• Some have hydrogen with rings of carbon atoms, called polycyclic aromatic hydrocarbons or PAHs. (cdc.gov)
  • Researchers at Uppsala University and AstraZeneca utilized Baird's rule to show that benzene and several polycyclic aromatic hydrocarbons (PAHs) will undergo metal-free photochemical (hydro)silylations and transfer-hydrogenations at mild conditions, with the highest yield for naphthalene (photosilylation: 21 percent). (photonics.com)
  • Polycyclic aromatic hydrocarbons (PAHs) are chemicals that are released into the environment during activities of the petroleum industry. (researchgate.net)
  • Offshore drilling operations discharge large amounts of toxic wastes that contain mercury, benzene, arsenic, lead and Polycyclic aromatic hydrocarbons (PAHs). (rep.org)
  • This view is supported by research demonstrating that they contain toxic chemicals within their structure and also adsorb additional chemicals, including polychlorinated biphenyls (PCBs), pesticides, metals, and polycyclic aromatic hydrocarbons (PAHs), from the environment. (researchgate.net)
  • One generalization of the benzene ring structure that is of particular interest to the Ames Astrophysics and Astrochemistry laboratory are the polycyclic aromatic hydrocarbons, also referred to as PAHs (monocylic benzene being a sort of honorary PAH). (astrochem.org)
  • PAHs consist of multiple fused rings of carbon atoms (as in figure 2) with a benzene-like decoration of hydrogen atoms around their exterior perimeters. (astrochem.org)
  • Figure 2: the highly stylized planar structures of some simple, benzenoid PAHs Polycyclic aromatic hydrocarbons with a "decoration" that consists only of hydrogen atoms are commonly represented by simple hexagons. (astrochem.org)
  • Shown here are the aromatic skeletons of PAHs with two to four rings. (astrochem.org)
  • The net effect is that the chemistry of the hot gas mixture favors growth from small hydrocarbons to larger ones with PAHs commonly being one of the end products. (astrochem.org)
  • polycyclic aromatic hydrocarbons (PAHs) containing up to three or four carbon rings. (gizmodo.com)
  • The new research shows that PAHs, including naphthalene and phenanthrene and its precursors benzene, phenylacetylene, and styrene, can be synthesized by irradiating frozen acetylene-a process that might be happening on Titan's surface and subsequently acting as "as a critical molecular feedstock to the organic dune material," the authors wrote in the study. (gizmodo.com)
  • Diesel exhaust contains benzene, PAHs, toluene, and xylene, and workers who are frequently exposed to diesel fumes could be at higher risk of colon cancer than others. (doranandmurphy.com)
  • Much attention has been paid to the particular exposure of skin to polycyclic aromatic hydrocarbons (PAHs), despite protective gear and decontamination processes. (nphic.org)
  • The research team will use scientifically established approaches to understand the types of health problems community members are experiencing, and how these conditions may be linked to exposure to chemicals found in coke oven emissions, such as benzene and polycyclic aromatic hydrocarbons. (buffalo.edu)
  • Hydrocarbons are a class of chemicals that contain only hydrogen and carbon atoms. (cdc.gov)
  • When these are burned in the engine combustion process, they form new highly toxic chemicals including dioxin and a group of chemicals called polycyclic aromatic hydrocarbons (PAH for short). (chem-tox.com)
  • Car exhaust is a major source of the carcinogenic and neurotoxic chemicals polycyclic aromatic hydrocarbons (PAH). (chem-tox.com)
  • The burned charcoal releases chemicals such as carbon monoxide (CO), polyaromatic hydrocarbons (PAH) and other combustion-related toxins that the smoker inhales. (who.int)
  • He has also used environmental measurements and biomarkers to elucidate the human metabolism of several toxic chemicals, notably benzene, and to quantify interindividual variability in biomarker levels due to genetic, environmental and lifestyle factors. (berkeley.edu)
  • 2] In addition, production of asphalt releases hazardous chemicals such as polycyclic aromatic hydrocarbons, hydrogen sulfide, lead, and copper into the environment exposing fenceline communities to a wide array of chemicals that can impact their health. (healthybuilding.net)
  • Exposure studies have found that firefighters can absorb chemicals like benzene even when self-contained breathing apparatus (SCBA) are worn, suggesting that dermal absorption contributes to potentially harmful exposures. (cdc.gov)
  • To measure asphalt fume, air samples were collected and analyzed for the total particulate, the benzene-soluble particulate fraction, and polycyclic aromatic compounds (PACs). (cdc.gov)
  • Additionally, it was found that the irradiation of aromatic compounds such as formic acid and benzene caused the compounds to reach electronically excited states. (photonics.com)
  • Aromatic chemical compounds have an inherently high stability and often they are not easy to degrade. (photonics.com)
