Nitrogen oxides, respiratory toxicity

Upper respiratory toxicants include hydrogen halides (hydrogen chloride, hydrogen bromide), oxides (nitrogen oxides, sulfur oxides, sodium oxide), and hydroxides (ammonium hydroxide, sodium dusts, and potassium hydroxides). Lower respiratory toxicants include monomers (such as acrylonitrile), halides (fluorine, chlorine, bromine), and other miscellaneous... 

The Clean Air Act recognizes a number of so-called primary air pollutants, and the EPA has established standards for these substances. Ozone, nitrogen oxides, and sulfur dioxide are among these (the others are carbon monoxide and lead, discussed below, and total suspended particulates ). The EPA s standard for ozone is 0.08 parts of the gas per million parts of air (0.08 ppm), averaged over eight hours. Standards also exist for the oxides of sulfur and nitrogen. These are designed to prevent chronic respiratory toxicity of any kind. 

In the event of a major plant accident, large quantities of nitrogen oxides could be released into the atmosphere and product nitric acid may well be released to the drains. There is little that can be done to provide for such a situation. The emphasis would be on dilution of any liquid wastes expelled. It would be left to the prevailing winds to disperse the nitrogen oxide cloud. Fortunately this gas cloud is not flammable, but it is highly toxic. Nitrogen oxide fumes either from nitric acid or from process gases may have a deceptive delayed action. The victim may feel no pain or discomfort at the time of the low-level inhalation, or for up to 48 hours thereafter, but then serious respiratory and cardiac problems can occur. 

NO) and nitric oxide or nitrogen dioxide (NO2). NO is produced during high-temperature combustion processes and comes principally from motor vehicle exhaust and stationary sources. NO2 derives from the oxidation of NO in the atmosphere and represents an intermediate in the production of several secondary pollutants as ozone. Nitrogen dioxide is highly oxidant and toxic it can irritate the lungs and lower resistance to respiratory infections. 

Handling, Storage, and Precautions the solid is irritating to eyes, mucus membranes, and respiratory tract, and physical contact should be avoided. Combustion produces toxic byproducts including nitrogen oxides. Cold storage in air-tight containers is recommended. Use in a fume hood. 

If nitrogen or sulphur is present in the fuel then the mixture of combustion products may include oxides of these elements. In the absence of excess oxygen incomplete oxidation occurs to produce partially oxidized carbon compounds such as aldehydes, ketones, phenols, and carbon monoxide. Carbon monoxide is extremely toxic and some of the other compounds are respiratory irritants. 

Nitrite is also an important source of nitric oxide, molecule that could rapidly react with superoxide to form peroxynitrite (ONOO ), a potent cytokine which is very reactive (Kohn et al., 2002). Reactive species of oxygen and nitrogen could initiate a toxic oxidative chain, including lipid peroxidation, protein oxidation, directly inhibiting some enzymes from the mitochondrial respiratory chain, and causing dysfunctions of the antioxidant defense systems. 

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