Pesticide Impact Index

Project Description

Municipalities with IPM ordinances need a way to track progress in reducing pesticide impact over time. The metric chosen must be easy to use and understand. Ideally, it should be:

  • Representative of actual impacts on human health and the environment
  • Usable even with limited data
  • Transparent and easy to understand

One option is to assign a rating to each pesticide product used. Other systems exist for agricultural use products (Pesticide Risk Mitigation Engine and Environmental Impact Quotient), but there is a dearth of options for urban and suburban IPM.

We leveraged Pesticide Research Institute’s pesticide databases and the San Francisco Hazard Tier Rating system to create the Pesticide Impact Index (PII) for the City of San Francisco.

PII Components   PII_EIQ components






Advantages of PII over EIQ

The Environmental Impact Quotient (EIQ) is a common index used to assess impact and track impact over time. Pesticide Impact Index:

  • Is product-specific, rather than active ingredient-based
  • Encompasses indoor-use products and other non-agricultural-use products
  • Accounts for low toxicity products
  • Is easily reproducible; inputs are publicly available
  • Produces similar results with agricultural-use herbicides

Comparison with Risk Assessments PII_USFS RA Components

The best possible estimate of impact comes from quantitative risk assessments, because they provide accurate estimates of actual exposure. The risk assessments featured were developed by the US Forest Service.

This set of risk assessments is more accurate than EIQ and PII when ranking relative impacts associated with Savana and Roundup Ultra Herbicide.

An index based on scores and summed across criteria (environmental impacts, human health impacts) may fail to capture large differences in relative risk. A score of 3 is not very different from a score of 1 in an index that sums 4 scores. We trade accuracy for administrative simplicity.

When should I use PII and when should I use EIQ to assess impact?

  • Tracking pesticide use over time
  • Urban settings
  • Include the effects of “inert” ingredients
  • Pesticide product use in pounds is available
  • Comparing specific pesticide products in known conditions
  • Agricultural use
  • Pesticide chemical use in pounds per acre is available

Impact Index in Action

The Impact Index is calculated for each pesticide application, and then summed over the year to create a representation of the change in impact over time.












These data show that San Francisco Recreation and Park Department is reducing pesticide use over time, and selecting lower toxicity products. This scenario can be compared with two hypothetical scenarios, below.

Sub toward less Sub Toward More Toxic








Contact PRI at to see how the Pesticide Impact Index can be used to track your pesticide impacts over time!