We Are Underestimating the Health Harms of Climate Disasters

We Are Underestimating the Health Harms of Climate Disasters

As extreme weather becomes more common and catastrophic, we need new public health systems to better understand, prepare, and respond

Humacao, Puerto Rico, after Hurricane Maria devastated the island in 2017. Research suggests the true human and financial cost of the disaster may have been undercounted. Photo via AP Images/Andre Kang

The National Centers for Environmental Information (NCEI), which keeps track of severe weather events across the United States, has counted 378 billion-dollar disasters in the country since 1980. According to the NCEI, these highly destructive disasters, each with damages and costs topping $1 billion, have collectively taken 16,356 lives and cost $2.69 trillion. Continued climate change has led to disasters becoming both more frequent and more damaging: more than 100 of these disasters took place in the last five years (from 2019–2023), including 60 between 2020 and 2022. In 2023, there were 28 billion-dollar disasters in just one year.

Even these staggering numbers may be an undercount. Recent research highlights that the adverse, and uncounted, health impacts of disasters are much greater.

In assessing the human health impacts of a disaster, we typically focus on the number of deaths directly attributed to that disaster (i.e., the death toll). Yet, this number represents only the tip of the iceberg in terms of the adverse health impacts. Evidence shows that many disasters can impact our health for weeks, months, or even years after the initial event. A stark example of this was after Hurricane Maria swept across Puerto Rico in September 2017, devastating the island. The official death toll in December of that year was 64. Later studies, however, suggested that the mortality resulting from the hurricane was 70 times higher. The impacts on physical and mental health were surely far greater.

The NCEI approach to answering the important question—“What are the human and financial costs of extreme weather events and climate disasters?”—only tells part of the story. A full accounting of the total impacts of disasters must also consider the uncounted harms to human life. Comprehensively understanding the costs of disasters can effectively drive public health investments, policy priorities, and preparedness to avoid the worst outcomes.

Unfortunately, these uncounted harms are uniquely challenging to measure. The short-term and long-term health impacts of a disaster go far beyond the immediate death toll typically captured in official statistics. For example, someone may sustain an injury either during a severe storm or weeks later as they repair their damaged home. Similarly, mold in a water-damaged home takes time to grow and cause respiratory disease, and wildfire smoke may have effects lasting long after immediate exposure. Disasters may increase fatalities or illnesses even when those health effects are not easily attributable to the event: exposure to extreme heat can lead not only to heatstroke, but also to dehydration or kidney disease—conditions for which it’s harder to pinpoint the cause. 

In recently published research, our research group took a new step in quantifying the health impacts of billion-dollar disasters on US Medicare beneficiaries (mostly aged 65 years and older). Specifically, we assessed emergency department visits, nonelective hospitalizations, and deaths up to six weeks after disasters occurring between 2011 and 2016. We found that in the first week after an average-sized disaster, there were 268 excess emergency department visits and 20 excess deaths. Notably, the increase in mortality extends through the end of the study period of six weeks, long after the immediate death toll would typically be counted and reported. Finally, we found that the health harms were most pronounced in those communities that suffered the most severe economic losses and damages. In other words, the counties that bore the greatest economic destruction also had the greatest need for additional healthcare and suffered more deaths.

The incomplete assessment of the health impacts of disasters presents an important challenge for communities and governments working to build resilience to these increasing threats. Decisions regarding climate adaptation policies, including the just allocation of limited public health resources, should be based on a timely and accurate understanding of the impacts of disasters on specific communities. Similarly, healthcare systems in affected communities need timely and accurate information to fully prepare in advance of the next disaster. Equally important, public appreciation of the true dangers and costs of disasters is influenced by the available information—which, in turn, is an important driver of investment in public health resources and policy priorities for locally and nationally elected leaders.

Information on health impacts would, ideally, be available during or soon after an event so that we can optimally respond and prepare for the next disaster. But the true health impacts of devastating disasters typically take years to establish. 2023 was extremely hot across much of the US and the warmest year on record globally; yet we may not know for a year or more how many excess deaths or hospitalizations occurred because of the heat. 

Developing more comprehensive estimates of the health impacts of extreme weather events will require new systems, practices, and collaborations between public health agencies and the healthcare sector. New metrics will have to be defined, collected, and reported in a consistent and timely manner, with appropriate patient privacy protections. Analogous systems for tracking health outcomes already exist in the US. However, these systems are highly fragmented and compartmentalized, and there are currently only a few cities or states that have systems to track population health in near real time.

Creating or augmenting existing systems for this purpose at a national level will likely require substantial funding and government oversight, but the return on these investments is potentially very high. As extreme weather events become ever more common and costly, timely and comprehensive information on their adverse health impacts will help individuals, communities, healthcare providers, and other key stakeholders best prepare and reduce the suffering that follows. 

The primary goal of public health and health systems is to protect the well-being of people, especially those who are vulnerable to disasters. As we continue to mitigate and hopefully reverse the effects of anthropogenic climate change, we must also effectively measure and respond to the challenges our communities are facing today.

Gregory A. Wellenius is a Boston University School of Public Health professor of environmental health and director of the BU Center for Climate & Health.

Neil Singh Bedi is a rising fourth-year medical student at the BU Chobanian & Avedisian School of Medicine and a researcher at the BU School of Public Health.

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