Office of Research

Procedure A

GENERAL PROCEDURES AND PRECAUTIONS FOR WORKING WITH SUBSTANCES OF MODERATE CHRONIC OR HIGH ACUTE TOXICITY

Before beginning a laboratory operation, each worker is strongly advised to consult one of the standard compilations that list toxic properties of known substances and learn what is known about the substances that will be used. The precautions and procedures described below (termed Procedure A in this report) should be followed if any of the substances to be used in significant quantities is known to be moderately or highly toxic. (If any of the substances being used is known to be highly toxic, it is desirable that there be two people present in the area at all times). These procedures should also be followed if the toxicological properties of any of the substances being used or prepared are unknown. If any of the substances to be used or prepared are known to have high chronic toxicity (e.g., compounds of heavy metals and strong carcinogens), then the precautions and procedures described below should be supplemented with additional precautions (termed Procedure B, which follow Procedure A in this report) to aid in containing and, ultimately, destroying substances having high chronic toxicity.

The overall objective of Procedure A is to minimize exposure of the laboratory worker to toxic substances, by any route of exposure, by taking all reasonable precautions. Whenever a toxic substance is being transferred from one container to another or is being subjected to some chemical or physical manipulation. The following three precautions should always be followed:

1.    Protect the hands and forearms by wearing either gloves and a laboratory coat or suitable long gloves (gauntlets) and a lab apron to avoid contact of toxic material with the skin. Appropriate protective eyewear and face protection must be worn.

2.    Procedures involving volatile toxic substances and those involving solid or liquid toxic substances that may result in the generation of aerosols must be conducted in a hood or other suitable containment device.

3.    After working with toxic materials, wash the hands and arms immediately. Never eat, drink, smoke, chew gum, apply cosmetics, take medicine, or store food in areas where toxic substances are being used.

These standard precautions will provide laboratory workers with good protection from most toxic substances. In addition, records that include amounts of material used and names of workers involved should be kept as part of the laboratory notebook record of the experiment. To minimize hazards from accidental breakage of apparatus or spills of toxic substances in the hood, containers of such substances should be stored in pans or trays made of polyethylene or other chemically resistant material and apparatus should be mounted above trays of the same type of material. Alternatively, the working surface of the hood can be fitted with a removable liner of adsorbent plastic-backed paper. Such procedures will contain spilled toxic substances in a pan, tray, or adsorbent liner and greatly simplify subsequent cleanup and disposal. Vapors that are discharged from the apparatus should be trapped or condensed to avoid adding substantial amounts of toxic vapor to the hood exhaust air. Areas where toxic substances are being used and stored should have restricted access, and special warning signs should be posted if a special toxicity hazard exists.

The laboratory worker should be prepared for possible accidents or spills involving toxic substances. If a toxic substance contacts the skin, a safety shower should be used to drench the affected area for 15 minutes. Contaminated clothing and shoes should be thoroughly decontaminated or incinerated. See Appendix C for information on handling spills.