Toxic hazards from mixtures

Undesirable emissions of toxic gases may occur as a result of mixing relatively common chemicals. Refer to Table 6.4. Chemicals which are incompatible in this way must be brought into contact only under strictly controlled conditions. 

F Flammable gases T Toxic products V Vigorous reaction 

Acetyl chloride CH3COCI Colourless, fuming, corrosive liquid Flash point 4°C When heated, emits phosgene Decomposes violently with water to produce heat and toxic fumes MCI 

Aluminium chloride (anhydrous) AICI3 Orange, yellow, grey or white powder which is a severe respiratory irritant and can cause skin/eye burns Reacts with air moisture to form corrosive HCI gas Violent reaction when a stream of water hits a large amount Do not use water in vicinity 

Benzoyl chloride C6H5COCI Colourless, fuming, corrosive liquid with a strong odour Combustible flash point 72°C Generates phosgene gas when heated Reacts strongly with water or water vapour, producing heat and toxic/corrosive fumes Use of water must be considered carefully 

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Table 7.4 Toxic hazards from incompatible chemical mixtures...

HD in the body is very slow, and repeated exposures produce a cumulative effect. Its toxic hazard is high for inhalation, ingestion, and skin and eye absorption, but the most common acute hazard is from liquid contact with eyes or skin. Agent HD is distilled H, it has been purified by washing and vacuum distillation to reduce sulfur impurities. Agent H is a mixture of 70% bis-(2-chloroethyl) sulfide and 30% sulfur impurities produced by unstable Levinstein process. 

Testing as a whole This may characterize the toxicity profile of the mixture and eventually verify the (presumed) safety or hazard from exposure to mixmre. One problem may be that incorporation of the test material in the diet at a sufficiently high dose may result in an unbalanced diet and nutritional deficiencies. Another problem is that most mixtures may change in chemical composition over time. 

Many of the hazards from the polymer industry arise from the monomers used as raw materials. Many monomers are reactive and flammable, with a tendency to form explosive vapor mixtures with air. All have a certain degree of toxicity vinyl chloride is a known human carcinogen. The combustion of many polymers may result in the evolution of toxic gases, such as hydrogen cyanide... 

This guideline covers only nonroutine or accidental events. Many hazardous events start with the discharge or loss of containment of a flammable and/or toxic material from a vessel or pipe. These discharges, which may take the form of vapor, liquid, solid, or multiphase vapor-liquid-solid mixtures, may be released into a confined area, such as a dike, building, or an equipment array, or into an open, unconfined area. The sources of these releases could be holes in vessels or pipelines, open pressure-relief devices, pipe ruptures, flange and seal leaks, or catastrophic vessel mptures. The range of releases is illustrated in Figure 2.1. 

An area which deserves special attention with respect to safety is the storage of liquid ammonia. In contrast to some other liquefied gases (e.g., LPG, LNG), ammonia is toxic and even a short exposure to concentrations of 2500 ppm may be fatal. The explosion hazard from air/ammonia mixtures is rather low, as the flammability limits [1334]-[1338], [1343] of 15-27% are rather narrow. The ignition temperature is 651 °C. Ammonia vapor at the boiling point of-33 °C has vapor density of ca. 70% of that of ambient air. However, ammonia and air, under certain conditions, can form mixtures which are denser than air, because the mixture is at lower temperature due to evaporation of ammonia. On accidental release, the resulting cloud can contain a mist of liquid ammonia, and the density of the cloud may be greater than that of air [1334]-[1344], This behavior has to be taken into account in dispersion models. 

EPA recommends three approaches (1) if the toxicity data on mixture of concern are available, the quantitative risk assessment is done directly form these preferred data (2) when toxicity data are not available for the mixture of concern, data of a sufficiently similar mixture can be used to derive quantitative risk assessment for mixture of concern and (3) if the data are not available for both mixture of concern and the similar mixture, mixture effects can be evaluated from the toxicity data of components. According to EPA, the dose-additive models reasonably predict the systemic toxicity of mixtures composed of similar (dose addition) and dissimilar (response addition) compounds. Therefore, the potential health risk of a mixture can be estimated using a hazard index (HI) derived by summation of the ratios of the actual human exposure level to estimated maximum acceptable level of each toxicant. A HI near to unity is suggestive of concern for public health. This approach will hold true for the mixtures that do not deviate from additivity and do not consider the mode of action of chemicals. Modifications of the standard HI approach are being developed to take account of the data on interactions. 

Listed as toxic waste from nonspecific sources spent nonhalogenated solvents such as carbon disulfide spent solvent mixtures containing a total of at least 10% (by volume) of carbon disulfide before use and still bottoms from the recovery of above nonhalogenated solvent and solvent mixtures this item was listed as a hazardous waste due to its toxicity and ignitability Yes EPA 1995h (46 FR 4618)... 

Harris et al. 1984). The inhalation hazard from its vapors is therefore lower than that of mustard gas. Contact with the body can result in severe local injury. It can penetrate through skin, causing inflammation and blistering, which are difficult to heal. Like mustard gas, this substance also exhibits delayed clinical symptoms at low concentrations. There is no report of carcinogenicity. In chemical warfare, it is used in combination with mustard gas. Such a combined mixture is known as HT. The toxicity and vesicant action of HT are greater than those of its components. The mixture sohdifies at a lower temperature and is more persistent than the mustard gas alone. 

Skin irritation can be produced by nonimmune-mediated idiosyncratic cutaneous reactions resulting from cumulative toxicity, overdose, drug interactions, and metabolic alterations (Lee and Thompson, 2006). RhE skin irritation tests (SIT) have been validated and adopted by OECD as TG 439 for determining the irritation hazard from topical exposure to chemicals and mixtures (Kandarova et al., 2009 OECD, 2009). TG 439 is based on the ability of irritant chemicals to penetrate the stratum comeum and produce cytotoxicity in the underlying cell layers. The TG classifies test substances as either irritating or nonirritating based on results of the MTT viability assay. 

As would be expected from their chemical reactivity and substantial volatility, TDI mixtures can represent a serious toxic hazard in use, having a marked effect on the respiratory system and the skin, and care is very necessary in handling if damage to health is to be avoided. On the other... 

Table A.1.2—Conversion From Experimentally Obtained Acute Toxicity Range Values (or Acute Toxicity Hazard Categories) to Acute Toxicity Point Estimates for Use in the Formulas for the Classification of Mixtures...

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