Hazard Quotient
Compare an exposure dose with a caller-supplied route/time-compatible reference dose; HQ is a screening ratio, not a probability of harm.
Description
Divide a compatible daily exposure dose by a supplied reference dose and flag quotients strictly above one.
A reference dose, or RfD, is a noncancer risk-assessment benchmark incorporating a toxicological point of departure and uncertainty considerations. A hazard quotient compares an exposure estimate with that benchmark; it is a dimensionless screening ratio rather than a probability of harm.1
This tool calculates one exposure-to-reference ratio from values you supply. Both inputs use mg/kg/day and must also match in route, duration, chemical, and dose basis. Matching units alone does not establish a valid comparison.
The aboveUnitQuotient flag is true only when the quotient is strictly greater than one. A larger quotient indicates that the modeled exposure exceeds the supplied benchmark; it does not state how often adverse effects occur.
When to use Hazard Quotient
Use it to reproduce a single noncancer screening comparison after independently choosing an applicable reference dose and compatible exposure estimate.
How to use Hazard Quotient and interpret its calculation
- Enter a nonnegative exposureDoseMgPerKgDay for the relevant scenario.
- Enter a positive referenceDoseMgPerKgDay from a documented assessment, keeping the route and averaging assumptions compatible.
- Run the tool and read hazardQuotient and aboveUnitQuotient together. Record the source and applicability of the reference dose when reporting the ratio.
HQ = exposure dose / reference dose; above unit = HQ > 1 The common daily-dose units cancel. Equality does not set the flag.
The implementation performs the division and strict comparison. It does not look up chemical-specific reference values or sum multiple chemical or route quotients.
{
"input": {
"exposureDoseMgPerKgDay": 0.2,
"referenceDoseMgPerKgDay": 0.1
},
"output": {
"hazardQuotient": 2,
"aboveUnitQuotient": true
}
}| Exposure relation | Result |
|---|---|
| Exposure zero | HQ zero; flag false. |
| Exposure equals reference dose | HQ one; flag false. |
| Reference dose zero or negative | The input is rejected. |
Limitations and assumptions
No uncertainty analysis, mixture hazard index, exposure reconstruction, or clinical interpretation is performed. Neither a quotient above one nor below one independently proves the presence or absence of harm.
The reference dose is supplied rather than validated. An absorbed exposure estimate cannot automatically be compared with an administered-dose RfD without a justified basis adjustment.
Alternative or Complementary methods
A margin of exposure divides a point of departure by exposure, reversing the direction of the ratio and using a different benchmark. Deriving a candidate RfD from assessment factors is a separate task and does not establish an authoritative value.
References
-
Reference Dose (RfD): Description and Use in Health Risk Assessments — U.S. Environmental Protection Agency
Similar or alternative tools
- Margin of Exposure
Compare a point of departure with an exposure range using an inverse exposure ratio.
- NOAEL to RfD Converter
Apply supplied uncertainty factors and duration adjustment to derive a candidate reference dose.