Reference Dose Utilization Ratio

What is this formula?

The Reference Dose Utilization Ratio (RUR) expresses exposure as a percentage of the Reference Dose (RfD). It indicates how much of the allowable daily exposure is being utilized.

When to use it

Use this formula when communicating risk assessment results to regulators, managers, or the general public, as percentages are often easier to interpret than Hazard Quotient values.

Example

An individual has an estimated exposure of 0.008 mg/kg/day. The reference dose is 0.020 mg/kg/day.

Data:

E = 0.008 mg/kg/day

RfD = 0.020 mg/kg/day

Formula:

RUR = (E / RfD) × 100

Substitution:

RUR = (0.008 / 0.020) × 100

Result:

RUR = 40%

Interpretation:

The estimated exposure uses 40% of the available reference dose.

Applications

- Human health risk assessment

- Environmental monitoring

- Regulatory reporting

- Chemical exposure management

- Public health communication

Note

The Reference Dose Utilization Ratio is a derived risk communication metric based on the Hazard Quotient concept. Values below 100% indicate exposure below the reference dose, while values above 100% indicate that exposure exceeds the reference level. Different agencies may use different reference doses for the same substance.