Scientific Investigations Report 2007–5106
U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2007–5106
Table 4. Interpretation of Benchmark Quotients in relation to potential human-health significance and implications for water-quality monitoring.
[Benchmark quotient: The ratio of a contaminant concentration or an appropriate concentration statistic indicative of long-term exposure to its MCL or HBSL. Abbreviations: ≤, less than or equal to; >, greater than; MCL, Maximum Contaminant Level; HBSL, Health-Based Screening Level; ≥, greater than or equal to]
| Benchmark Quotient for a contaminant in water | Interpretation |
|---|---|
| ≤1 | Adverse effects are unlikely to be caused by this contaminant alone, even if water with such a concentration were to be ingested over a lifetime. |
| >1 | The contaminant concentration is of potential human-health concern if water with such a concentration were to be ingested without treatment over a lifetime. Adverse human-health effects will not necessarily be caused by this contaminant because MCLs and HBSLs are conservative (protective); they incorporate safety factors to account for uncertainty in toxicity information. Additionally, water may be treated or blended, potentially reducing contaminant concentrations. |
| ≥0.1 | Contaminant may warrant additional monitoring to analyze trends in its occurrence and to provide an early indication of a contaminant concentration that approaches its benchmark. |
U.S. Department of the Interior |
U.S. Geological Survey
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