Protecting Public Health Is Complicated. But Science Can Help, and the Time Is Now.

For a long time, public health protections that limit the harm of pollutants have been narrowly targeted, asking "Will this chemical from this source pose harm to people?" But that's not how pollution is actually experienced. When we breathe the air or drink the water, we're taking in any potential contaminants all at once-with effects that can combine or even compound. It's important to look at the bigger picture.

Earlier this year, environmental health advocates scored a big win when the EPA (Environmental Protection Agency) updated the ethylene oxide sterilizer rule requiring commercial sterilizers to significantly lower their emissions. Ethylene oxide is a carcinogen, and exposures were too high under previous requirements, and stronger rules were overdue. But the requirements in the rule were developed considering that one carcinogen from that one type of facility. It was a big step towards providing adequate health protections, but

Environmental regulations need to look at people, not just pollutants-and the way to get there is by assessing cumulative impacts.

Cumulative impact assessments look at health, environmental, and social factors (stressors and burdens) to help officials make better environmental decisions. These assessments don't just ask: what does this one chemical do in isolation? Instead, they ask: "how will these pollutants from a variety of sources impact people who are dealing with exposure to other pollutants, or existing health conditions, or limited access to health care?" It's complicated-but fortunately, there's science that can help us answer these questions, and it's time to put it to use.

There are methods to assess cumulative impacts-and how we develop and use these methods matters. We don't just want to identify a problem-we need to know how to evaluate it and create solutions, and that can be complex.

Recently, the National Environmental Justice Advisory Council presented their recommendations on cumulative impacts to the EPA. We know we need to consider cumulative impacts in environmental decision-making, and it's been a lengthy journey to get a cumulative impact approach to public health on the table. Overburdened communities cannot wait any longer.

The big question is how-and fortunately, we're not starting from zero. Methods exist, and this body of work is growing.

Incremental (step-by-step) approaches

In 2022, the EPA published an Environmental Justice Legal Tools document and a Cumulative Impacts Addendum. These documents describe how the EPA understands their legal authorities to assess and address cumulative impacts and environmental justice. According to these documents, there is already a lot of legal authority to do this work. However, since major US environmental laws are enacted to protect the air, water, and land separately (i.e. the Clean Air Act, the Clean Water Act, the Safe Drinking Water Act), as a result, EPA programs are often implemented narrowly, not holistically.

If we think about cumulative impacts as a series of components-for example, multiple chemicals, multiple sources of pollution and pathways of exposure (eating, drinking, breathing, e.g.), or inclusion of non-chemical stressors-nearly every one of these components is a legal consideration in at least one of the major US environmental laws. These components are also being assessed and used in regulatory decision-making by some government agencies at the local, state, or federal level.

For example, compliance demonstrations for the National Ambient Air Quality Standards (NAAQS) are based on multi-source analyses. Site assessments for the Comprehensive Environmental Response, Compensation, and Liability Act, or 'Superfund', include consideration of multiple exposure pathways and pollutants. These Superfund site assessments and the Toxic Substances Control Act also require consideration of "susceptible subpopulations"-those harmed by pollution more than their counterparts due to higher exposures, social adversity, or other conditions. For example, inclusion of a non-chemical stressor-higher daily temperatures-was considered in the scientific document used to support the ozone standard, since there is evidence that exposure to higher daily temperatures together with ozone exposure is associated with higher mortality.

So, incrementally, environmental protection is becoming more like real life, where exposures are not singular and isolated. But we cannot stop there. Overburdened communities are not being protected fast enough by these incremental approaches.

Reports informing decisions

Minnesota passed a cumulative impacts law in 2008 that implemented a method that required facilities to include a report on potential health impacts when applying for a permit. The law requires this report to include multiple stressors and burdens, with both numeric and narrative descriptions of pollution and health impacts. This process requires the facilities' reports to include a section for each health impact associated with the air pollutants they will emit. Thanks to this requirement, Minnesota found that companies actually reduced their planned air pollution level (in their permits) to decrease the size and complexity of the report. Though it was indirect, this was one way to reduce air pollution in overburdened communities through cumulative impact assessments, and it wouldn't have happened under the status quo. Similarly, a new cumulative impacts law enacted in Massachusetts requires a Cumulative Impacts Assessment Report that describes existing conditions, multiple air pollutant analyses, impacts to climate, and multiple sources of air pollution.

Spreadsheets to the rescue

The Massachusetts Department of Environmental Protection is implementing their cumulative impacts law using an approach that includes results in both a report and a spreadsheet. The spreadsheet looks at multiple air pollutants at a time and compares their potential combined impacts with a rule-based comparison value. Region 7 of the EPA developed a "Cumulative Health and Impacts Assessment" (CHIA) desktop tool for Resource Conservation and Recovery Act permits in Iowa, where EPA has direct implementation responsibilities. The tool has been tested on several types of Region 7 permits and beta-tested with other Regional EPA Offices: you can watch this video to learn more.

Mapping cumulative impacts

Cumulative impact assessments started as mapping tools with multiple types of data. Sometimes the data are integrated, e.g. added together, and sometimes they are layered on top of each other to see where stressors and burdens congregate. The California EnviroScreen mapping tool was one of the first such methods, and it supports comparisons of multiple environmental and health burdens, including a combined index. The state of California uses these combinations of indicators to identify "disadvantaged communities" and prioritizes funds such as the Greenhouse Gas Reduction Fund and the Sustainable Communities Planning Grants and Incentive Programs to benefit these communities that have historically been under-resourced.

More recently, New Jersey enacted their Environmental Justice regulation using cumulative impacts concepts, with a method that compares stressors and burdens in an area where a permit is being considered with another (less burdened) area. They compare these indicators one by one and can deny, limit, or condition a permit if the proposed activity considered in the permit will increase a stressor that is already higher than in a less burdened area.

The National Academies of Science, Engineering and Medicine recently released a report on development of these types of tools, and the indicators in them. It's a great resource!

Combining stories and numbers to capture cumulative impacts: our new paper

Another important source of information in a cumulative impact assessment is the lived experience and data from community members most impacted by an environmental decision. However, assessments within environmental protection have traditionally been quantitative, such as water or air pollution concentration measurements. We need more than that to capture the whole story-including, for example, how often community members swim in a nearby lake, observe blue smoke from a stack, or experience headaches and itchy eyes.

So, how does someone combine stories and numbers? This type of question falls squarely into the realm of scientific approaches called Mixed Methods. Dr. Sandra Whitehead, Dr. Benjamin Pauli and I recently published a paper looking into how scientists have pulled together people's experiences, opinions, and feedback with quantitative data like maps or pollution exposure estimates. Researchers use stories (qualitative data) to inform how and where a quantitative approach will be implemented, and in reverse, used quantitative approaches to determine where to gather community stories and data. Researchers have also integrated the two approaches into the same charts or including quotes from impacted people together with data showing increasing levels of environmental impacts.

Many of the laws requiring use of these methods to inform environmental permitting are very recent, so it's too early to quantify benefits to communities. However, the CalEnviroScreen mapping tool has been utilized by the state of California since 2013 to direct 25% of cap and trade funds into communities identified as disadvantaged, and prioritizes compliance and enforcement inspections into communities with more pollution sources. All these methods can be modified to develop additional cumulative impact assessments to inform better protections in overburdened communities.

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