Even __________ compounds (high LD50) can be hazardous.

• A. Toxic
• B. Nonvolatile
• C. Volatile
• D. Nontoxic

Answer: (D)

Lethal dose 50 (LD50) is a measure of acute toxicity from a single exposure, so a high LD50 means the chemical is less likely to cause death in that kind of test. But hazard isn’t limited to acute lethality. A substance can be labeled non-toxic in terms of acute lethality and still pose risks through other routes or effects. It might irritate skin or eyes, provoke an allergic reaction, or cause health problems with repeated or chronic exposure. There are also environmental hazards to consider, such as harm to aquatic life or persistence in the environment. So even compounds described as non-toxic can be hazardous under certain exposures or conditions, which is why label information covers more than just acute toxicity.