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Risk Analysis : An Official Publication... Jul 2019We review approaches for characterizing "peak" exposures in epidemiologic studies and methods for incorporating peak exposure metrics in dose-response assessments that... (Review)
Review
We review approaches for characterizing "peak" exposures in epidemiologic studies and methods for incorporating peak exposure metrics in dose-response assessments that contribute to risk assessment. The focus was on potential etiologic relations between environmental chemical exposures and cancer risks. We searched the epidemiologic literature on environmental chemicals classified as carcinogens in which cancer risks were described in relation to "peak" exposures. These articles were evaluated to identify some of the challenges associated with defining and describing cancer risks in relation to peak exposures. We found that definitions of peak exposure varied considerably across studies. Of nine chemical agents included in our review of peak exposure, six had epidemiologic data used by the U.S. Environmental Protection Agency (US EPA) in dose-response assessments to derive inhalation unit risk values. These were benzene, formaldehyde, styrene, trichloroethylene, acrylonitrile, and ethylene oxide. All derived unit risks relied on cumulative exposure for dose-response estimation and none, to our knowledge, considered peak exposure metrics. This is not surprising, given the historical linear no-threshold default model (generally based on cumulative exposure) used in regulatory risk assessments. With newly proposed US EPA rule language, fuller consideration of alternative exposure and dose-response metrics will be supported. "Peak" exposure has not been consistently defined and rarely has been evaluated in epidemiologic studies of cancer risks. We recommend developing uniform definitions of "peak" exposure to facilitate fuller evaluation of dose response for environmental chemicals and cancer risks, especially where mechanistic understanding indicates that the dose response is unlikely linear and that short-term high-intensity exposures increase risk.
Topics: Acrylonitrile; Air Pollutants; Benzene; Environmental Exposure; Epidemiologic Studies; Ethylene Oxide; Formaldehyde; Humans; Leukemia; Lymphoma; Methylene Chloride; Neoplasms; Risk Assessment; Styrene; Trichloroethylene; United States; United States Environmental Protection Agency
PubMed: 30925210
DOI: 10.1111/risa.13294 -
ChemistryOpen Oct 2022Antibiotic resistance is now a growing threat to human health, further exacerbated by the lack of new antibiotics. We describe the practical synthesis of a series of...
Antibiotic resistance is now a growing threat to human health, further exacerbated by the lack of new antibiotics. We describe the practical synthesis of a series of substituted polyamine succinamides and branched polyamines that are potential new antibiotics against both Gram-positive and Gram-negative bacteria, including MRSA and Pseudomonas aeruginosa. They are prepared via 1,4-Michael addition of acrylonitrile and then hydrogenation of the nitrile functional groups to primary amines. They are built upon the framework of the naturally occurring polyamines thermine (3.3.3, norspermine) and spermine (3.4.3), homo- and heterodimeric polyamine succinic amides. Linking two of the same or different polyamines together via amide bonds can be achieved by introducing a carboxylic acid group on the first polyamine, then coupling that released carboxylic acid to a free primary amine in the second polyamine. If the addition of positive charges on the amino groups along the polyamine chains are a key factor in their antimicrobial activity against Gram-negative bacteria, then increasing them will increase the antimicrobial activity. Synthesising polyamine amide dimers will increase the total net positive charge compared to their monomers. The design and practical synthesis of such homo- and hetero-dimers of linear polyamines, spermine and norspermine, are reported. Several of these compounds do not display significant antibacterial activity against Gram-positive or Gram-negative bacteria, including MRSA and Pseudomonas aeruginosa. However, the most charged analogue, a branched polyamine carrying eight positive charges at physiological pH, displays antibiofilm activity with a 50 % reduction in PAO1 at 16-32 μg mL .
Topics: Humans; Polyamines; Spermine; Gram-Negative Bacteria; Anti-Bacterial Agents; Gram-Positive Bacteria; Acrylonitrile; Amides; Carboxylic Acids
PubMed: 36284254
DOI: 10.1002/open.202200147 -
Journal of Advanced Research Jan 2017The present investigation highlights the feasibility of a polymer grafting process to enhance the durability and flame retardancy of rice straw towards application as a...
