SciCombinator

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Concept: Benzene

172

BACKGROUND: Lignin is often overlooked in the valorization of lignocellulosic biomass, but lignin-based materials and chemicals represent potential value-added products for biorefineries that could significantly improve the economics of a biorefinery. Fluctuating crude oil prices and changing fuel specifications are some of the driving factors to develop new technologies that could be used to convert polymeric lignin into low molecular weight lignin and or monomeric aromatic feedstocks to assist in the displacement of the current products associated with the conversion of a whole barrel of oil. We present an approach to produce these chemicals based on the selective breakdown of lignin during ionic liquid pretreatment. RESULTS: The lignin breakdown products generated are found to be dependent on the starting biomass, and significant levels were generated on dissolution at 160[degree sign]C for 6 hrs. Guaiacol was produced on dissolution of biomass and technical lignins. Vanillin was produced on dissolution of kraft lignin and eucalytpus. Syringol and allyl guaiacol were the major products observed on dissolution of switchgrass and pine, respectively, whereas syringol and allyl syringol were obtained by dissolution of eucalyptus. Furthermore, it was observed that different lignin-derived products could be generated by tuning the process conditions. CONCLUSIONS: We have developed an ionic liquid based process that depolymerizes lignin and converts the low molecular weight lignin fractions into a variety of renewable chemicals from biomass. The generated chemicals (phenols, guaiacols, syringols, eugenol, catechols), their oxidized products (vanillin, vanillic acid, syringaldehyde) and their easily derivatized hydrocarbons (benzene, toluene, xylene, styrene, biphenyls and cyclohexane) already have relatively high market value as commodity and specialty chemicals, green building materials, nylons, and resins.

Concepts: Gasoline, Petroleum, Benzene, Lignin, Phenols, Vanillin, Guaiacol, Eugenol

170

The contaminant concentrations over which type strains of the species Dehalogenimonas alkenigignens and Dehalogenimonas lykanthroporepellens were able to reductively dechlorinate 1,2-dichloroethane (1,2-DCA), 1,2-dichloropropane (1,2-DCP), and 1,1,2-trichloroethane (1,1,2-TCA) were evaluated. Although initially isolated from an environment with much lower halogenated solvent concentrations, D. alkenigignens IP3-3T was found to reductively dehalogenate chlorinated alkanes at concentrations comparable to D. lykanthroporepellens BL-DC-9T. Both species dechlorinated 1,2-DCA, 1,2-DCP, and 1,1,2-TCA present at initial concentrations at least as high as 8.7, 4.0, and 3.5 mM, respectively. The ability of Dehalogenimonas spp. to carry out anaerobic reductive dechlorination even in the presence of high concentrations of chlorinated aliphatic alkanes has important implications for remediation of contaminated soil and groundwater.

Concepts: Ethanol, Water pollution, Benzene, Environmental remediation, Solution, Hexane, Environmental chemistry, Pentane

169

BACKGROUND: Bronchial asthma is one of the most prevalent diseases in Arab children. Environmental pollution has been suggested to be considered causative of asthma, nasal symptoms and bronchitis in both children and adult. The objectives of this study were to evaluate the association between serum polycyclic aromatic hydrocarbons (PAHs) levels, asthma and allergic outcomes among Saudi children aged up to 15 yrs. We hypothesized that increased serum PAHs are associated with allergy, asthma, or respiratory symptoms. METHODS: A total of 195 Saudi children (98 asthma pediatric patients and 97 healthy controls) were randomly selected from the Riyadh Cohort Study for inclusion. The diagnosis of Asthma was based on established pediatric diagnosis and medications taken. RESULTS: Asthma related markers showed highly significant differences between children with and without asthma. Thus IgE, resistin and IL-4 were significantly increased (p 0.004, 0.001 and 0.003, respectively) in children with asthma compared with non-asthma control subjects. GMCSF, IFN-gamma, IL-5, IL-8 and IL-10, on the other hand, were significantly decreased in children with asthma (p 0.003, 0.03, 0.001, 0.004 and 0.03, respectively). Strong associations between serum PAHs levels and biomarkers of childhood asthma were detected in Arabic children. Data confirmed the role of naphthalene, 4H-cyclobenta[def]phenanthrene, 1,2-benzanthracene, chrysene and benzo(e)acephenanthrylene in childhood asthma; levels of these PAHs were correlated with asthma related biomarkers including IgE, resistin, GMCSF and IFN-gamma as well as IL-4, IL-5, IL-8 and IL-10 cytokines. CONCLUSIONS: This data highlight the pivotal role of specific PAHs in childhood asthma.

Concepts: Asthma, Allergy, Polycyclic aromatic hydrocarbon, Benzene, Hydrocarbon, Aromaticity, Naphthalene, Chrysene

166

The dangers of lead exposure have been recognized for millennia. In the first century a.d., Dioscorides observed in his De Materia Medica that “lead makes the mind give way.” The first industrial hygiene act passed in the colonies, in 1723, prohibited the use of lead in the apparatus used to distill rum, because “the strong liquors and spirits that are distilld through leaden heads or pipes are judged on good grounds to be unwholsom and hurtful.” More recently, large amounts of lead were used to boost the octane rating of gasoline and improve the performance of paint. One would be . . .

