Respiratory chemical irritants

Alarie, Y. (1981a). Toxicological evaluation of airborne chemical irritants and allergens using respiratory reflex reactions. In Inhalation Toxicology and Technology (Leong, B.K.J., Ed.). Ann Arbor Science, Arm Arbor, pp. 207-231. 

These two definitions reflect two sides of the same situation. In this book, the term critical effect(s) will be used for the hazard/effect considered as being the essential one(s) for the purpose of the risk characterization, e.g., for the establishment of a health-based guidance value, permissible exposure level, or Reference Dose. It should be noted that the critical effect could be a local as well as a systemic effect. It should also be recognized that the critical effect for the establishment of a tolerable exposure level is not necessarily the most severe effect of the chemical substance. For example, although a substance may cause a serious effect such as liver necrosis, the critical effect for the establishment of, e.g., an occupational exposure limit could be a less serious effect such as respiratory tract irritation, because the irritation occurs at a lower exposure level. 

Toxicology. Wood dust exposure may cause eye and skin irritation, respiratory effects, and hardwood nasal cancer. Irritation of the skin and eyes resulting ftom contact with wood dust is relatively common and may result ftom mechanical action (e.g., irritation caused by bristles and splinters), chemical irritation, sensitization, or a combination of these factors. ... 

Systemic Effects.Silver nitrate and/or silver oxide have been reported to cause upper and lower respiratory tract irritation in humans when inhaled. In one case, inhalation of an unknown amount and chemical form of silver during work with molten silver ingots produced respiratory failure the day after exposure (Forycki et al. 1983). Without treatment the worker may have died. However, exposures such as this are not expected to be common and should be examined on a case by case basis. 

Most of the information on the effects of air pollution on humans comes from acute pollution episodes such as the ones in Donora and London. Illnesses may result from chemical irritation of the respiratory tract, with certain sensitive subpopulations being more affected (1) very young children, whose respiratory and circulatory systems are poorly developed, (2) the elderly, whose cardiorespiratory systems function poorly, and (3) people with cardiorespiratory diseases such as asthma, emphysema, and heart disease. Heavy smokers are also affected more adversely by air pollutants. In most cases the health problems are attributed to the combined action of particulates and sulfur dioxides (SO2) no one pollutant appears to be responsible. Table 4.2 summarizes some of the major air pollutants and their sources and effects. 

Think twice before pouring this stuff down your drain or spraying in your oven. It s a strong, caustic substance that causes severe corrosive damage to eyes, skin, and mucous membranes, as well as the mouth, throat, esophagus, and stomach. Blindness is reported in animals exposed to as little as 2% dilution for just one minute. Skin is typically damaged by 0.12% dilutions for a period of one hour. Tests with healthy volunteers exposed to the chemical in spray from oven cleaners showed that respiratory tract irritation developed in two to fifteen minutes. Sodium hydroxide is included as a toxic chemical on the EPA s Community Right-to-Know list. It is also a controlled substance in the workplace, and OSHA has set limitations on concentrations in the air. 

Acute inhalation LC50 values for chromium trioxide were 87 and 137 mg chromium(VI)/m3 for female and male rats, respectively (American Chrome and Chemicals 1989). Female rats were more sensitive than males to the lethal effects of most chromium(VI) compounds except sodium chromate, which was equally toxic in both sexes. Signs of toxicity included respiratory distress, irritation, and body weight depression (Gad et al. 1986). The LC50 values are recorded in Table 2-1 and plotted in Figure 2-1. 

IRPTC International Register of Potentially Toxic Chemicals Irritant A chemical substance that can cause an inflammatory reaction to the eye, skin, respiratory system. An irritant can cause an acute effect from a single high-level exposure or chronic effects from repeated exposures Itching An uncomfortable sensation in the skin... 

