Ending Greenhouse Gas Rules Could Harm Air Quality, Health

The U.S. Environmental Protection Agency (EPA) is currently reconsidering a rule which has allowed the government to set standards for and regulate greenhouse gas emissions for the last almost 16 years.

The 2009 Greenhouse Gas Endangerment Finding officially determined that six different greenhouse gases pose a threat to public health: carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride. The endangerment finding is the legal basis that lets the EPA set emissions standards for new motor vehicles and engines. 

“Rescinding the endangerment finding will have both direct and indirect effects on air pollution levels, and it certainly will have major impacts on greenhouse gas emissions,” says Jeremy Sarnat, ScD, associate professor of environmental health at Emory University’s Rollins School of Public Health. 

Sarnat studies the health impacts of human exposure to air pollution at HERCULES Exposome Research Center, where he is deputy director. He also served as chair of EPA’s Clean Air Scientific Advisory Committee (CASAC) until all members were dismissed by the Trump administration earlier this year. Here, he offers insights into how air pollution affects health and the potential impacts of deregulation.

Why is the endangerment finding so important?

Since the Clean Air Act Amendments of 1970, a well-established regulatory framework has existed and has been enforced by the EPA including six ubiquitous urban air pollutants, commonly referred to as criteria pollutants. These are pollutants that were known to both affect human health and have ecological impacts. The endangerment finding held that emissions of six greenhouse gases are instrumental in forming the criteria pollutants. So, it was incumbent upon the EPA to regulate these six additional greenhouse gases in the way that they regulate the other criteria pollutants.

It was not necessarily saying that there were specific direct health impacts from exposure to these greenhouse gases. But because of the role they play in the formation of other toxic ambient air pollutants, they would fall under the jurisdiction of EPA to regulate.

How does air pollution with the criteria pollutants impact our health?

One of the troubling aspects of the criteria pollutants is that almost anything bad that can happen to you biologically seems to be associated with exposure to elevated levels of these pollutants.

When we first started to study the health effects of these regulated pollutants, naturally the researchers looked primarily at impacts on the respiratory system. And there are many. We have ample evidence that there are causal associations between exposure to particulate matter, ozone, and nitrogen dioxide (all criteria pollutants) and both acute and chronic lung problems.

As we dug a bit deeper into the scientific evidence, we saw that the effects were much broader. We now have evidence associating exposure to these pollutants with adverse cardiovascular effects, neurodegenerative disease, and adverse birth effects. The question of how that's possible, and which biological mechanisms explain these health effects, has also actually become clearer over time. 

Are there any other health concerns from the six greenhouse gases listed in the endangerment finding?

There are many health impacts that we know are associated with climate change, whether that’s extreme heat, extreme weather events, or population displacement. We expect and predict that those will increase with the increase of greenhouse gas emissions that could come from getting rid of the endangerment finding.

What might we expect to happen to air quality and health if the endangerment finding is rescinded?

We have seen tremendous public health impacts from our national ambient air quality standards. We've seen air pollution levels largely decline in the United States. Measurable, quantifiable, and substantial public health benefits have followed. 

Now, we could see what happens when you reverse those trends. So, if the endangerment finding is repealed, and we see an increase in greenhouse gas emissions and other ambient air pollutant levels, we will learn what corresponding impact that has on population health.

If ambient air pollution increases, where do we go from there?

With the criteria pollutants, we have shown that we can fix the problem of air pollution, given we have the individual and societal will. In fact, we have shown that we can make a difference in not just lowering pollution levels but improving public health from lowering the levels.

These are problems that we can overcome. Ultimately, I think this presents a hopeful story that we can fix any negative impacts from deregulation if there is a societal and political desire to do it.