MassEnviroScreen Cumulative Impact Score - A Supplement for Environmental Justice Prioritization

Introduction and purpose

This document presents a tool for identifying or prioritizing the most environmentally vulnerable or burdened communities in Massachusetts based on a cumulative impact score that incorporates exposure to pollution and climate risks and the presence of sensitive or vulnerable populations, as well as whether the community meets criteria related to limited English proficiency, household income, or presence of tribal land. It is intended to act as a supplement to the Massachusetts Environmental Justice Population definition.

This tool - MassEnviroScreen - is a hybrid approach that utilizes elements of the current Massachusetts Environmental Justice Population definition, the presence of federally recognized tribal lands, and a cumulative impact mapping approach. The cumulative impacts mapping approach is modeled on those used by California EPA’s CalEnviroScreen tool and the Colorado EnviroScreen tool. The California and Colorado tools utilize a ‘cumulative impact score’ to describe the relative environmental burden of communities across the state and to prioritize those that are most burdened. California defines cumulative impacts as “the exposures, public health or environmental effects from the combined emissions and discharges, in a geographic area, including environmental pollution from all sources, whether single or multi-media, routinely, accidentally, or otherwise released.” Impacts consider “sensitive populations and socio-economic factors, where applicable and to the extent data are available.” The Colorado tool augments the CalEnviroScreen approach by adding climate risks, which is the approach followed here.

A ‘cumulative impact score’ is a numerical value that ranks every community (i.e., census block group) on a scale from 0 to 100. Higher values indicate greater cumulative burden. These values also represent percentile ranks, which means that a community’s score also indicates the percentage of scores in a group that are equal to or lower than a given score. For example, a census block group with a score of 50 (50th percentile) means that its cumulative impact score is equal to or higher than 50% of census block groups in the state. In this model, we follow California’s example of using a score of 75 (the 75th percentile) as one of the thresholds for identifying the most impacted or ‘Unfairly Burdened Areas.’ Census block groups with a minimum score of 75 experience cumulative impacts that are equal to or higher than 75% of block groups in the state. In other words, these block group represent the top 25% of cumulative impact scores in Massachusetts.

To define “Unfairly Burdened Areas” in this tool, cumulative impact scores of 75 or higher are combined with two of the existing Massachusetts EJ criteria - limited English speaking households and low income - as well as the presence of federally-recognized tribal territory.

Unfairly Burdened Areas are communities (i.e., census block groups) that meet one or more of the following criteria:
  • cumulative impact score (i.e, MassEnviroScore) of 75 or greater, OR
  • annual median household income is 65 percent or less of the statewide annual median household income, OR
  • 25 percent or more of households identify as speaking English less than “very well,” OR
  • occupy or intersect land within the boundaries of Federally Recognized Tribes, OR
  • health or air quality indicators exceed 200% of the statewide average

Figure 1 is an interactive map that displays ‘Unfairly Burdened Areas’ (census block groups in red), as defined above. Click on a block group to see its MassEnviroScreen score and the subscores (described in more detail later in the document) that comprise that cumulative burden, as well as other details. Text in red indicates a criterion’s threshold is exceeded or met. Text in blue indicates a criterion’s threshold is not exceeded or met. Select the checkbox next to ‘MA EJ Populations’ (upper right corner) to compare these Unfairly Burdened Areas with block groups identified as Environmental Justice Populations under Massachusetts law. Finally, activate the ‘MassEnviroScore’ radio button to see cumulative impact scores for every census block group across the state.

Figure 1

MassEnviroScreen scoring methodology

The MassEnviroScreen cumulative impact score model is based on three components representing Pollution and Climate Burden – Exposures and Environmental Effects and Climate Risks – and two components representing Population Characteristics – Sensitive Populations (e.g., in terms of health status and age) and Socioeconomic Factors.

Model characteristics

The model:

  • Uses 30 statewide indicators to characterize both Pollution and Climate Burden and Population Characteristics
  • Uses percentiles to assign scores for each of the indicators in a given geographic area. The percentile represents a relative score for the indicators.
  • Uses a scoring system in which the percentiles are averaged for the set of indicators in each of the four components (Exposures, Environmental Effects, Climate Risks, Sensitive Populations, and Socioeconomic Factors).
  • Combines the component scores to produce a MassEnviroScreen score for a given place relative to other places in the state, using the formula below.

Formula for calculating MassEnviroScreen Score

After the components are scored within Pollution Burden and Climate Risk or Population Characteristics, the scores are combined as follows to calculate the overall MassEnviroScreen Score:

ALT * The Environmental Effects and Climate Risks scores were weighted half as much as the Exposures score.

Scores for the pollution burden and climate risk and population characteristics categories are multiplied (rather than added, for example). This multiplication approach is based on research which shows that socioeconomic and health/sensitivity factors are “effect modifiers” that multiply the risks posed by pollutants and climate risks. Various environmental health and emergency response organizations use a similar scoring system: Risk = Threat x Vulnerability.

Within the MassEnviroScreen score map, clicking on individual census block groups shows both the final MassEnviroScreen score as well as the Pollution and Climate Burden and the Sensitive Pop SubScores. The Pollution and Climate Burden Subscore represents the percentile rank (0 - 100) of the block group for averaged pollution burden and climate risk component indicators. Similarly, the Sensitive Pop SubScore represents the percentile rank (0 - 100) of the block group for averaged population characteristics component indicators.

