LECTURES IN OCCUPATIONAL DISEASES

Transcription

1 LECTURES IN OCCUPATIONAL DISEASES الدكتورة سجال فاضل فرھود الجبوري M.B.Ch.B.(Babylon University) M.Sc.(Community Medicine-Al Nahrain) Asbestosis Asbestosis is a chronic inflammatory medical condition affecting the parenchymal tissue of the lungs. It occurs after long-term, heavy exposure to asbestos, e.g. in mining, and is therefore regarded as an occupational lung disease. Sufferers have severe dyspnea and are at an increased risk regarding several different types of lung cancer. Signs and symptoms The primary symptom of asbestosis is generally the slow onset of shortness of breath on exertion. In severe, advanced cases, this may lead to respiratory failure. Coughing is not usually a typical symptom, unless the patient has other, concomitant respiratory tract diseases. People with extensive occupational exposure to the mining, manufacturing, handling or removal of asbestos are at risk of developing asbestosis. There is also an increased risk of lung cancer and mesothelioma. Asbestosis and lung cancer require prolonged exposure to asbestos. However, cases of mesothelioma have been documented with even 1-3 months of exposure, and only indirect exposure (through air ventilation system.) Most cases of asbestosis do not become apparent until 5-10 years after the initial exposure to the material. Pathogenesis

2 Asbestosis is the scarring of lung tissue (around terminal bronchioles and alveolar ducts) resulting from the inhalation of asbestos fibers. There are two types of fibers, amphibole (thin and straight) and serpentine (curved). The former are primarily responsible for human disease as they are able to penetrate deeply into the lungs. When such fibers reach the alveoli in the lung, where oxygen is transferred into the blood, the foreign bodies (asbestos fibers) cause the activation of the lung's local immune system and provoke an inflammatory reaction. This inflammatory reaction can be described as chronic rather than acute, with a slow ongoing progression of the immune system in an attempt to eliminate the foreign fibres. Macrophages phagocytose the fibers and stimulate fibroblasts to deposit connective tissue. Due to the asbestos fibres' natural resistance to digestion, the macrophage will die off, releasing certain cytokines and attracting further lung macrophages and fibrolastic cells to lay down fibrous tissue, which eventually forms a fibrous mass. The result is interstitial fibrosis. The fibrotic scar tissue causes alveolar walls to thicken, which reduces elasticity and gas diffusion, reducing oxygen transfer to the blood as well as the removal of carbon dioxide. Asbestosis presents as a restrictive lung disease. The total lung capacity (TLC) may be reduced through alveolar wall thickening. In the more severe cases, the drastic reduction in lung function due to the stiffening of the lungs and reduced TLC may induce right-sided heart failure (cor pulmonale). More than 50% of people affected with asbestosis develop plaques in the parietal pleura, in the space between the chest wall and lungs. Clinically, patients present with dry inspiratory crackles, clubbing of the fingers, and a diffuse fibrotic pattern in the lower lung lobes (where asbestosis is most prevalent). Treatment There is no curative treatment. Oxygen therapy at home is often necessary to relieve the shortness of breath. Supportive treatment of symptoms includes respiratory physiotherapy to remove secretions from the lungs by postural drainage, chest percussion, and vibration. Nebulized medications may be prescribed in order to dilute secretions. Nickel is a chemical element, with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. It is one of the four ferromagnetic elements at about room temperature. Its use has

