Pulmonary tract

During occupational exposure, respiratory absorption of soluble and insoluble nickel compounds is the major route of entry, with gastrointestinal absorption secondary (WHO 1991). Inhalation exposure studies of nickel in humans and test animals show that nickel localizes in the lungs, with much lower levels in liver and kidneys (USPHS 1993). About half the inhaled nickel is deposited on bronchial mucosa and swept upward in mucous to be swallowed about 25% of the inhaled nickel is deposited in the pulmonary parenchyma (NAS 1975). The relative amount of inhaled nickel absorbed from the pulmonary tract is dependent on the chemical and physical properties of the nickel compound (USEPA 1986). Pulmonary absorption into the blood is greatest for nickel carbonyl vapor about half the inhaled amount is absorbed (USEPA 1980). Nickel in particulate matter is absorbed from the pulmonary tract to a lesser degree than nickel carbonyl however, smaller particles are absorbed more readily than larger ones (USEPA 1980). Large nickel particles (>2 pm in diameter) are deposited in the upper respiratory tract smaller particles tend to enter the lower respiratory tract. In humans, 35% of the inhaled nickel is absorbed into the blood from the respiratory tract the remainder is either swallowed or expectorated. Soluble nickel compounds... 

Effects on immune function have not been evaluated in animals following any route of exposure. There was an increased frequency of pulmonary tract infections in animals following inhalation and oral exposures... 

Fig. 9.11. Particle deposition in pulmonary tract as a function of particle diameter.

Observe normal precautions appropriate to the circumstances and quantity of material handled. Sodium acetate is a mild skin and eye irritant gloves and eye protection are recommended. On exposure, wash eyes and skin with large amounts of water. Inhalation of dust may cause pulmonary tract problems. When heated to decomposition, sodium acetate emits toxic fumes of Na02.< ... 

The immune system is characterized by a unique distribution, and many of its components are located close to the principal sites of absorption, including the gastrointestinal tract, the pulmonary tract, and the skin. Therefore, the immune system is in a position to be exposed to potentially high concentrations of drugs and chemicals. This phenomenon is especially important in hypersensitivity responses where the primary portal of entry of the hapten can determine the specific site of the reaction. 

One of the best understood biosynthetic pathways for terpenoids is the biosynthesis for menthol in mint plants. All the enzymes are identified, cloned, and characterized [43]. Menthol plays an important role as aroma in food, cigarettes, and medications for the pulmonary tract and in cosmetics. Improvements of yield or... 

As noted in the previous chapter, respiratory uptake of Pb entails both a deposition step for Pb-bearing inhaled aerosols and an uptake step in the pulmonary tract, the uptake rate being a function of particle size and chemical composition. The lEUBK model employs a 30% deposition of Pb in the lung, and assumes there is 100% uptake of that fraction. Given the very low uptake of divalent inorganic lead from skin surfaces, a dermal uptake component is not included in this model. 

The uptake rates for Pb from the pulmonary and GI tracts differ in some major ways from values used in the lEUBK or the Leggett models. Like the other models, however, it accommodates the age-dependent Gl uptake differences in exposed humans. Respiratory uptake of inhaled air Pb is taken to be independent of age. This model assumes 50% uptake of the amounts of inhaled Pb versus the lEUBK s 100% uptake of the initial 30% deposition in the pulmonary tract under ambient conditions. 

Phosphine (PHj), a colorless gas that undergoes autoignition at 100°C, is a potential hazard in industrial processes and in the laboratory. Symptoms of poisoning from potentially fatal phosphine gas include pulmonary tract irritation, depression of the central nervous system, fatigue, vomiting, and difficult, painful breathing. 

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