Model indicators

The MassEnviroScreen score model is computed from 30 statewide environmental, socioeconomic, and health indicators. These indicators are listed in Table 1 below. Details and data sources for model indicators can be found in the MassEnviroScreen Documentation.

Table 1: MassEnviroScreen Score Indicators
Pollution and Climate Burden
Population Characteristics
Environmental Exposures Environmental Effects Climate Risks Sensitive Populations Socioeconomic Factors
PM2.5 Pollution Cleanup Sites Drought Pediatric Asthma Adults without a High School degree
Ozone Groundwater Threats Wildfire Risk Low Birth Weight Infants Housing Burdened Low Income Households
Nitrogen dioxide (NO2) Hazardous Waste Generators and Facilities Flood Risk Elevated Blood Lead Levels in Children Linguistically Isolated Households
Diesel Particulate Matter Solid Waste Sites and Facilities Extreme Heat Days Premature Mortality Poverty
Drinking Water Non-compliance Impaired Water Bodies Adult High Blood Pressure Unemployment
Air Toxics Cancer Risk Coronary Heart Disease
Respiratory Hazard Index Chronic Obstructive Pulmonary Disease
Proximity to Heavy Traffic Adult Cancer

Comparison with Massachusetts Environmental Justice Populations

There are several key differences between the MassEnviroScreen model approach and the Massachusetts Environmental Justice Population definition:

  • The MA EJ Population definition is based entirely on three demographic criteria - percent minority OR percent limited English speaking households, OR percent households below 65% of statewide median household income.
  • MassEnviroScreen defines “Unfairly Burdened Areas” based on a cumulative impact score that integrates demographic criteria, health status, and environmental conditions across more than two dozen indicators, OR percent of limited English speaking households, OR percent of households below 65% of statewide median household income, OR presence of federally recognized tribal land.
  • MassEnviroScreen does not use race or ethnicity as indicators.

Both approaches, however, are based on important decisions about which indicators to use, and what threshold to use for prioritization. The latter are important policy decisions that may not be resolved by a technical analysis.

Coverage of the state

Under the current Massachusetts Environmental Justice Population definition 51.7% of Massachusetts block groups are classified as environmental justice communities. These environmental justice block groups occur in 209 (59.5%) of Massachusetts municipalities (based on American Community Survey 2023 5-year estimates). By contrast, 37.4% of Massachusetts block groups meet the criteria for MassEnviroScreen’s Unfairly Burdened Areas. The latter occur in 171 (48.7%) of Massachusetts municipalities. A breakdown of the number and percentage of census block groups meeting the various criteria that define a an Unfairly Burdened Area are displayed in Table 2. Note that percentages do not total to 100% because block groups may meet multiple criteria.

Table 2: Criteria for Unfairly Burdened Areas
UBA Criteria Number of Block Groups Pct of UBAs Pct of State Block Groups
MassEnviroScreen Score > 75%tile 1279 64.5% 25%
Median Household Income < 65% MA 838 42.2% 16.4%
Limited English Households > 25% 321 16.2% 6.3%
Coronary Heart Disease > 200% MA 253 12.8% 5%
Premature Mortality > 200% MA 191 9.6% 3.7%
Low Birthweight > 200% MA 167 8.4% 3.3%
Elevated Blood Lead Levels > 200% MA 167 8.4% 3.3%
Pediatric Asthma > 200% MA 109 5.5% 2.1%
Tribal Territory 9 0.5% 0.2%
Ozone > 200% MA 0 0% 0%
PM25 > 200% MA 0 0% 0%

Overlap with EJ criteria

Although MassEnviroScreen identifies a smaller number of census block groups, there is considerable overlap between communities meeting the state’s current environmental justice population definition and the criteria for Unfairly Burdened Areas. Although 37.4% of census block groups in the state meet the criteria for Unfairly Burdened Areas, 61.5% of block groups defined as environmental justice populations also meet the Unfairly Burdened Areas criteria. Figure 2 shows the degree of overlap between the various criteria of environmental justice populations and Unfairly Burdened Areas. There is 100% overlap with all state Environmental Justice Population criteria save for the Minority-only category. Only 38% of census block groups defined as a Environmental Justice Population based solely on the Minority criterion (i.e., 40% or more minority) overlap with Unfairly Burdened Areas as defined here.

Figure 2

MassEnviroScreen cumulative impact scores by EJ criteria

Figure 3 shows the distribution of MassEnviroScreen cumulative impact scores for block groups meeting each of the environmental justice criteria. In comparison to non-EJ block groups in Massachusetts, median cumulative impact scores for six out of the seven EJ criteria are above the 50th percentile. In other words, most block groups meeting the state’s current environmental justice population definition have cumulative impact scores that are higher than 50% of block groups across the state overall. In addition, five out of the seven also have median values above the 75th percentile or threshold for Unfairly Burdened Areas.

Figure 3

Next Steps?

This report is a draft product for discussion.

Questions about this report should be directed to:

Marcos Luna, PhD Professor, Geography and Sustainability Department Salem State University Salem, MA mluna at salemstate.edu