Concepts: Gasoline, Ethanol, Benzene, Toluene, Octane, Century, Pedanius Dioscorides, Materia medica

138

Benzene, a hazardous component of gasoline, is a genotoxic class I human carcinogen. This study evaluated the genotoxic effects of occupational exposure to benzene in gasoline stations. Genotoxicity of exposure to benzene was assessed in peripheral blood leucocytes of 62 gasoline station workers and compared with an equal numbers of matched controls using total genomic DNA fragmentation, micronucleus test and cell viability test. An ambient air samples were collected and analyzed for Monitoring of benzene, toluene, ethyl benzene and xylene (BTEX) in work environment and control areas. DNA fragmentation, micronucleus and dead cells percent were significantly higher in exposed workers than controls. Level of benzene, Toluene, Ethyl benzene and xylene in the work environment were higher than the control areas and the permissible limits. Gasoline station workers occupationally exposed to benzene are susceptible to genotoxic effects indicated by increased DNA fragmentation, higher frequency of micronucleus and decreased leukocytes viability.

Concepts: Benzene, Toluene, Mutagen

115

58

Oil and gas development emits known hematological carcinogens, such as benzene, and increasingly occurs in residential areas. We explored whether residential proximity to oil and gas development was associated with risk for hematologic cancers using a registry-based case-control study design.

Concepts: Epidemiology, Cancer, Oncology, Leukemia, Benzene, Case-control study, Study design, Carcinogen

48

Polycyclic aromatic hydrocarbons (PAHs) are the main toxic compounds in natural bitumen, a fossil material used by modern and ancient societies around the world. The adverse health effects of PAHs on modern humans are well established, but their health impacts on past populations are unclear. It has previously been suggested that a prehistoric health decline among the native people living on the California Channel Islands may have been related to PAH exposure. Here, we assess the potential health risks of PAH exposure from the use and manufacture of bitumen-coated water bottles by ancient California Indian societies.

Concepts: Human, Petroleum, Carbon, Polycyclic aromatic hydrocarbon, Benzene, Hydrocarbon, Aromatic hydrocarbon, Naphthalene

44

Childhood leukemia may be associated with traffic-related environmental exposure to benzene, and additional data are needed. The Géolocalisation des Cancers Pédiatriques (GEOCAP) Study, a nationwide French case-control study, was designed to avoid selection bias due to differential participation and misclassification. The study compared the 2,760 childhood leukemia cases diagnosed in France between 2002 and 2007 (including 2,275 cases of acute lymphoblastic leukemia (ALL) and 418 cases of acute myeloblastic leukemia (AML)) with 30,000 contemporaneous child population controls. The residence addresses were precisely geocoded, and 3 indicators of residential proximity to traffic were considered. Estimates of benzene concentrations were also available for the Île-de-France region (including Paris). A 300-m increase in major road length within 150 m of the geocoded address was significantly associated with AML (odds ratio = 1.2, 95% confidence interval: 1.0, 1.4) but not with ALL (odds ratio = 1.0, 95% confidence interval: 0.9, 1.1), and the association was reinforced in the Île-de-France region when this indicator was combined with benzene estimates. These results, which were free from any participation bias and based on objectively determined indices of exposure, showed an increased incidence of AML associated with heavy-traffic road density near a child’s home. The results support a role for traffic-related benzene exposure in the etiology of childhood AML.

Concepts: Epidemiology, Cancer, Leukemia, Benzene, Acute myeloid leukemia, Acute lymphoblastic leukemia, Vincristine, Lymphoblast

39

Classification schemes for carcinogenicity based solely on hazard-identification such as the IARC monograph process and the UN system adopted in the EU have become outmoded. They are based on a concept developed in the 1970s that chemicals could be divided into two classes: carcinogens and non-carcinogens. Categorization in this way places into the same category chemicals and agents with widely differing potencies and modes of action. This is how eating processed meat can fall into the same category as sulfur mustard gas. Approaches based on hazard and risk characterization present an integrated and balanced picture of hazard, dose response and exposure and allow informed risk management decisions to be taken. Because a risk-based decision framework fully considers hazard in the context of dose, potency, and exposure the unintended downsides of a hazard only approach are avoided, e.g., health scares, unnecessary economic costs, loss of beneficial products, adoption of strategies with greater health costs, and the diversion of public funds into unnecessary research. An initiative to agree upon a standardized, internationally acceptable methodology for carcinogen assessment is needed now. The approach should incorporate principles and concepts of existing international consensus-based frameworks including the WHO IPCS mode of action framework.

Concepts: Decision making, Risk, Benzene, Carcinogen, Sulfur mustard, Chemical Weapons Convention, Chemical warfare, International Agency for Research on Cancer