What is the Best's Hazard Index? Clarifying Environmental and Insurance Risk

September 27, 2025 •

4 min read

According to the EPA, a Hazard Index can be used to assess health risks from chemical mixtures, such as PFAS in drinking water. This is crucial context when asking What is the best's hazard index?, as the term is often conflated with a similar-sounding but unrelated insurance industry metric. This article separates fact from fiction to provide a comprehensive explanation of both.

Quick Summary

The Hazard Index is an EPA metric for assessing non-cancer health risks from chemical mixtures like PFAS, where a value over 1.0 indicates potential health risk. It is distinct from the insurance industry’s Best’s Hazard Index, which evaluates business risk.

Key Points

Two Distinct Indices: The term 'Hazard Index' refers to two unrelated concepts: one for public health from the EPA and another for insurance risk from A.M. Best.
Environmental Health Index: The EPA uses a Hazard Index to assess potential non-cancer health risks from chemical mixtures, like PFAS in drinking water.
Insurance Risk Index: A.M. Best's Hazard Index is a proprietary tool used by insurance underwriters to gauge risk and liability for specific industries and insurance lines.
Critical Threshold: For the EPA's index, a value over 1.0 indicates a potential health risk from cumulative exposure to certain chemicals.
Industry Context: A.M. Best's index assigns a numeric value (1-9) to indicate a business's relative riskiness, which is used for underwriting purposes.
Avoid Confusion: It is vital not to conflate the environmental health metric with the business-risk insurance metric, as they serve different purposes and measure different things.

Understanding the Environmental Protection Agency's Hazard Index

The Environmental Protection Agency (EPA) uses a Hazard Index (HI) as a tool to assess the health risks associated with exposure to chemical mixtures, particularly those found in drinking water. This index is especially relevant for substances like Per- and Polyfluoroalkyl Substances (PFAS), a group of man-made chemicals that can have additive health effects even at low concentrations. The EPA established a Hazard Index maximum contaminant level (MCL) of 1 for certain PFAS chemicals, including PFHxS, PFNA, HFPO-DA, and PFBS.

How the EPA's Hazard Index is Calculated

The calculation for the EPA's HI is based on a sum of fractions for each chemical being evaluated. The formula involves comparing the measured concentration of each chemical in a sample to its Health-Based Water Concentration (HBWC), a level considered safe. The fractions are then added together to get the total Hazard Index.

Formula: HI = Sum of (Concentration of Chemical / Health-Based Water Concentration)
Threshold: If the HI is less than or equal to 1, adverse non-cancer health effects are not expected.
Risk: An HI greater than 1 suggests that potential non-cancer health effects may occur due to the combined exposure to the chemical mixture.

For example, to calculate the HI for the specific PFAS chemicals regulated, you would divide the detected concentration of each chemical by its respective HBWC and sum the results. The running annual average HI must be considered for compliance purposes.

Deciphering A.M. Best's Underwriting Hazard Index

In a completely separate context, the insurance company A.M. Best provides a proprietary metric called the Best's Hazard Index. This is an independent professional opinion on the relative degree of risk exposure for specific lines of insurance within a particular business or industry. It is not a metric for personal or public health.

How A.M. Best's Index is Determined

The index values are determined by a careful review of research for a given business type, considering the frequency and severity of potential hazards related to different lines of insurance. The resulting index quantifies the degree of liability and risk.

Low Hazard (1-3): Negligible to slight risk exposure. The chances of a significant loss are not a great concern.
Medium Hazard (4-6): Minor to significant risk exposure. There is a greater chance of loss based on the frequency and severity of hazards.
High Hazard (7-9): Substantial to extensive risk exposure. The chances of loss are quite high and warrant close scrutiny.

This index is a key component of a Best's Underwriting Report, which provides underwriters with information on industry-specific hazards and loss controls. It helps them make informed decisions about underwriting a company or policy. For instance, the report for a General Contractor might list Workers’ Compensation with a high hazard index due to risks like falls from heights, cuts, and equipment injuries.

The Crucial Distinction: Environmental Health vs. Insurance

Confusion arises because both the EPA and A.M. Best use the term "Hazard Index," but their applications, methodologies, and implications are vastly different. One directly concerns public health, while the other is a business-focused risk assessment tool for the insurance industry. Confusing the two could lead to serious misinterpretations.

A Comparative Look at the Hazard Indices


Feature	EPA Hazard Index (Environmental Health)	A.M. Best Hazard Index (Insurance)
Purpose	To assess potential non-cancer health risks from chemical mixtures.	To quantify the degree of risk and liability for various insurance lines in an industry.
Subject	Chemical mixtures, often in drinking water, affecting public health.	Business operations, industry practices, and potential for insurance losses.
Calculation	Sum of fractions comparing chemical concentrations to health-based values.	Based on expert review of industry-specific hazards, loss severity, and frequency.
Interpretation	A value > 1 suggests potential health risk to the public.	A value of 1-9 indicates relative riskiness for insurance purposes.
Example	Used to determine compliance with drinking water regulations for PFAS mixtures.	Used by underwriters to evaluate a general contractor’s risk for workers’ comp.

Implications for General Health and Safety

For a general health perspective, the EPA's Hazard Index is the relevant metric to follow. It provides tangible information about potential health risks from environmental exposures, allowing regulatory bodies to set standards and warn the public. Monitoring this index, especially regarding emerging contaminants like PFAS, is vital for public health. You can find more information on the EPA's efforts regarding PFAS and other contaminants through their official site: EPA's PFAS Information.

Conclusion

In summary, when asking What is the best's hazard index?, it is critical to distinguish between the two prominent applications of the term. The EPA's Hazard Index is a public health tool, used to evaluate environmental risks from chemical mixtures, while A.M. Best's index is a proprietary insurance metric for assessing business risk. Understanding the context and purpose of each index is key to correctly interpreting its meaning and relevance to either public health concerns or insurance industry evaluations.

Frequently Asked Questions

The EPA's Hazard Index is a tool used to assess the potential for non-cancer health effects from exposure to mixtures of chemicals. It is often applied to contaminants like PFAS found in drinking water.

It is calculated by adding up the individual hazard quotients for each chemical in a mixture. Each quotient is the ratio of the measured chemical concentration to its health-based reference dose.

A Hazard Index of 1 is a critical threshold. A value less than or equal to 1 suggests that adverse non-cancer health effects are not expected from exposure to the chemical mixture.

The Best's Hazard Index is a tool from the insurance company A.M. Best. It provides an assessment of the relative degree of risk exposure for different lines of insurance within a particular industry.

The index is presented on a scale from 1 (low) to 9 (high), reflecting the severity and frequency of potential hazards. Underwriters use this rating to evaluate the risk associated with a specific business or industry.

No, the Best's Hazard Index is not a personal health metric. It is a business-to-business tool for the insurance industry to assess risk related to different lines of coverage.

Failing to distinguish between the EPA's public health index and A.M. Best's insurance risk index can lead to significant confusion and misunderstanding. One relates to environmental contamination and public safety, while the other is a commercial risk assessment.