Preventing Chemical Accidents: Understanding MSDS’s & Assessing Chemical Hazards
Section II: Hazardous Ingredients (continued)
LD50 or LC50 (Lethal Dose and Lethal Concentration): These terms refer
to the dose or concentration of a chemical, which, in experiments, kills 50 percent of the test animals.
Skin or “S”: This means the substance may be absorbed through the skin by liquid contact or through the mucous membranes and eyes by direct contact or airborne contact.
Below are some explanations for the numbers used in this section. (Note that for most substances, mg/m3 can be converted into ppm, which means parts per million. It is used for measuring the concentration of a gas or vapor in a million parts of air.)
• mg/m3: This is milligrams of substance per cubic meter of air. The term is most commonly used for measuring concentrations of dusts, metal fumes, or other particles in the air.
• mg/kg: This is milligrams of substance per kilogram of body weight. It is used generally to measure toxic chemicals given to experimental animals to ingest.
Section III: Physical/Chemical Characteristics
This section provides critical information about the properties of chemicals such as vapor pressure, vapor density, boiling point and evaporation rate. These measurements can help you learn a lot about hazards of a particular chemical.