The present investigation highlights the feasibility of a polymer grafting process to enhance the durability and flame retardancy of rice straw towards application as a low cost roofing material. The success of this grafting methodology was perceived to depend upon a bi-step pre-treatment process encompassing delignification and inorganic salts dispersion. Subsequently free radical polymer grafting of acrylonitrile onto rice straw was implemented by immersion mechanism initiated by oxalic acid-potassium permanganate initiator. The percentage of grafting, limiting oxygen index (LOI), biodegradability of the grafted rice straw and grafting yield percentage was estimated to be 57%, 27%, 0.02% and 136.67%, respectively. The weight loss of polymer grafted rice straw implied its less biodegradability over raw straw. Thus, the process of grafting contrived in the present analysis can be a promising and reliable technique for the efficient utilization of rice straw as an inexpensive roofing element through the augmentation of its durability and flame retardancy.
PubMed: 28116153
DOI: 10.1016/j.jare.2016.12.003 -
Chemical Science Oct 2020There is a widespread perception that the high level of selectivity witnessed in many Diels-Alder reactions is an intrinsic feature of the transformation. In contrast...
There is a widespread perception that the high level of selectivity witnessed in many Diels-Alder reactions is an intrinsic feature of the transformation. In contrast to expectations based upon this existing belief, the first experimental Diels-Alder reactions of a novel, deuterium-labeled 1,3-butadiene with commonly used mono-substituted alkenic dienophiles (acrolein, methyl vinyl ketone, acrylic acid, methyl acrylate, acrylamide and acrylonitrile) reveal kinetic : ratios close to 1 : 1. Maleonitrile, butenolide, α-methylene γ-butyrolactone, and -methylmaleimide behave differently, as does methyl vinyl ketone under Lewis acid catalysis. CBS-QB3 calculations incorporating solvent and temperature parameters give : product ratios that are in near quantitative agreement with these and earlier experimental findings. This work challenges the preconception of innate -selectivity by providing the first experimental evidence that the simplest Diels-Alder reactions are not -selective. Trends in behaviour are traced to steric and electronic effects in Diels-Alder transition structures, giving new insights into these fundamental processes.
PubMed: 34123213
DOI: 10.1039/d0sc04553e -
Acta Crystallographica. Section E,... Aug 2008The mol-ecular structure of the title compound, [Fe(C(5)H(5))(C(13)H(9)N(2))], (I), is analogous to that of the compound (Z)-3-ferrocenyl-2-phenyl-acrylonitrile [Cao &...
The mol-ecular structure of the title compound, [Fe(C(5)H(5))(C(13)H(9)N(2))], (I), is analogous to that of the compound (Z)-3-ferrocenyl-2-phenyl-acrylonitrile [Cao & Ye (2008). Acta Cryst. E64, m822], (II), with the pyridine ring in (I) replacing the benzene ring in (II). While the corresponding bond distances and angles in the two compounds show no significant differences, the two dihedral angles between the planes through the acrylonitrile group and the two rings attached to it (substituted Cp and pyridine) of 16.8 (4) and 20.1 (4)° in (I) are different from the corresponding dihedral angles [19.6 (3) and 6.5 (4)°] in (II). The unsubstituted ring is disordered over two positions, with site-occupancy factors of 0.70 (1) and 0.30 (1). The major and minor components of the disordered ring are almost coplanar and are also parallel to the substituted cyclo-penta-diene ring plane, with a dihedral angle of 0.3 (6)°.
PubMed: 21201613
DOI: 10.1107/S1600536808025531 -
Indian Journal of Microbiology Dec 2022Degradation of nitriles by mixed biofilms of nitrile-hydrolyzing bacteria 2 and gt 1 grown on basalt and carbon carriers, in a submerged packed-bed reactor was...
