Appendix A. Common Safety Symbols
Appendix B. National Fire Protection Association Hazard Labels
Appendix C. Substances with Greater Hazardous Nature Than Educational Utility
Appendix D. Substances with a Hazardous Nature, But May Have Potential Educational Utility .
Appendix E. Incompatible Chemicals
Appendix F. Recommended Safety and Emergency Equipment for the Laboratory
Appendix H. What are Exposure Limits?
Appendix I. General Guidelines to Follow in the Event of a Chemical Accident or Spill
Appendix J. Understanding an MSDS
Appendix K. Sample MSDS
Appendix L. Web Site Resources
Appendix M. Glossary

Appendix G. How Does a Chemical Enter the Body?

• A chemical can enter the body through different routes.
• These different routes of exposure and the types of exposure (acute or chronic) can affect the toxicity of the chemical.
• The most probable (primary) route(s) of exposure to a chemical will be identified in the MSDS.
• Three principal routes of exposure include: dermal exposure (skin), inhalation, and ingestion (oral).

Dermal Exposure

Although the skin is an effective barrier for many chemicals, it is a common route of exposure. The toxicity of a chemical depends on the degree of absorption that occurs once it penetrates the skin. Once the skin is penetrated, the chemical enters the blood stream and is carried to all parts of the body. Chemicals are absorbed much more readily through injured, chapped, or cracked skin, or needle sticks than through intact skin. Generally, organic chemicals are much more likely to penetrate the skin than inorganic chemicals.

Dermal exposure to various substances can also cause irritation and damage to the skin and/or eyes. Depending on the substance and length of exposure, effects of dermal exposures can range from mild temporary discomfort to permanent damage.

Inhalation

Inhalation is another route of chemical exposure. Chemicals in the form of gases, vapors, mists, fumes, and dusts entering through the nose or mouth can be absorbed through the mucous membranes of the nose, trachea, bronchi, and lungs. Unlike the skin, lung tissue is not a very protective barrier against the access of chemicals into the body. Chemicals, especially organic chemicals, enter into the blood stream quickly. Chemicals can also damage the lung surface.

Ingestion

Ingestion involves chemicals entering the body through the mouth. Chemical dusts, particles and mists may be inhaled through the mouth and swallowed.

They may also enter through contaminated objects, such as hands or food that come in contact with the mouth. Absorption of the chemicals into the bloodstream can occur anywhere along the length of the gastrointestinal (GI) tract.