Acute local effects

Substances can produce harmful effects by physical as well as chemical means. This is especially true of liquefied gases, which can evaporate so rapidly as to cause a drastic lowering of the temperature of the eyes or skin, or even frostbite. 

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Phenol poisoning can occur in humans after skin absorption, inhalation of vapours or ingestion. Acute local effects are severe tissue irritation and necrosis. At high doses, the most prominent systemic effect is central nervous system depression (lARC, 1989). 

May assess only the short-term site of application or immediate structural alterations produced by agents however, specific in v/Vo tests may only be intended to evaluate acute local effects, so this may be a purposeful test system limitation Require stringent technician training and monitoring (particularly because of the subjective nature of evaluation)... 

Workers Inhalation Acute local effects, Acute systemic effects 68mg/m3... 

Skin. The skin may become contaminated accidentally or, in some cases, materials may be deHberately appHed. Skin is a principal route of exposure in the industrial environment. Local effects that are produced include acute or chronic inflammation, allergic reactions, and neoplasia. The skin may also act as a significant route for the absorption of systemicaHy toxic materials. Eactors influencing the amount of material absorbed include the site of contamination, integrity of the skin, temperature, formulation of the material, and physicochemical characteristics, including charge, molecular weight, and hydrophilic and lipophilic characteristics. Determinants of percutaneous absorption and toxicity have been reviewed (32—35,42,43,46—49). 

The likelihood that materials will produce local effects in the respiratory tract depends on their physical and chemical properties, solubiHty, reactivity with fluid-lining layers of the respiratory tract, reactivity with local tissue components, and (in the case of particulates) the site of deposition. Depending on the nature of the material, and the conditions of the exposure, the types of local response produced include acute inflammation and damage, chronic... 

The two examples just given are of localized effects associated with the acute toxicity of DDT and DDD to organisms in higher trophic levels. A more wide-ranging toxic effect associated with population decline was eggshell thinning caused by the relatively high levels of p,p -DDE in some predatory birds (see Table 5.7). 

The effect differs according to time and place. So far as the time effect is concerned, there is a need to distinguish acute effect, which appears a short while after the substance penetration, from the long term or chronic effect, for which effects can be identified after several years of exposure. The action can be local, ie contact point with the substance, or systemic , reaching organs that are distant from the penetration point.The local effect affects skin and eyes and/or mucous membranes, especially the inhalation ones. The local effects are irritant and sensitive. 

Acute biological effects of the Chernobyl accident on local natural resources were documented by Sokolov et al. (1990). They concluded that the most sensitive ecosystems affected at Chernobyl were the soil fauna and pine forest communities and that the bulk of the terrestrial vertebrate community was not adversely affected by released ionizing radiation. Pine forests seemed to be the most sensitive ecosystem. One stand of 400 ha of Pirns silvestris died and probably received a dose of 80 to 100 Gy other stands experienced heavy mortality of 10- to 12-year-old trees and up to 95% necrotization of young shoots. These pines received an estimated dose of 8 to 10 Gy. Abnormal top shoots developed in some Pirns, and these probably received 3 to 4 Gy. In contrast, leafed trees such as birch, oak, and aspen in the Chernobyl Atomic Power Station zone survived undamaged, probably because they are about 10 times more radioresistant than pines. There was no increase in the mutation rate of the spiderwort, (Arabidopsis thaliana) a radiosensitive plant, suggesting that the dose rate was less than 0.05 Gy/h in the Chernobyl locale. 

Most certainly the greatest culprit in excess nutrients is agriculture. Nevertheless, urban areas contribute a grossly disproportionate share of these chemicals (Table 4.5), creating acute local stream problems. Lawn fertilization contributes to this effect, though to a degree not yet fully determined. 

Local anesthetics have poorly understood effects on inflammation at sites of injury, and these anti-inflammatory effects may contribute to improved pain control in some chronic pain syndromes. At the concentrations used in spinal anesthesia, local anesthetics can inhibit transmission via substance P (neurokinin-1), NMDA, and AMPA receptors in the secondary afferent neurons (Figure 26-1). These effects may contribute to the analgesia achieved by subarachnoid administration. Local anesthetics can also be shown to block a variety of other ion channels, including nicotinic acetylcholine channels in the spinal cord. However, there is no convincing evidence that this mechanism is important in the acute clinical effects of these drugs. High concentrations of local anesthetics in the subarachnoid space can interfere with intra-axonal transport and calcium homeostasis, contributing to potential spinal toxicity. 

Uses Asthma in pts requiring chronic steroid therapy relieve seasonal/perennial allergic rhinitis Action Topical steroid Dose Adults. Met-dose inhal 2 inhal bid (max 8/d) Nasal 2 sprays/nostril bid (max 8/d) Peds >6y. Met-dose inhal 2 inhal bid (max 4/d) Nasal 1-2 sprays/nostril bid (max 4/d) Caution [C, ] w/ adrenal insuff Contra Status asdimaticus, viral, TB, fungal, bacterial Infxn Disp Inhaler SE Tach, bitter taste, local effects, oral candidiasis EMS Not for acute asthma, use inhaled [3-agonists OD Unlikely... 

Because of its powerfiil vasodilator action sodium nitroprusside is often used to treat vascular emergencies associated with hypertensive crisis. Since this compound shows some anti-platelet activity both in vitro and in vivo (Levin et al 1982, Hines and Barash 1989) its acute clinical effects may also be mediated, in part, through inhibition of platelet function. Recently, sodium nitroprusside was administered intrapericardially to treat experimentally induced coronary Arombosis in dogs (Willerson et al 1996). As this route of administration of sodium nitroprusside produced less vasodilatation than systemic one, localized administration of this dmg may offer new therapeutic possibilities for the treatment of the coronary thrombosis. 

In humans, the pulmonary drug deposition of HFA-beclometasone is superior to CFC-beclometasone and is improved by 10-fold in some studies (Sears 1995). Equivalent improvements in asthma control are seen with half of the daily dose of HFA-beclometasone compared with CFC-beclometasone. The greater systemic availability of HFA-beclometasone does not increase adrenal suppression the adrenal effects and acute local tolerability are comparable to that of the CFC formulation at the same dose. Equivalent efficacy at a lower dose and equivalent safety at the same dose indicate a more favorable risk-benefit ratio for HFA-beclometasone. Comparative studies of HFA- and CFC-beclometasone have not been performed in horses. In theory, the enhanced drug delivery and efficacy of HFA-beclometasone may explain, in part, why relatively low doses of beclometasone are therapeutically effective in heaves-affected horses, compared with standard therapeutic doses in asthmatic humans. 

The gas leak had devastating effects on the exposed population. Over 200000 residents (that comprised about one-fourth of the total population of city of Bhopal) were exposed to MIC and other related toxic gases released from the plant. Most of these residents were from the poor class and were living in the immediate surroundings of the Union carbide plant. The human mortality is estimated to be between 2500 and 5000 from this accident. Respiratory failure due to MIC inhalation was the principal cause of death. MIC caused bronchial necrosis and pulmonary edema. Within the first 24 h after the accident, 90 000 patients were admitted in local hospitals and clinics with multiple symptoms of respiratory distress, breathlessness, choking, cough, chest pain, and hemoptysis. Acute ophthalmic effects were also reported with severe eye irritation and watering of the eyes. 

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