A low-cost radioactive scan is first done to determine if the level of radioactivity is high enough to progress to further analyses. The level of radioactivity that would call for further analysis is normally the ______ for ______ or _________ but can be varied by the particular state drinking water agency.

A low-cost radioactive scan is first done to determine if the level of radioactivity is high enough to progress to further analyses. The level of radioactivity that would call for further analysis is normally the ______ for ______ or _________ but can be varied by the particular state drinking water agency.

• A. MCL, uranium, thorium
• B. detection limit, gross alpha, gross beta emitters
• C. MCL, roentgen equivalent man (rem), radiation adsorption dose (rad)
• D. detection limit, uranium, thorium

Answer: (B)

The idea being tested is how screening for radioactivity in drinking water is typically triggered. In a low-cost initial scan, you look for any sign of alpha or beta radiation. The threshold used to decide if you should do more detailed testing is the detection limit for gross alpha or gross beta emitters. If the gross measurements are at or above that detection limit, labs proceed with more specific analyses to identify exact radionuclides and assess compliance. Different states may set the exact threshold, but the screening step is always based on these broad, low-cost detection limits. Why this fits best: gross alpha and gross beta tests are quick, inexpensive screens designed to flag potential contamination without pinpointing exact isotopes. Using a detection limit as the trigger ensures that everything below it is considered not actionable for further testing, while anything at or above prompts more thorough, isotope-specific analyses. The other options are less fitting because they mix regulatory limits (MCL) or dose units (rem, rad) with screening decisions, or focus on specific isotopes (uranium, thorium). The standard first-pass screening relies on the broad detection limits for gross alpha and gross beta emitters, not regulatory limits or dose measurements.

The idea being tested is how screening for radioactivity in drinking water is typically triggered. In a low-cost initial scan, you look for any sign of alpha or beta radiation. The threshold used to decide if you should do more detailed testing is the detection limit for gross alpha or gross beta emitters. If the gross measurements are at or above that detection limit, labs proceed with more specific analyses to identify exact radionuclides and assess compliance. Different states may set the exact threshold, but the screening step is always based on these broad, low-cost detection limits.

Why this fits best: gross alpha and gross beta tests are quick, inexpensive screens designed to flag potential contamination without pinpointing exact isotopes. Using a detection limit as the trigger ensures that everything below it is considered not actionable for further testing, while anything at or above prompts more thorough, isotope-specific analyses.

The other options are less fitting because they mix regulatory limits (MCL) or dose units (rem, rad) with screening decisions, or focus on specific isotopes (uranium, thorium). The standard first-pass screening relies on the broad detection limits for gross alpha and gross beta emitters, not regulatory limits or dose measurements.