UNLABELLED
Degradation of nitriles by mixed biofilms of nitrile-hydrolyzing bacteria 2 and gt 1 grown on basalt and carbon carriers, in a submerged packed-bed reactor was studied. It was shown the formation of a massive mixed biofilm of 2 and gt 1 and the effective removal of nitriles and products of their degradation from the reaction medium. After the accumulation of carboxylic acid and some of the unprocessed substrate, the system adapts to 600-1000 h of biofilter operation, which is expressed in a decrease in the content of substrate and reaction products in the medium. The rate of acetonitrile and acrylonitrile utilization was 0.072-0.086 and 0.039-0.215 g/h, respectively, and acrylonitrile utilization with maximum rate was realized by a mixed biofilm on carbon fibers. Biofilms grown on mixed fibers in a "sandwich"-type reactor had the best characteristics for the transformation of aceto- and acrylonitrile (removal capacity of 99.6-99.9%, nitrile utilization rate of 0.080-0.095 g/h). Biofilms grown on basalt fiber with a diameter of 4-12 μm are also well suited for the degradation of acetonitrile (removal capacity of 100%, nitrile utilization rate of 0.086 g/h). The results of metagenomic analysis showed the resistance of 2 and gt 1 mixed biofilms against leaching from a biofilter and to competitive growth in an open system, indicating the advantages of biofilms over homogeneous biomass for wastewater treatment from nitrile compounds. Biofilms of two species of nitrile hydrolyzing bacteria on basalt and carbon fibers effectively purify water from nitriles in a submerged packed-bed reactor.
SUPPLEMENTARY INFORMATION
The online version contains supplementary material available at 10.1007/s12088-022-01030-z.
PubMed: 36458224
DOI: 10.1007/s12088-022-01030-z -
Polymers Sep 2021In this study, acrylonitrile butadiene styrene (ABS)/talc/graphene oxide/SEBS-g-MAH (ABS/Talc/GO/SEBS-g-MAH) and acrylonitrile butadiene styrene/graphene...
In this study, acrylonitrile butadiene styrene (ABS)/talc/graphene oxide/SEBS-g-MAH (ABS/Talc/GO/SEBS-g-MAH) and acrylonitrile butadiene styrene/graphene oxide/SEBS-g-MAH (ABS/GO/SEBS-g-MAH) composites were isolated with varying graphene oxide (0.5 to 2.0 phr) as a filler and SEBS-g-MAH as a compatibilizer (4 to 8 phr), with an ABS:talc ratio of 90:10 by percentage. The influences of graphene oxide and SEBS-g-MAH loading in ABS/talc composites were determined on the mechanical and thermal properties of the composites. It was found that the incorporation of talc reduces the stiffness of composites. The analyses of mechanical and thermal properties of composites revealed that the inclusion of graphene oxide as a filler and SEBS-g-MAH as a compatibilizer in the ABS polymer matrix significantly improved the mechanical and thermal properties. ABS/talc was prepared through melt mixing to study the fusion characteristic. The mechanical properties showed an increase of 30%, 15%, and 90% in tensile strength (TS), flexural strength (FS), and flexural modulus (FM), respectively. The impact strength (IS) resulted in comparable properties to ABS, and it was better than the ABS/talc composite due to the influence of talc in the composite that stiffens and reduces the extensibility of plastic. The incorporation of GO and SEBS-g-MA also shows a relatively higher thermal stability in both composites with and without talc. The finding of the present study reveals that the graphene oxide and SEBS-g-MAH could be utilized as a filler and a compatibilizer in ABS/talc composites to enhance the thermo-mechanical stability because of the superior interfacial adhesion between the matrix and filler.
PubMed: 34578081
DOI: 10.3390/polym13183180 -
Journal of Occupational Health Sep 2006Many new biomarkers are being studied, in addition to classical biomarkers, such as chemical substances and their metabolites in blood and urine and modified enzymes.... (Review)
Review
Many new biomarkers are being studied, in addition to classical biomarkers, such as chemical substances and their metabolites in blood and urine and modified enzymes. Among these new biomarkers, hemoglobin adducts are thought to be especially useful for the estimation of chemical exposures. We review here the use of biomarkers for monitoring exposures to nine substances, mainly focusing on PRTR class I designated chemical substances, styrene, phenyloxirane (styrene oxide), 4,4'-methylendiphenyl diisocyanate (MDI), 4,4'-methylendianiline (MDA), 1,3-butadiene, ethylene oxide, propylene oxide, acrylamide and acrylonitrile. Hemoglobin adduct levels were elevated after exposures to styrene, MDI, MDA, 1, 3-butadiene, ethylene oxide, acrylamide and acrylonitrile. Moreover, hemoglobin adducts of butadiene, ethylene oxide, acrylamide and acrylonitrile have several useful advantages. For example, the hemoglobin adduct of 1,3-butadiene is an even more useful biomarker of exposure than urinary metabolites, and in the case of ethylene oxide, even though the concentration of ethylene oxide-Hb in the blood of workers did not exceed the value of the German exposure equivalent, a significant difference in it was found between workers and a control group. Also hemoglobin adducts of acrylamide and acrylonitrile can reflect their exposures because there are no urinary metabolites of acrylamide and acrylonitrile that are useful for exposure assessment. In addition to these advantages, hemoglobin adducts are superior to DNA adducts with respect to the availability of large amounts, availability of methods for chemical identification, and well-defined life spans due to the absence of repair. Hemoglobin adducts can be effective biomarkers for assessing exposure to and the effects of chemicals.