In some patients, this phase of mechanical obstruction is followed after some days or 3-4 weeks by a chemical reaction, presumably as the oil breaks down to irritant fatty acids, which cause exudation and hemorrhage. Interference with the production of lung surfactant can also occur and a marked intravascular cellular reaction has been described (70). The chemical irritative phase is marked by fever, cough with sputum (often blood) and a variable degree of respiratory distress there may even be tachycardia and hypotension. 

Abraham, M.H., Whiting, G.S., Alarie, Y., Morris, J.J., Taylor, P.J., Doherty, R.M., Taft, R.W. and Nielsen, G.D. (1990a). Hydrogen Bonding. Part 12. A New QSAR for Upper Respiratory Tract Irritation by Airborne Chemicals in Mice. Quant.Struct.-Act.Relat., 9,6-10. 

Large aerosolized particles (>10 j.m) deposit in the upper respiratory tract via inertial impaction. The majority (90%) of particles below the target size (<0.5 j,m) are inhaled and exhaled freely and rarely impact within the respiratory tract. To avoid triggering bronchospasm, aerosolized solutions should be isotonic with a neutral pH and should not contain chemical irritants such as benzalkonium, ethylenediamine tetraacetic acid (EDTA), chlorbutol, edetic acid or metabisulfite (Duvivier et al 1999b). 

Many chemicals cause irritation of the eyes, skin, and respiratory tract. In severe cases respiratory tract irritation can progress to acute respiratory distress syndrome (ARDS)/acute lung injury, which may be delayed in onset for up to 24-72 h in some cases. 

The main effects observed in animals following exposure to chlorofluorocarbons are CNS depression, respiratory tract irritation, rapid breathing, lung congestion, and microscopic liver changes. Cardiac dysrhythmias and mild chemical conjunctivitis have... 

Another postulated mechanism is an altered function of the central nervous and respiratory systems through an amplification of a nonspecific inflammatory response to low-level irritants (neurogenic inflammation hypothesis). This suggests that MCS may be initiated by the interaction of chemical irritants with sensory nerves or C-fiber neurons, a nonspecific response pathway. It is proposed that inhaled chemicals stimulate irritation receptors which activate sensory nerves to release mediators producing vasodilation, edema, and other manifestations of inflammation, leading to neurogenic inflammation. There is some evidence in animals for this theory. 

Pleural thickening and decreased pulmonary function have been associated with chronic exposure to titanium tetrachloride in titanium metal workers. Chronic inhalation exposure may result in upper respiratory tract irritation, chronic bronchitis, cough, bronchoconstriction, wheezing, chemical pneumonitis, or pulmonary edema in humans. Because titanium tetrachloride rapidly hydrolyzes upon contact with water, the negative findings from the limited studies performed are insufficient to reach any conclusion about titanium tetrachloride s ability to induce genotoxic effects. 

Pneumonia is an infection in the lungs caused by viruses, bacteria, fungi, or chemical irritants. Pneumonia starts as an upper respiratory infection as a result of acute pharyngitis or acute rhinitis and leads to a lower respiratory infection. Pneumonia is contagious and spreads via droplets in the air from coughing and sneezing. Symptoms of pneumonia can occur 3 days after the upper respiratory infection. 

Coughing is a common physiological method to clear the respiratory passages. If it becomes uncontrolled, then medication often can help. Such medications are called antitussives. The cough control center has been located in the medulla of the brain by electrical stimulation techniques. Normally, coughing is caused by chemical or mechanical irritation of the respiratory tract. Therefore, to stop a cough, the source of the respiratory tract irritation should be eliminated and the signal to the medulla interrupted. 

Respiratory disease may often be traced to an external source such as an inhaled allergen, pathogen, particulate matter, chemical irritant, or other, undefined material. Ideally, the resulting disease state would be abolished by removing the suspect material from the environment however, often this is not possible. We are left then to define effective drugs for the treatment of bronchial asthma, chronic bronchitis, chronic pulmonary emphysema, and a variety of other debilitating respiratory diseases. 

A. Liquid EDB is an irritant capable of oausing chemical bums. Inhalation of EDB vapor produces respiratory traot Irritation and delayed-onset pulmonary edema. 

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