The basic routes for a chemical to enter the body in a laboratory setting are: inhalation, skin and eye contact, ingestion, and injection. The prevention of entry by one of these routes can be accomplished by control mechanisms such as engineering controls, personal protective equipment, and administrative controls. Each route can be minimized by a variety of control measures depending on the hazard and operation.
Employing administrative controls is the most desirable method for controlling chemicals exposures and must be used whenever plausible. Administrative controls include but are not limited to:
E1. Inhalation
Inhalation of hazardous chemicals is the most common route of entry to the body in laboratory operations. The American Conference of Governmental Industrial Hygienists (ACGIH) produces annual lists of Threshold Limit Values (TLVs) and Short Term Exposure Limits (STELs) for common chemicals and biological agents used in the laboratory. These values are guides, not legal standards, and are defined as follows:
Most of the 1968 TLVs were adopted by OSHA as Permissible Exposure Levels (PELs). To avoid significant inhalation exposures and to limit exposure to concentrations below PEL values, there are a number of control measures that can be used. Substituting a less toxic or less volatile chemical is the most desirable measure. If substitution is not practical, ventilation will be used to reduce exposure. Dilution ventilation may be used to reduce exposure to nonhazardous nuisance vapor and odor. All hazardous chemicals should be used in a properly functioning chemical fume hood. For extremely toxic substances, such as those classified as poison inhalation hazards by the Department of Transportation, the use of closed systems such as a glove box may be required. See also Section F. on Ventilation.
If necessary, personal protective equipment will be worn to limit chemical exposures. Dust masks or half face air purifying respirators may be utilized to this end. Respirators will not be worn in laboratories without first meeting the requirements of the OSHA Respirator Standard (1910.134). The requirements include training on proper use, selection, cleaning, and storage of respirators as well as fit testing and medical testing and surveillance to ensure that the user is physically capable of wearing a respirator. See our Respiratory Protection Program for more information.
E2. Skin and Eye Contact
Contact with the skin is a frequent mode of chemical injury. To reduce the risk of chemicals entering the body via skin and eye contact or skin absorption, controls include substitution and ventilation as described above. If this doesn't control the exposure the next step is the wearing of personal protective equipment such as gloves, eye protection, lab coats, aprons, appropriate shoes, and special protective equipment as required by the specific hazard present. The laboratory supervisor should consult references to determine the proper protective material for the chemicals being used.
Administrative controls to reduce skin/eye contact exposure include:
E3. Ingestion.
Most of the chemicals used in the laboratory are toxic if they enter the body by ingestion. The relative toxicity of a chemical can be determined by its LD50, which is the quantity of material that in a single dose will cause the death of 50% of the test animals. It is usually expressed in grams or milligrams per kilograms of bodyweight.
Ingestion should not be a route of exposure in a laboratory setting. The best way to eliminate exposure by ingestion is to limit actual contact with all chemicals. Wear gloves and practice good hygiene measures. Food and drink will not be stored in areas where chemicals are being used or stored. Label all chemical containers, and replace worn or faded labels ASAP. Chemicals will not be tasted, and pipetting and siphoning of liquids will not be done by the mouth.
E4. Injection
Exposure to chemicals by injection seldom occurs in the chemical laboratory. However, it can inadvertently occur through injury from metal or glass contaminated with chemicals or when chemicals are handled in syringes. Attention to detail and adherence to general standard operating procedures will provide control against accidental injection exposure. Red boxes will be used to collect all used needles and syringes. Separate collection containers will be used to collect broken glass. Label the containers, "CAUTION - Broken Glass". See also our Laboratory Waste Management Procedures.
Upon request, the CHO will assist with exposure evaluations for any suspected exposures to substances used in the laboratory. Records of exposure evaluations and exposure monitoring will be maintained at the Environmental Health and Safety Office, SB-4 McGregory Hall.
Last modified: April 08, 1998