Respiratory catalysts

Health and Safety Factors. Animal-feeding studies of DMPPO itself have shown it to be nontoxic on ingestion. The solvents, catalyst, and monomers that are used to prepare the polymers, however, should be handled with caution. Eor example, for the preparation of DMPPO, the amines used as part of the catalyst are flammable toxic on ingestion, absorption, and inhalation and are also severe skin and respiratory irritants (see Amines). Toluene, a solvent for DMPPO, is not a highly toxic material in inhalation testing the TLV (71) is set at 375 mg/m, and the lowest toxic concentration is reported to be 100—200 ppm (72). Toxicity of 2,6-dimethylphenol is typical of alkylphenols (qv), eg, for mice, the acute dermal toxicity is LD q, 4000 mg/kg, whereas the acute oral toxicity is LD q, 980 mg/kg (73). The Noryl blends of DMPPO and polystyrene have PDA approval for reuse food apphcations. 

Tertiary Amine Catalysts. The Hquid tertiary aHphatic amines used as catalysts in the manufacture of polyurethanes can cause contact dermatitis and severe damage to the eye. Inhalation can produce moderate to severe irritation of the upper respiratory tracts and the lungs. Ventilation, protective clothing, and safety glasses are mandatory when handling these chemicals. 

Gasoline normally contains 0.04% by weight of sulfur, which is oxidized into sulfur dioxide in the engine. Automobiles contribute about 2% of manmade sources of sulfur in the air. It has been reported recently that oxidation catalysts may accelerate the oxidation of sulfur dioxide to sulfates, which is a more serious respiratory hazard than sulfur dioxide. It may be necessary to reduce the sulfur in gasoline. 

Studies on the particulate distributions from compressed natural gas (CNG) or diesel-fuelled engines with diesel oxidation catalyst (DOC) or partial diesel particle filter (pDPF) have also been performed. The results obtained are used as data for the model, to study the particle penetration into the human respiratory tracts. As a result, the number distribution of particles in different parts of lungs can be modeled [99-101]. Understanding the particle formation and their effects and finding the methods to ehminate the formed particulates from exhaust gas contribute to a cleaner urban environment and thus to a better quality of life. 

Heterogeneous catalysts are often located at the top of a reactor and manipulated with temporary handling equipment. To avoid exposure to toxic dust, local ventilation should be installed if this is impracticable, scrupulous use of personal protective equipment and rigid compliance with systems-of-work are essential. Respiratory equipment may include self-contained or line-fed breathing apparatus. 

Some nickel compounds may be irritant to skin and eyes and dermal contact with nickel can result in allergic contact dermatitis. Nickel carbonyl is extremely toxic by inhalation and should be handled in totally enclosed systems or with extremely efficient ventilation. Air monitors linked to alarms may be required to detect leaks. Respiratory equipment must be available for dealing with leaks. Biological checks (e.g. nickel in urine) should be considered for routine operations involving nickel catalysts. 

Platinum is used as a catalyst for nitric and sulphuric acid production, in petroleum refining and in catalytic mufflers to control air pollution. Platinum salts can cause respiratory complaints, asthma, and platinosis , an allergic response. Allergic dermatitis may also result from exposure to soluble platinum salts and once subjects have been sensitized it generally precludes continued occupational exposure at any level. The 8 hr TWA OEL for platinum metal is 5 mg/m but for soluble platinum salts it is only 0.002 mg/m. Handling precautions must include containment where possible, ventilation, personal protection, and the screening out of individuals who have become sensitized. 

The monomers, catalysts or hardeners, or plasticizers can include chemicals with the potential to irritate the skin, mucous membranes or respiratory tract. Some can promote skin or respiratory sensitization. The range of chemicals in use is extremely wide, so that reference should be made to the Materials Safety Data Sheet for each specific formulation or variation of it identifiable by reference to the supplier s proprietary name and code number. Some common resin types are summarized in Table 5.55. 

At the same time the interaction of superoxide with MPO may affect a total superoxide production by phagocytes. Thus, the superoxide adduct of MPO (Compound III) is probably quantitatively formed in PMA-stimulated human neutrophils [223]. Edwards and Swan [224] proposed that superoxide production regulate the respiratory burst of stimulated human neutrophils. It has also been suggested that the interaction of superoxide with HRP, MPO, and LPO resulted in the formation of Compound III by a two-step reaction [225]. Superoxide is able to react relatively rapidly with peroxidases and their catalytic intermediates. For example, the rate constant for reaction of superoxide with Fe(III)MPO is equal to 1.1-2.1 x 1061 mol 1 s 1 [226], and the rate constants for the reactions of Oi and HOO with HRP Compound I are equal to 1.6 x 106 and 2.2 x 1081 mol-1 s-1, respectively [227]. Thus, peroxidases may change their functions, from acting as prooxidant enzymes and the catalysts of free radical processes, and acquire antioxidant catalase properties as shown for HRP [228] and MPO [229]. In this case catalase activity depends on the two-electron oxidation of hydrogen peroxide by Compound I. 

The use of the reversion spectroscope enabled the position of the absorption bands to be determined accurately and to be conclusively distinguished from hemoglobin and myoglobin. It became clear that there were three different intracellular respiratory catalysts— cytochromes a,b,c—common to animals, bacteria, yeast and higher plants. In 1925 a preliminary scheme for the passage of O2 from blood to tissue was proposed ... 

The high activity that supported gold catalysts have shown for CO oxidation at ambient temperature makes them ideal candidates for use as respiratory protectors. A copper manganese oxide, Hopcalite, has been used for many years to remove CO in toxic environments. Thus, supported gold catalysts may be chosen in the future. 

Warburg and Christian showed that the color of this old yellow enzyme came from a flavin and proposed that its cyclic reduction and reoxidation played a role in cellular oxidation. When NADP+ was isolated the proposal was extended to encompass a respiratory chain. The two hydrogen carriers NADP+ and flavin would work in sequence to link dehydrogenation of glucose to the iron-containing catalyst that interacted with oxygen. While we still do not know the physiological function of the old yellow enzyme,b the concept of respiratory chain was correct. 

Small items such as organic acids (e.g., benzoyl chloride) and catalysts must be kept securely. They can be harmful if they are spilled. Their hazards include severe skin burns and damage to the eyes and respiratory systems. The MSDS for all items must be studied. 

Chromium(IV) dioxide is a tetravalent chromium compound with limited industrial application. It is used to make magnetic tape, as a catalyst in chemical reactions, and in ceramics (Hartford 1979). Because of its limited industrial uses, the potential for human exposure is less for chromium dioxide than for the more industrially important chromium(VI) and chromium(ni) compounds. A single chronic inhalation study in rats exposed to 15.5 mg chromium(IV)/m3 as chromium dioxide reported no respiratory, cardiovascular, gastrointestinal, hematological, hepatic, renal, or dermal/ocular effects (Lee et al. 1989). 

Adsorption is of great technological importance. Thus, some adsorbents are used on a large scale as desiccants, catalysts or catalyst supports others are used for the separation of gases, the purification of liquids, pollution control or for respiratory protection. In addition, adsorption phenomena play a vital role in many solid state reactions and biological mechanisms. 

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