Toxic effect of Xylene

(Muhammad usama, islamabad)

Xylene is an aromatic hydrocarbon widely used in industry and medical technology as a solvent. It is a colorless, sweet-smelling liquid or gas occurring naturally in petroleum, coal and wood tar, and is so named because it is found in crude wood spirit . It has a chemical formula of C6 H4 (CH 3)2 and is referred to as “dimethyl benzene” because it consists of a six-carbon ring to which two methyl groups are bound. It exists in three isomeric forms: ortho-, meta- and para-xylene.

Xylene is used as a solvent in the printing, rubber, paint and leather industries. It is found in small amounts in airplane fuel, gasoline and cigarette smoke. In dentistry, xylene is used in histological laboratories for tissue processing, staining and cover slipping and also in endodontic retreatment as a guttapercha solvent. Its high solvency factor allows maximum displacement of alcohol and renders the tissue transparent, enhancing paraffin infiltration. In staining procedures, its excellent dewaxing and clearing capabilities contribute to brilliantly stained slides.

Exposure to xylene can occur via inhalation, ingestion, eye or skin contact. It is primarily metabolized in the liver by oxidation of a methyl group and conjugation with glycine to yield methyl hippuric acid, which is excreted in the urine. Smaller amounts are eliminated unchanged in the exhaled air. There is a low potential for accumulation. Xylene causes health effects from both acute (<14 days) and also chronic (>365 days) exposure. The type and severity of health effects depends on several factors, including the amount of chemical you are exposed to and the length of time you are exposed for. Individuals also react differently to different levels of exposure

The main effect of inhaling xylene vapor is depression of the central nervous system, with symptoms such as headache, dizziness, nausea and vomiting. The effects listed below can begin to occur with exposure to air levels of about 100 ppm. They are reversible and become more noticeable and serious as the length of time of exposure increase
Irritation of the nose and throat can occur at approximately 200 ppm after 3–5 min. Accidental splash in the eye may damage the surface of the eye, which will heal within a few days

Exposure to xylene at levels of 200 ppm or greater can irritate the lungs, causing chest pain and shortness of breath. Extreme overexposure (e.g., in a confined space) can result in pulmonary edema, a potentially life-threatening condition in which the lungs fill with fluid. However, there is no evidence that repeated, low-level exposure has any long-term effects on the lung

At very high levels of exposure, xylene can injure the liver and kidneys, but this is extremely unlikely to happen without noticeable effects on the nervous system. Generally, such damage is reversible. Low-level occupational exposure does not affect the liver and the kidneys.

Preventive measure

Local exhaust ventilation
Proper protective equipment

Substitution means finding a substance that can perform the same function and which may lessen the hazard. Care should be taken not to introduce any new hazards when selecting a substitute for a hazardous material. After the hazardous effects of xylene became indisputable in the 1970s, many potential substitutes became available, some with as many if not more hazards. In general, these substitutes fall into four classes and are marketed under various tradenames. The chemical components are one of the following:

Limonene reagents
Aliphatic hydrocarbon mixtures
Aromatic hydrocarbon mixtures
Mineral oil mixtures

Efforts to reduce the health hazards in the histology laboratories should be made to create a safer working atmosphere by making the histopathology technicians more familiar with the health hazards of xylene, safety measures and emergency procedures. The hazards of xylene are well documented, but the substitutes are not so thoroughly evaluated. Most of the less-expensive alternatives to xylene do not have the same miscibility with alcohol, wax and resinous mountants, and nearly all are sold under trade names without any obvious disclosure of the chemicals of which they are composed. The assumption that they are safe just because the manufacturer says so is ill advised. It may not be comforting to get exposed on a daily basis to large volumes of a product of unknown chemical composition and largely untested health effects. Usage of proper personal protective equipment and a decent fume hood prevents the hazardous effects of xylene. In view of the established adverse effects of xylene, the Indian Association of Occupational Hygiene should make a law to safeguard the histopathology technicians against occupational hazards.

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29 Nov, 2017 Views: 309


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