Routes of Exposure
A. Dermal Contact
Skin contact is one of the most common chemical exposure routes in laboratory settings. Spills and splashes can result in overt skin contamination. In addition, laboratory personnel may unknowingly contaminate themselves when they touch work surfaces, glassware, or equipment contaminated during experiments. A common result of skin contact is localized irritation or dermatitis. However, a number of materials are absorbed through the skin to produce systemic poisoning. The main portals of entry for chemicals through the skin are the hair follicles, sebaceous glands, sweat glands, and cuts or abrasions of the outer layers of the skin. The follicles and the glands contain blood vessels, which facilitate the absorption of chemicals into the body. Chemicals can also enter the body when contaminated hands touch the mouth, nose, eyes, sores or cuts. For more information, refer to the glove use policy in Chapter 5: Protective Clothing and Equipment.
Inhalation of toxic vapors, mists, gases, or dusts can produce poisoning by absorption through the mucous membrane of the mouth, throat and lungs, and can seriously damage these tissues by local action. Inhaled gases or vapors may pass rapidly through the capillaries of the lungs and enter the circulatory system. The degree of injury from inhalation of toxic substances depends on the material’s toxicity, solubility in tissue fluids, concentration, and the duration of exposure.
Although inhalation hazards are more often associated with gases and volatile chemicals, both solids and non-volatile liquids can also present an inhalation hazard for laboratory personnel. Laboratory chemicals in the form of dusts and particulates can become airborne when transferred from one container to another. Grinding and crushing procedures can also produce aerosols. Splashes created from spills and vigorous shaking and mixing form aerosols. Many of these generated particulates do not settle out but remain suspended in the air and travel along air currents in the room. Some of these particulates can be inhaled and deposit in the respiratory tract. For many operations, you might not recognize that aerosols are present and a hazardous situation exists. All laboratory operations involving an open vessel will result in aerosol release. Such operations include weighing, stirring, pouring, pipetting, injections with a needle and syringe, handling animals, and removing caps and stoppers. As an alert laboratory person, take care not to create aerosols.
Ingestion of toxic materials in the laboratory can occur when contaminated hands come in contact with the mouth, or with food items. The laboratory environment can contaminate food items and utensils. Do not mouth pipette, as this can result in aspiration of toxic materials. For more information, refer to the laboratory food policy in Chapter 3: General Safety Principles and Practices.
Accidents involving needles and syringes can result in injection of toxic and/or infectious materials through the skin. Needles and syringes are among the most hazardous items used in the laboratory, especially when combined with the task of inoculating an uncooperative animal. Containers of toxic chemicals may break, resulting in hazard from contact with contaminated broken glass.
E. Ocular Exposure
The eyes are of particular concern, due to their sensitivity to irritants. Ocular exposure can occur via splash, or rubbing eyes with contaminated hands. Few substances are innocuous with eye contact, and several can cause burns and loss of vision. The eyes have many blood vessels, and rapidly absorb many chemicals. For more information, refer to the eye protection policy in Chapter 5.