Respiratory system irritant mixtures

Not all mixtures that are toxic to the respiratory system are mixtures of lipophiles and hydrophiles. In some instances, irritant chemicals react to produce more toxic species. Chloramine-induced pneumonitis from the mixing of household ammonia and bleach is an example of this phenomenon. 100 101 Household ammonia cleaner is usually a 5-10% aqueous solution of ammonia. Household bleach is generally a 5.25% solution of sodium hypochlorite. At these concentrations, these chemicals alone act as respiratory irritants. When mixed together, however, they react to form monochloroamine, dichloroamine, and trichloroamine as shown in Fig. 17.1. Chloramines are far more toxic than either hypochlorite or ammonia and are capable of producing inflammation and edema of the respiratory system. Case 14 is an example of the toxicity of chloramines. 

Most of the chemicals listed produce vapors that target the respiratory system and the CNS. All are dangerous if ingested and all are irritating or corrosive to dermal and eye tissues. Mixtures of either alkalis or acids with lipophilic solvents (e.g., toluene, aliphatic hydrocarbons) produce enhanced burn effects. Skin and eyes exposed to chemicals that can burn... 

Chemicals and chemical mixtures that attack the respiratory system are categorized as corrosives, irritants, and sensitizers. Though the term irritant is often applied in the literature to chemicals that are either corrosives or irritants, the definitions used here are those that follow. These definitions are identical to those used by toxicologists and regulatory agencies to classify the hazards due to chemical inhalation. 

This section is devoted to chemical mixtures that are respiratory irritants. Irritants do not induce immunochemical responses, and irritation in non-sensitized individuals generally leads to slower, less serious respiratory responses and usually requires higher doses of toxicants to produce symptoms than in sensitized people. Irritant-induced inflammation responses (e.g., bronchial hyperactivity) can be severe and prolonged but, by definition, do not result in sensitization of those so exposed. Mixtures of lipo-philes and hydrophiles induce irritant respiratory system responses at concentration levels that are below those for the single chemicals. This phenomenon is well demonstrated by exposures in sick buildings. ... 

Inhalation Exposure. Only one inhalation MRL, a chronic MRL for //-hexane, is available for this combined fraction this is listed in Table 6-8. //-Hexane produces a characteristic peripheral nephropathy in humans and animals the chronic MRL is based on this effect in humans. Commercial hexane, which contains //-hexane plus other C6 branched chain and cyclic alkanes (see Table 6-8), also has been shown to cause this effect in animals, due to its content of //-hexane (IRDC 1981) (see Section 6.2.4.1). The non n-hexane portion of the mixture does not. In addition, the non //-hexane constituents of this combined fraction do not appear to cause peripheral neuropathy when tested singly although, like //-hexane, they do cause neurological effects (depression of the central nervous system). //-Hexane and commercial hexane are respiratory irritants. Commercial hexane has undergone extensive recent testing as part of an EPA Test Rule under TSCA Section 4. However, until the database for commercial hexane can be more fully evaluated, the chronic MRL for //-hexane has been determined to be the most appropriate surrogate for a health guidance value for this fraction. 

Benzene is primarily an inhalation hazard. Systemic absorption may cause depression of the hematopoietic system, pancytopenia, aplastic anemia, and leukemia. Inhalation of high concentrations can affect central nervous system function. Aspiration of small amounts of liquid benzene immediately causes pulmonary edema and hemorrhage of pulmonary tissue. There is some absorption through the skin. Absorption may be more rapid in the case of abraded skin, and benzene may be more readily absorbed if it is present in a mixture or as a contaminant in solvents which are readily absorbed. The defatting adion of benzene may produce primary irritation due to repeated or prolonged contact with the skin. High concentrations are irritating to the eyes and the mucous membrances of the nose, and respiratory tract. 

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