Comparison of Domestic and International Technical Standards: Study on Improvement of Quality Control of Halogenated Fire Extinguishing Agents

Recently, the National Fire Protection Association (NFPA) announced the revised standards for halogen compound fire extinguishing facilities (NFPA 2001). Characteristically, it is strengthening the quality control standards for halogenated fire extinguishing agents, by presenting specific standards regarding the effects of not only their main ingredient, but also their additional ingredients on the human body. However, in Korea, halogen compound fire extinguishing agents used for firefighting purposes are managed by designating “purity” as the sole criteria for inspection. Considering that halogen compounds utilized for other purposes in Korea are undergoing quality control through various inspections for the safety of humans and the environment, it is evident that a higher level of quality control is required for halogen compounds used for firefighting purposes. Therefore, we would like to suggest a specific improvement plan to enhance safety while using halogenated fire extinguishing agents, through the comparative analysis of inspection criteria, and acceptance standards of corresponding domestic and foreign standards.

Transcriptomic evidence for versatile metabolic activities of mercury cycling microorganisms in brackish microbial mats

Methylmercury, biomagnifying through food chains, is highly toxic for aquatic life. Its production and degradation are largely driven by microbial transformations; however, diversity and metabolic activity of mercury transformers, resulting in methylmercury concentrations in environments, remain poorly understood. Microbial mats are thick biofilms where oxic and anoxic metabolisms cooccur, providing opportunities to investigate the complexity of the microbial mercury transformations over contrasted redox conditions. Here, we conducted a genome-resolved metagenomic and metatranscriptomic analysis to identify putative activity of mercury reducers, methylators and demethylators in microbial mats strongly contaminated by mercury. Our transcriptomic results revealed the major role of rare microorganisms in mercury cycling. Mercury methylators, mainly related to Desulfobacterota, expressed a large panel of metabolic activities in sulfur, iron, nitrogen, and halogen compound transformations, extending known activities of mercury methylators under suboxic to anoxic conditions. Methylmercury detoxification processes were dissociated in the microbial mats with methylmercury cleavage being carried out by sulfide-oxidizing Thiotrichaceae and Rhodobacteraceae populations, whereas mercury reducers included members of the Verrucomicrobia, Bacteroidetes, Gammaproteobacteria, and different populations of Rhodobacteraceae. However most of the mercury reduction was potentially carried out anaerobically by sulfur- and iron-reducing Desulfuromonadaceae, revising our understanding of mercury transformers ecophysiology.

Synthesis of 2-Hydroxynaphthyl Pyrazolines Containing Isoniazid Moiety: A Potential Antitubercular Agents

: The new series of pyrazolines derivatives containing isoniazid moiety were synthesized from 2-hydroxynaphthyl functionalized chalcones and isoniazid using sodium hydroxide as a base in 2-ethoxy ethanol.We are evaluated for their antitubercular activity against Mycobacterium tuberculosis strain (H37Rv) by Microplate Alamar Blue Assay (MABA) some of the tested compounds 3a, 3b, and 3c, were found to have higher antitubercular activity than the selected standard drugs, where as the compounds 3d, 3e, 3i and 3j found to have higher antitubercular activity than Streptomycin and same as that of drug Pyrazinamide and Ciprofloxacin. While remaining compound showed moderate activity. Where as it is found that the disubstituted halogen compound and electron withdrawing group on the phenyl ring are important substitution for increase in antitubercular activity.

