Enter the exposure dose and reference dose for each contaminant into the calculator to determine the Hazard Index. This calculator can also evaluate any of the variables given the others are known.

Hazard Index Formula

The following formula is used to calculate the Hazard Index. 

HI = ∑(EDi / RfDi)

Variables:

  • HI is the Hazard Index
  • EDi is the exposure dose for contaminant i (mg/kg/day)
  • RfDi is the reference dose for contaminant i (mg/kg/day)

To calculate the Hazard Index, divide the exposure dose for each contaminant by its reference dose. Sum up these values for all contaminants. If the Hazard Index is greater than 1, it indicates a potential for non-carcinogenic health effects.

What is a Hazard Index?

A Hazard Index (HI) is a tool used in environmental health risk assessment to measure the potential risk of non-carcinogenic health effects from exposure to multiple hazardous substances. It is calculated by adding up the hazard quotients of each substance, which are the ratios of the potential exposure to the substance over a specified period to the reference dose. An HI of less than 1 indicates that no adverse health effects are expected, while an HI greater than 1 suggests potential health risks.

How to Calculate Hazard Index?

The following steps outline how to calculate the Hazard Index using the given formula:

  1. First, determine the exposure dose for each contaminant (EDi) in milligrams per kilogram per day (mg/kg/day).
  2. Next, determine the reference dose for each contaminant (RfDi) in milligrams per kilogram per day (mg/kg/day).
  3. Next, calculate the ratio of each contaminant’s exposure dose to its reference dose (EDi / RfDi).
  4. Sum up all the ratios calculated in the previous step (∑(EDi / RfDi)).
  5. Finally, the sum obtained in the previous step is the Hazard Index (HI).

Example Problem:

Use the following variables as an example problem to test your knowledge:

exposure dose for contaminant 1 (ED1) = 0.5 mg/kg/day

reference dose for contaminant 1 (RfD1) = 0.1 mg/kg/day

exposure dose for contaminant 2 (ED2) = 0.3 mg/kg/day

reference dose for contaminant 2 (RfD2) = 0.2 mg/kg/day

exposure dose for contaminant 3 (ED3) = 0.2 mg/kg/day

reference dose for contaminant 3 (RfD3) = 0.3 mg/kg/day