The P.E.L. for benzene exposure is ___ ppm in an 8hour period or ___ ppm in 15 minutes max.

The P.E.L. for benzene exposure is ___ ppm in an 8hour period or ___ ppm in 15 minutes max.

• A. 1 and 5
• B. 1 and 15
• C. 2 and 8
• D. 5 and 25

Answer: (A)

The main idea is that benzene has defined safety limits for both long-term and short-term exposure. The Permissible Exposure Limit uses an 8-hour time-weighted average (TWA) and a 15-minute short-term exposure limit (STEL). For benzene, these values are 1 ppm averaged over 8 hours and 5 ppm allowed for any 15-minute period. That’s why the correct pairing is 1 ppm for 8 hours and 5 ppm for 15 minutes. This reflects benzene’s high toxicity and carcinogenic risk: it’s controlled so daily exposure stays low, while brief spikes are limited to a higher short-term ceiling to prevent acute effects, but not so high as to pose long-term risk. The other options propose different numbers that don’t match the standard 8-hour TWA and 15-minute STEL values used for benzene, so they aren’t correct.

The main idea is that benzene has defined safety limits for both long-term and short-term exposure. The Permissible Exposure Limit uses an 8-hour time-weighted average (TWA) and a 15-minute short-term exposure limit (STEL). For benzene, these values are 1 ppm averaged over 8 hours and 5 ppm allowed for any 15-minute period. That’s why the correct pairing is 1 ppm for 8 hours and 5 ppm for 15 minutes.

This reflects benzene’s high toxicity and carcinogenic risk: it’s controlled so daily exposure stays low, while brief spikes are limited to a higher short-term ceiling to prevent acute effects, but not so high as to pose long-term risk. The other options propose different numbers that don’t match the standard 8-hour TWA and 15-minute STEL values used for benzene, so they aren’t correct.