Respiratory system sensitization mixtures

Similarly, no respiratory effects were found in rats and mice chronically exposed by diet to 5/ 10" and 1.3 10s g/kg/day of 2,7-DCDD, respectively (NCI/NTP 1979a). In contrast, rats exposed chronically by gavage to a mixture of 1,2,3,6,7,8-HxCDD and 1,2,3,7,8,9-HxCDD at 0.18, 0.34, and 0.7 g/kg/day had a dose-related increased incidence of adenomatous hyperplastic lesions in terminal bronchioles and adjacent alveoli of both males and females no such effects were found in mice exposed chronically to 0.7 g/kg/day of that same mixture (NCI/NTP 1980). The existing information suggests that in animals, the respiratory system is not a sensitive target for CDDs toxicity via oral exposure. 

Information regarding levels of chromium(III) compounds that result in death is available only for the oral route. Systemic effects of acute- and intermediate-duration inhalation exposure to chromium(III) are limited to the respiratory system. Information on systemic effects of chronic inhalation exposure to chromium(III) is limited to a study that used a mixture of chromium(VI) and chromium(III). Studies of intermediate- and chronic duration oral exposure to chromium(III) failed to find any systemic, neurological, developmental, reproductive, or carcinogenic effects. The immunological and genotoxic effects of chromium(III) in animals have not been tested by the oral route. Information regarding effects of dermal exposure of animals to chromium(III) is limited to a study of skin ulceration after acute exposure and dermal sensitization tests. 

Formaldehyde is a major contributor to many cases of sick building syndrome. It is a very toxic chemical that is corrosive to the skin, eyes, and the respiratory system. Acute or chronic exposure can result in difficulty breathing and even brief exposures can induce asthmatic reactions in sensitized individuals. 13 Exposures to mixtures of formaldehyde and lipophilic chemicals can result in unanticipated toxic effects. 14 Formaldehyde is an animal carcinogen, a suspected human nasal cancer carcinogen 29 and suspected human leukemogen. 3°1... 

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. ... 

OECD has also published a document on a Harmonised integrated classification system for human health and environmental hazards of chemical substances and mixtures (OECD 2001b). Chapter 2.4 addresses a harmonized system for the classification of chemicals, which cause respiratory or skin sensitization. 

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