aromatic hydrocarbons, whose presence in turn is always associated to a gap in the size distribution of classical particles. This hints either a physical connection between (e.g., a common cause for) polycyclic aromatic hydrocarbons and the absence of middle-sized dust particles, or the need for an additional component in the model, that can account for the non-linear far-UV rise without contributing to the UV bump at $\sim$217 nm, e.g., nanodiamonds

The Association of Urinary Polycyclic Aromatic Hydrocarbons Biomarkers and Markers of Inflammation, Diabetes Mellitus and Cardiovascular Disease

Polycyclic aromatic hydrocarbons are potent atmospheric pollutants, released into air during incomplete combustion of fuel, industrial or domestic coal, wood, cigarette smoke and other organic materials. In addition to being carcinogenic, several animal studies have reported positive associations between polycyclic aromatic hydrocarbons and inflammation, oxidative stress and the development and progression of atherosclerosis. Occupational studies have reported positive associations between polycyclic aromatic hydrocarbons and cardiovascular morbidity and mortality. Moreover, there is evidence that polycyclic aromatic hydrocarbons may cause disruption of the endocrine system. It is still not clear if lower background exposure to polycyclic aromatic hydrocarbons, independent of the adverse health effects of smoking, is associated with increased risk of inflammation, diabetes mellitus and cardiovascular disease in the general population. We examined participants from the merged National Health and Nutrition Examination Survey 2001-02, 2003-2004, and 2005-2006. Our exposures of interest were eight urinary monohydroxy polycyclic aromatic hydrocarbons and our outcomes were serum markers of systemic inflammation, including: serum C-reactive protein and total white blood cell count, diabetes mellitus and self-reported cardiovascular disease. Urinary biomarkers of the low molecular weight polycyclic aromatic hydrocarbons were found to be positively associated with serum C-reactive protein, total white blood cell count and diabetes mellitus independent of potential confounders. Levels of 1-hydroxypyrene, the urinary metabolite of the higher molecular weight PAH, pyrene, showed a less strong association with serum C-reactive protein and diabetes mellitus. The evidence on the association between polycyclic aromatic hydrocarbons and self-reported cardiovascular disease was limited, only 1-hydroxynapthalene, summed biomarkers of low molecular weight polycyclic aromatic hydrocarbons, and 1- hydroxypyrene showed statistically significant positive associations with cardiovascular disease independent of potential confounders. In conclusion, this study provides evidence on the positive association of background exposure to polycyclic aromatic hydrocarbons and serum C-reactive protein, total white blood cell count, diabetes mellitus and cardiovascular disease. Further prospective studies are needed to replicate or refute our findings

Polycyclic aromatic hydrocarbons (PAHs)

How to use this course -- Initial check -- What are polycyclic aromatic hydrocarbons (PAHs)? -- Where are polycyclic aromatic hydrocarbons (PAHs) found? -- What are the routes of exposure for polycyclic aromatic hydrocarbons (PAHs)? -- Who is at risk of exposure to polycyclic aromatic hydrocarbons (PAHs)? -- What are the standards and regulations for polycyclic aromatic hydrocarbons (PAH) exposure? -- What is the biologic fate of PAHs in the body? -- How do PAHs induce pathogenic change? -- What health effects are associated with PAH exposure? -- Clinical assessment -- How should patients exposed to PAHs be treated and managed? -- What instructions should be given to patients to prevent overexposure to PAHs? -- Sources of additional information -- Assessment and posttest -- Literature cited"Course: WB 1519.""CE original date: July 1, 2009.""CE Expiration date: July 1, 2012.""ATSDR Authors: Kim Gehle, MD, MPH."Includes bibliographical references (p. 59-68).200

Biodegradation of Petroleum Hydrocarbons in Contaminated Coastal Environments, Nigeria

ABSTRACT To compare the degree of biodegradation of petroleum hydrocarbons in sediments from Ikarama and Okwori in the Niger delta, Nigeria, concentrations of n-alkanes and polycyclic aromatic hydrocarbons in the sediments were measured. Analysis was conducted with gas chromatography using mass spectrometry detector. While the decrease in concentrations of n-alkanes and polycyclic aromatic hydrocarbons confirmed the process of biodegradation in the sediments it was not solely fit to substantiate the degree of biodegradation in the sediments. Hence the percentage proportion of n-alkanes and polycyclic aromatic hydrocarbons was used. The degree of biodegradation of n-alkanes in both Okwori and Ikarama was almost similar. However, it was observed that polycyclic aromatic hydrocarbons were biodegraded in Okwori sediments than Ikarama sediments and this indicates the degree of biodegradation of petroleum hydrocarbons impacted sediments in Okwori is greater than that of Ikarama

Bioremediation of PAHs-Contaminated Soil Using Land Treatment Processes

Polycyclic aromatic hydrocarbons (PAHs) are present in crude oil and its derivatives contaminate soil and also increase carcinogen and mutagen contamination, which is a concern for researchers. Land farming is one of the methods that remove pollutants from the soil by native microorganisms. It seems that this technology is cost-effective, environmentally friendly and causes less debris problem to be disposed. This study aimed to refine the polycyclic aromatic hydrocarbons from oil-contaminated soil using the land farming method. In addition to examine the concentration of polycyclic aromatic hydrocarbons by GC-FID, some characteristics such as soil microbial respiration and dehydrogenase, peroxidase, urease, acid and alkaline phosphatase enzyme concentration were also measured. The results showed that after land farming process the concentrations of some polycyclic aromatic hydrocarbons dropped to 50 percent. The results showed that the enzyme concentration is reduced by reducing the concentration of hydrocarbons and microbial respiration. These results emphasize the process of land farming for removal of polycyclic aromatic hydrocarbons from soil by indigenous microorganisms

Identification of polycyclic aromatic hydrocarbons

The nature of the Very Small Grains evidenced by K. Sellgren (1985) is discussed. Thsir stability suggests that they are graphitic material and specifically Polycyclic Aromatic Hydrocarbons (PAHs). The expected infrared emission of a typical PAH, coronene, gives an impressive spectroscopic agreement with the five observed Unidentified IR Emission Features, leading to an unambiguous identification. Those PAHs are the most abundant organic molecules detected to date (f is approximately .00001)

Polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons (PAH) are a group of structurally related chemical compounds that are frequently produced during incomplete combustion of organic matter and are among the most widespread environmental pollutants. This chapter enumerates common sources of environmental PAH that contribute to human exposures including air and water pollution, residential soil and marine sediments, occupational exposures, and lifestyle sources such as cigarette smoking and diet. It summarizes toxic effects in humans, particularly carcinogenesis, along with recent developments in measurable biomarkers of exposure