3 been traced as far back as 3500 BC. The metal is corrosion-resistant, finding many uses in alloys, as a plating, in the manufacture of coins, magnets and common household utensils, as a catalyst for hydrogenation, and in a variety of other applications. Enzymes of certain life-forms contain nickel as an active center making the metal essential for them. Toxicity Exposure to nickel metal and soluble compounds should not exceed 0.05 mg/cm³ in nickel equivalents per 40-hour work week. Nickel sulfide fume and dust is believed to be carcinogenic, and various other nickel compounds may be as well. Nickel carbonyl, [Ni(CO) 4 ], is an extremely toxic gas. The toxicity of metal carbonyls is a function of both the toxicity of a metal as well as the carbonyl's ability to give off highly toxic carbon monoxide gas, and this one is no exception. It is explosive in air. Sensitized individuals may show an allergy to nickel affecting their skin, also known as dermatitis. Nickel is an important cause of contact allergy, partly due to its use in jewelry intended for pierced ears. Nickel allergies affecting pierced ears are often marked by itchy, red skin. Many earrings are now made nickel-free due to this problem. Cadmium is a chemical element with the symbol Cd and atomic number 48. A relatively abundant, soft, bluish-white transition metal, cadmium is known to cause cancer and occurs with zinc ores. Cadmium is used largely in batteries and pigments, for example in plastic products. Characteristics Cadmium is a soft, malleable, ductile, toxic, bluish-white bivalent metal. It is similar in many respects to zinc but forms more complex compounds. Batteries

4 About three-quarters of all the cadmium used is in batteries, predominantly in rechargeable nickel-cadmium batteries. Nickelcadmium cells have a nominal cell potential of 1.2 V. The cell consists of a positive nickel hydroxide electrode and a negative cadmium electrode plate separated by an alkaline electrolyte (potassium hydroxide). More recent Nickel-metal hydride batteries reduce the use of Ni-Cd batteries. Most of the remaining quarter is used mainly for pigments, coatings and plating, and as stabilizers for plastics. Other uses include: In paint pigments: Cadmium forms various salts, with CdS being the most common. This sulfide is used as a yellow pigment. Cadmium selenide can be used as red pigment, commonly called cadmium red. To painters that work with the pigment, cadmium yellows, oranges, and reds are the most potent colors to use. In fact, during production, these colors are significantly toned down before they are ground with oils and binders, or blended into watercolors, gouaches, acrylics, and other paint and pigment formulations. These pigments are toxic, and it is recommended to use a barrier cream on the hands to prevent absorption through the skin when working with them. Cadmium blue, green, and violet do not exist.. Toxicity Cadmium poisoning is an occupational hazard associated with industrial processes such as metal plating and the production of nickel-cadmium batteries, pigments, plastics, and other synthetics. The primary route of exposure in industrial settings is inhalation. Inhalation of cadmiumcontaining fumes can result initially in metal fume fever but may progress to chemical pneumonitis, pulmonary edema, and death. Cadmium is also a potential environmental hazard. Human exposures to environmental cadmium are primarily the result of the burning of fossil fuels and municipal wastes. Cadmium and several cadmium-containing compounds are known carcinogens and can induce many types of cancer.

5 Current research has found that cadmium toxicity may be carried into the body by zinc binding proteins; in particular, proteins that contain zinc finger protein structures. Zinc and cadmium are in the same group on the periodic table, contain the same common oxidation state (+2), and when ionized are almost the same size. Due to these similarities, cadmium can replace zinc in many biological systems, in particular, systems that contain softer ligands such as sulfur. Cadmium can bind up to ten times more strongly than zinc in certain biological systems, and is notoriously difficult to remove. In addition, cadmium can replace magnesium and calcium in certain biological systems, although these replacements are rare. Tobacco smoking is the most important single source of cadmium exposure in the general population. It has been estimated that about 10% of the cadmium content of a cigarette is inhaled through smoking. The absorption of cadmium from the lungs is much more effective than that from the gut, and as much as 50% of the cadmium inhaled via cigarette smoke may be absorbed. On average, smokers have 4-5 times higher blood cadmium concentrations and 2-3 times higher kidney cadmium concentrations than non-smokers. Despite the high cadmium content in cigarette smoke, there seems to be little exposure to cadmium from passive smoking. No significant effect on blood cadmium concentrations could be detected in children exposed to environmental tobacco smoke.