91Â鶹¾«Æ·

The Honorable Lee M. Zeldin Administrator, U.S. Environmental Protection Agency EPA Docket Center OAR Docket, Mail Code 28221T 1200 Pennsyvania Ave NW Washington, D.C. 20460

Docket ID No. EPA-HQ-OAR-2025-0194—Reconsideration of 2009 Endangerment Finding and Greenhouse Gas Vehicle Standards

Dear Administrator Zeldin,

On behalf of the more than 37,000 members of the American Society for Microbiology (ASM), thank you for the opportunity to respond to this proposed rule. 91Â鶹¾«Æ·is one of the oldest and largest life science societies with members in the U.S. and around the world. Our mission is to promote and advance the microbial sciences.

91Â鶹¾«Æ·urges the EPA to consider the body of scientific evidence showing the impacts of increased CO2 emissions and associated increases in temperature, humidity, precipitation and extreme weather events on microbial life and the adverse impacts of these changes to human health and welfare. 91Â鶹¾«Æ·urges the EPA to uphold the 2009 endangerment finding and continue to regulate greenhouse gas emissions due to the threat that greenhouse gas emissions pose to public health and welfare.

As the most abundant organisms on Earth, microorganisms make considerable contributions to climate systems and are greatly affected by a changing climate. Microbiologists have long studied and documented the profound impact of climate on microbes, public health and food production. Increased greenhouse gas emissions, including CO2, CH4 and N2O, have well-documented direct impacts on microbial life—evidence suggests that activating CO2 pathways leads to increased virulence of fungal and bacterial pathogens () and increased CO2 concentrations in water and air promote the rapid growth of algae, leading to harmful algal blooms ().

Since 2021, the American Academy of Microbiology, ASM’s honorific leadership group and think tank, has been undertaking a scientific portfolio on the topic of microbes and climate change. As part of this scientific portfolio, the Academy released a report in 2022 outlining how climate change impacts microbial life and how those changes negatively affect society. This evidence supports the 2009 endangerment finding. The report notes the following:

• Shifts in temperature, precipitation, humidity, CO2 concentrations and nutrient availability driven by climate change can increase water- and food-borne infections.
• Climate change will increase the cost and burden of infectious diseases on the global population. For example, the risk of zoonotic diseases will increase as humans are forced to migrate to new environments. 
• The transmission of airborne respiratory pathogens, such as influenza virus or SARS-CoV-2, is influenced by humidity levels, which can be impacted by climate change (; ).
• Climate change-induced warming and severe storms will expand the geographical and temporal range of plant pathogens, decreasing crop yield and quality.
• Higher temperatures are associated with increased levels of waterborne pathogens and cases of diarrheal disease (; ). Warmer waters also increase the risk of viruses and parasitic diseases in natural and managed ecosystems, including those that support marine fisheries. 
• Microorganisms' impact on urban environments is also influenced by climate change. Warmer temperatures accelerate microbial corrosion of civil infrastructure and climate change-driven weather events impact indoor microbial communities. For example, flooded homes increase exposure to mold and other allergens (; ; ; ).

Another Academy report, in partnership with the American Geophysical Union, about water, waterborne pathogens and public health, finds that as water becomes scarcer and more polluted, the risk of waterborne diseases increases, causing increased illness and death in the U.S. and globally. Annually, waterborne diseases in the U.S. result in approximately 7.2 million illnesses and 6,630 deaths, a direct health care cost estimated at 3.3 billion USD per year (). Wastewater infrastructure, which is essential to preventing the spread of waterborne diseases, is vulnerable to damage from extreme weather events associated with climate change.

Microbes can be a part of climate change solutions, from developing sustainable biofuels and bioproducts using microbes to capturing greenhouse gases with biofilters. 91Â鶹¾«Æ·and the International Union for Microbiological Societies published a report providing a comprehensive framework for assessing and implementing strategies that will mitigate climate change. The American Academy of Microbiology has also studied the role of microbes in mediating methane emissions and published a research roadmap for mitigating methane emissions from landfills and agricultural systems. 

91Â鶹¾«Æ·urges the EPA to take the body of scientific evidence documenting the impacts of climate change on microbes, public health and agriculture into account while developing climate regulations. 91Â鶹¾«Æ·and its members stand ready to assist the EPA in developing and implementing microbial climate change solutions to address the threat of greenhouse gas emissions to public health and welfare. Please contact Nicole Zimmerman, Senior Federal Affairs Officer, at nzimmerman@asmusa.org for further information or to arrange a conversation about microbes and climate.

Thank you,

Jay T. Lennon, Ph.D.
Chair, 91Â鶹¾«Æ·Applied and Environmental Microbiology Scientific Unit

Margie Lee, DVM, M.S., Ph.D.
Chair, 91Â鶹¾«Æ·Public and Scientific Affairs Committee