  • However, the high stability of aromatic compounds (explained by Hückel´s "4n+2" rule) exists only when the compounds are in their electronic ground states. (photonics.com)
  • According to Baird's rule, compounds that are aromatic in the ground state become antiaromatic and reactive in the excited state. (photonics.com)
  • Researchers can now use this rule to describe various behaviors of aromatic compounds when irradiated. (photonics.com)
  • EI-Sheekh MM, Ghareib MM, EL-Souod GW A (2011) IBiodegradation of Phenolic and Polycyclic Aromatic Compounds by Some Algae and Cyanobacteria. (omicsonline.org)
  • There are few examples of algae degrading aromatic compounds [ 5 , 6 ] examined the effects of the chlorophyte alga, Selenstrum capriconutum , on benzo pyrene. (omicsonline.org)
  • INTRODUCTION: Firefighters are exposed to volatile organic compounds (VOCs) during structural fire responses and training fires, several of which (e.g., benzene, acrolein, styrene) are known or probable carcinogens. (cdc.gov)
  • Dust, debris, and fumes from the WTC contained known and suspected carcinogens, including polycyclic aromatic hydrocarbons, asbestos, benzene, and dioxins," the researchers write in their article published in the Journal of the American Medical Association . (time.com)
  • To accomplish this, the structure of the starting stannacycle was altered with the addition of either one or two more flanking benzene rings to synthesize the naphthacene and pentacene boron analogues respectively. (wikipedia.org)
  • Two utility workers' exposures of 0.3 mg/m3 and 0.4 mg/m3 also exceeded the 12-hour adjusted ACGIH TLV for benzene-soluble particulate. (cdc.gov)
  • According to the American Cancer Society (ACS), other toxic exposures that are connected to firefighting include known carcinogens (cancer-causing substances) like perfluoroalkyl substances (PFAS) and diesel fumes, as well as arsenic, asbestos, benzene, cadmium, formaldehyde, silica, sulfuric acid, and many others. (nphic.org)
  • She was an early champion of the need to protect workers against occupational cancer hazards, especially those identified through her pioneering research on polycyclic aromatic hydrocarbon (PAH) and coal tar exposures in coke ovens. (who.int)
  • She served as the United States Assistant Secretary of Labor (as head of the Occupational Safety and Health Administration) from 1977 to 1981, overseeing the promulgation of standards to protect workers against hazards from exposures to benzene, cotton dust, and lead, among other agents. (who.int)
  • The starting materials are a benzenediacetaldehyde (a benzene ring with two aldehydes attached), and two equivalents of a phenyl alkyne. (rsc.org)
  • Phenanthrene is a planar polycyclic aromatic hydrocarbon, consisting of three fused benzene rings. (rsc.org)
  • Figure 1: the stylized planar structure of a benzene molecule (C 6 H 6 ). (astrochem.org)
  • In organic chemistry , a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon . (wikipedia.org)
  • The pink circular arcs represent the carbon-carbon aromatic bonds that form the "skeleton" of the molecule while the orange lines indicate the carbon-hydrogen covalent bonds that form the "decoration" around the exterior edge of the molecule. (astrochem.org)
  • On Earth and in the interstellar medium, a high temperature makes it easy for a hydrocarbon to lose one or more hydrogen atoms. (astrochem.org)
  • Hydrocarbon molecules with missing hydrogen atoms are more reactive and therefore more likely to capture carbon atoms in these collisions. (astrochem.org)
  • They occur in a diverse range of molecular structures and phases: they can be gases (such as methane and propane ), liquids (such as hexane and benzene ), low melting solids (such as paraffin wax and naphthalene ) or polymers (such as polyethylene and polystyrene ). (wikipedia.org)
  • First, they studied the addition of hydrosilanes to benzenes, naphthalene and gradually larger polycyclic aromatic hydrocarbons. (photonics.com)
  • Physical chemist Ralf Kaiser from the University of Hawaii and his colleagues conducted an experiment to see if frozen acetylene-a chemical compound used in welding-could be converted into complex organic molecules like the ones seen on Titan, specifically benzene and naphthalene. (gizmodo.com)
  • In sunlight, NOx, CO, unburned hydrocarbons, and evaporative emissions from gasoline react to form ground-level ozone, the principal component of smog. (env-econ.net)
  • Hydrocarbons with additives, such as gasoline, also are included. (cdc.gov)
  • 10% of total nonmethane organic carbon emission are aromatic hydrocarbons from the exhaust of gasoline-powered vehicles. (wikipedia.org)
  • Refiners blend aromatic hydrocarbons into gasoline to prevent the fuel from premature combustion (known as knocking), but ethanol has similar or superior anti-knock properties and is used as a substitute. (iowafarmbureau.com)