Final Report on the Safety Assessment of Methyldibromo Glutaronitrile

The halogen compound Methyldibromo Glutaronitrile is used in a wide variety of cosmetics as a preservative. Concentrations in cosmetic formulations reportedly range from 0.0075 to 0.06%. The oral LD50 in rats is 640 mg/kg. Dogs on a diet of 4,000 ppm Methyldibromo Glutaronitrile for 13 weeks developed thyroid hyperplasia; those on a diet of 167 ppm exhibited no hyperplasia, although the thyroid glands were enlarged. Application of Methyldibromo Glutaronitrile at a level of 4.0 g/kg to the skin of rats for 21 days produced severe irritation. A concentration of 0.025% applied to the skin of rabbits in a 28-day dermal toxicity study resulted in only slight to moderate irritation. No evidence of sensitization was found in guinea pig studies, nor was photosensitization reported in mouse studies. No reproductive or developmental toxicity was noted in two rat studies. Methyldibromo Glutaronitrile was not mutagenic in a series of mammalian system tests. Clinical data using repeat insult patch testing (HRIPT) methods indicated that concentrations as low as 0.025% produced a positive reaction in a few individuals. To limit the possibility that formulations containing this ingredient will lead to sensitization, it was concluded that leave-on formulations should contain 0.025% Methyldibromo Glutaronitrile. Rinse-off formulations, because the duration of exposure is much less, are considered safe as currently used

The effect of hydrogen bromide on the products of the cool-flame combustion of n -pentane

Detailed studies have been made of the products of the cool-flame combustion of n -pentane in the absence and presence of small concentrations (2-6 vol. %) of added hydrogen bromide. In the uncatalysed reaction, acetone and acetaldehyde are the principal products formed at low temperatures during the induction period preceding the first cool flame but increasing amounts of C 5 alkenes and O-heterocycles start to be formed as the initial temperature is increased. The main effect of hydrogen bromide is to increase dramatically the yields of C 5 ketones at the expense of almost all the other products. The results indicate that in the absence of the halogen compound the principal fate of the initially formed pentylperoxy radicals is isomerisation to hydroperoxypentyl radicals. At 250 °C, the latter radicals mainly add on further oxygen and are eventually converted to pentanedihydroperoxides; at higher temperatures, the hydroperoxypentyl radicals tend increasingly to decompose directly to give principally pentenes and C 5 O-heterocycles. Hydrogen bromide alters the mechanism operating with binary mixtures primarily by providing a source of readily abstractable hydrogen and thus enhancing the formation of pentenemonohydroperoxides. Control experiments on the homogeneous breakdown of pentane-2-monohydroperoxide show that the principal decomposition product is pentan-2-one and thus confirm the probable importance of pentanemonohydroperoxides as intermediates in the HBr-promoted reaction. Studies of the chemical changes accompanying the passage of cool flames show that these vary considerably with the prevailing conditions as well as with the number of previous cool flames which have propagated through the mixture. Hydrogen bromide causes well-defined differences in the nature and distribution of the products of the combustion of n -pentane, although these changes are not as great as those brought about by the passage of cool flames which generally lead to considerable transient temperature rises in the system.

The influence of bromine compounds on the combustion of polyolefins II. Effects on the oxidative degradation

Investigations have been made of the thermal degradation of polyethylene and polypropylene in atmospheres containing oxygen and special attention has been paid to the influence of bromine on the various reactions concerned. Measurements in a static system show that neither bromine incorporated into the polymer nor hydrogen bromide in the surrounding gaseous atmosphere has any appreciable influence on the rate of mass loss, although the presence of the halogen compound does affect the nature of the volatile products formed during oxidation. Detailed chemical analysis has been carried out in a flow system in which molten polymer is injected into a flowing gas mixture of known oxygen content. The results obtained by different experimental procedures make it possible to determine the extents to which oxidation takes place in both the liquid and gaseous phases and to elucidate the action of hydrogen bromide on the reactions in the two phases. It is shown that with polyethylene and polypropylene considerable uptake of oxygen occurs in the liquid phase but some further oxidation generally takes place in the gas phase. With both the polymers hydrogen bromide decreases the overall oxygen uptake. However, with polyethylene the halogen compound promotes oxidation in the liquid phase but acts as a powerful inhibitor of subsequent oxidation in the gas phase. In contrast, with polypropylene, as little as 1 % of hydrogen bromide suppresses almost completely uptake of oxygen by the liquid but may promote oxidation in the gas phase to such an extent that ignition takes place above the molten polymer. The contrasting inhibiting and promoting effects of bromine on the oxidation of the two polymers are considered in the light of the probable elementary chemical steps involved and the relevance of the results to the mechanism of burning of polyolefins is discussed.