Topics: Biomarkers; Hazardous Substances; Hemoglobins; Humans; Japan; Occupational Exposure
PubMed: 17053297
DOI: 10.1539/joh.48.314 -
Journal of Colloid and Interface Science Dec 2022Silver nanoclusters of five atoms (Ag) display outstanding catalytic activities for the deactivation of radicals. Using 2,2-diphenyl-1‑picrylhydrazyl (DPPH) radical as...
Silver nanoclusters of five atoms (Ag) display outstanding catalytic activities for the deactivation of radicals. Using 2,2-diphenyl-1‑picrylhydrazyl (DPPH) radical as a model system, we observed a fast radical reduction to DPPH anions using only [Ag] 3 to 4 orders of magnitude less than [DPPH]. Moreover, nanoclusters remain stable at the end of the reaction, and can deactivate again DPPH radicals at the same rate, indicating that they act as anti-radical catalysts. The radical scavenger catalytic activity of Ag proceeds selectively through the oxidation of methanol (used to dissolve the radical) to formaldehyde, which is supported by DFT calculations. The obtained catalytic rate constants are almost 2 orders of magnitude higher than oxidases, and more than 4 orders of magnitude larger than graphene quantum dots. We also show that Ag not only catalyze the reduction of radicals but also their oxidation, promoting the inhibition of the autoxidation mechanisms of hydrocarbon polymers, which are very sensitive to the presence of radicals. For this purpose, thin films of two industrially relevant polymers (polyisoprene and acrylonitrile-butadienestyrene copolymer), were exposed to standard simulated photo-ageing conditions in the presence of Ag. Using Attenuated Total Reflection-FTIR and DFT modeling we observed that, although Ag nanoclusters, with ≈ 15% surface coverage, do not totally inhibit the oxidation, they favour a decomposition that yields inactive products, in contrast with the more detrimental ketone formation pathway. These results not only open new possibilities for developing a post-process inhibition of polymer degradation, for which nowadays there are no efficient procedures, but also, they could be used as very efficient dual-redox catalytic radical scavengers for different industrial or biomedical purposes.
Topics: Acrylonitrile; Anions; Biphenyl Compounds; Formaldehyde; Graphite; Ketones; Methanol; Oxidation-Reduction; Oxidoreductases; Polymers; Silver
PubMed: 35932680
DOI: 10.1016/j.jcis.2022.07.133 -
Food Science & Nutrition May 2014Residual levels of 14 volatile substances, including 1,3-butadiene, acrylonitrile, benzene, ethylbenzene, and styrene, in 30 kitchen utensils made from...
Residual levels of 14 volatile substances, including 1,3-butadiene, acrylonitrile, benzene, ethylbenzene, and styrene, in 30 kitchen utensils made from acrylonitrile-butadiene-styrene resin (ABS) and acrylonitrile-styrene resin (AS) such as slicers, picks, cups, and lunch boxes in Japan were simultaneously determined using headspace gas chromatography/mass spectroscopy (HS-GC/MS). The maximum residual levels in the ABS and AS samples were found to be 2000 and 2800 μg/g of styrene, respectively. The residual levels of 1,3-butadiene ranged from 0.06 to 1.7 μg/g in ABS, and three of 15 ABS samples exceeded the regulatory limit for this compound as established by the European Union (EU). The residual levels of acrylonitrile ranged from 0.15 to 20 μg/g in ABS and from 19 to 180 μg/g in AS. The levels of this substance in seven ABS and six AS samples exceeded the limit set by the U.S. Food and Drug Administration (FDA). Furthermore, the levels of acrylonitrile in three AS samples exceeded the voluntary standard established by Japanese industries. These results clearly indicate that the residual levels of some volatile compounds are still high in ABS and AS kitchen utensils and further observations are needed.
PubMed: 24936293
DOI: 10.1002/fsn3.100