  • In their regularly released Fuel Trends Reports the U.S. Environmental Protection Agency specifically states that "ethanol's high octane value has allowed refiners to significantly reduce the aromatic content of the gasoline. (iowafarmbureau.com)
  • Air sampling for the benzene-soluble particulate fraction of asphalt showed a strander operator's time-weighed average (TWA) exposure as high as 0.8 mg/m3, a concentration which exceeded the American Conference of Governmental Industrial Hygienists' (ACGIH) time-adjusted Threshold Limit Value (TLV) of 0.25 mg/m3 for a 12-hour TWA concentration. (cdc.gov)
  • So we conducted a meta-analysis, and to explore the influence of low concentration benzene exposure on workers' genetic damage indicators using 3.25 mg/m 3 as the boundary value, in order to provide a basis for improved prevention and control of the harm from benzene exposure to the occupational population. (biomedcentral.com)
  • Occupational benzene exposure can affect multiple genetic damage indicators. (biomedcentral.com)
  • Even at an exposure concentration lower than 3.25 mg/m 3 , benzene exposure has genotoxicity. (biomedcentral.com)
  • As the official agency of the U.S. Department of Labor tasked with managing occupational safety and health, the Occupational Safety and Health Administration (OSHA) recommended in 1971 that the allowable exposure limit for benzene should be 32.5 mg/m 3 (10 ppm). (biomedcentral.com)
  • According to animals experiments, epidemiological studies and quantitative risk assessment, the occupational exposure limit of benzene recommended by the scientific expert group to European Union countries should be less than 3.25 mg/m 3 [ 11 ]. (biomedcentral.com)
  • Overall, 65% of paired samples (across all sample days) showed a post-shift increase in urinary levoglucosan and 5 firefighters were exposed to benzene at concentrations at or above the National Institute for Occupational Safety and Health (NIOSH) recommended exposure limit. (cdc.gov)
  • At the same time, increased attention should be focused on the health monitoring of the occupational population exposed to benzene, and health management should be strengthened to improve the health of the occupational population. (biomedcentral.com)
  • However, it is not required to warn consumers about these substances unless the benzene content is less than a thousand parts per million. (shareware-hut.com)
  • Workers who handle liquid asphalt are overexposed to asphalt fume (measured as benzene-soluble particulate). (cdc.gov)
  • The aromatic character of the molecule, in practical terms, refers to the fact that the benzene molecule's ring-shaped structure makes its carbon-carbon skeleton more stable when compared to other types of hydrocarbon molecules. (astrochem.org)
  • The benzene ring structure has a unique fascination for astrochemists who study the cosmic complexity of carbon because it can be generalized in multiple ways to produce enormous classes of potentially interstellar molecules. (astrochem.org)
  • In the interstellar medium, gaseous outflow from carbon-rich red giants is a major source of simple carbon-bearing molecules such as carbon monoxide and acetylene (C 2 H 2 , or if your prefer, "one-third" of a benzene ring). (astrochem.org)
  • A high temperature and a high gas density also promote frequent collisions between hydrocarbon molecules. (astrochem.org)
  • Structurally, they are related to acenes, linearly fused benzene rings. (wikipedia.org)
  • : 623 The most general form of saturated hydrocarbons, (whether linear or branched species, and whether with without one or more rings) is C n H 2 n +2(1- r ) , where r is the number of rings. (wikipedia.org)
  • hydrocarbon that are composed of multiple aromatic rings. (engineeringtoolbox.com)
  • Note that halogenating a hydrocarbon produces something that is not a hydrocarbon. (wikipedia.org)
  • I'm excited to see the research point to what we've suspected after years of working in this field - that replacing aromatics with ethanol indeed can have a direct positive impact on human health," said Dr. Steffen Mueller, principal economist at the Energy Resources Center, University of Illinois, Chicago. (iowafarmbureau.com)
  • The stabilized product was then treated with the sterically hindered base, tert-butyllithium in benzene and a stable anionic 9-boraanthracene compound was formed. (wikipedia.org)
  • In fact, exactly this type of interstellar emission has been observed in the form of the so-called "unidentified infrared bands", now commonly referred to as the "aromatic infrared bands" (see figure 4). (astrochem.org)
  • Benzene, an important component of organic solvents, is commonly used in industry. (biomedcentral.com)
  • Synthetic strategies to incorporate boron into a polycyclic carbon backbone aim to sterically protect the atom from nucleophilic attack while ensuring that favorable π-stacking interactions are still preserved to ensure electron mobility in the ring and compound stability within organic electronics. (wikipedia.org)