(CNN) - The Environmental Protection Agency has quietly signaled it may allow states to release more ozone air pollution, commonly known as smog, dirtying the air in those states and neighboring ones, but the agency did not review the health impact of such a move.
The Trump administration's position is outlined in a highly technical guidance memo about plans states must create and submit for EPA approval under the Clean Air Act's good neighbor requirements. It was sent in August to EPA regional offices and posted on the agency's website, but not announced to the public.
The memo introduces the idea of increasing the threshold for how much smog a state can dump on its neighbors -- known as cross-state pollution -- before taking action to reduce emissions.
Under the Trump administration's new guidance, states that are currently finalizing their plans can consider adopting a looser standard than would have been allowed under the Obama administration. The new one part per billion standard means a state can emit 43% more pollution across state lines than before.
Smog is a byproduct of air pollutants including greenhouse gases, which contribute to climate change. It can originate from sources including power plants, refineries and factories. Smog can reduce the ability of the lungs to function, and especially impacts children, people who are active outside, or those who have respiratory diseases. It is linked to breathing issues and conditions such as asthma.
The guidance memo is just the latest move by the Trump administration to loosen restrictions surrounding air pollution. The administration has moved towards replacing the Clean Power Plan, moved towards freezing vehicle emission standards, and pulled out of the international Paris climate agreement. The EPA also recently overhauled the committees of scientists who advise it on clean air.
The Clean Air Act mandates that the EPA works to make sure smog from certain states doesn't jeopardize air quality in downwind states. If there's pollution above the threshold, then the states would need to reduce emissions to come into compliance.
Maryland is an example of a state struggling with this issue. According to an estimate from the Maryland Department of the Environment, 70% of smog in Baltimore on bad ozone days comes from out-of-state cars, trucks and power plants. Maryland has asked the EPA for help curbing the smog coming from upwind states. The EPA has denied the request and Maryland has filed a suit asking for a judicial review of the EPA's decision.
The Obama-era EPA supported a tighter 0.7 part per billion threshold for smog. The 0.7 part per billion cross-state threshold was rooted in a 2015 rule that tightened the standards to "provide increased public health protection against health effects associated with long- and short-term exposures" to smog.
The new memo is influential, because it guides decision making, but is not legally binding. It is guidance, rather than a regulation, so it did not go through the rigorous review process used to craft new rules. That also leaves it vulnerable to being reviewed or overturned by courts or a future administration.
EPA spokesman John Konkus disputed that the EPA was raising the pollution threshold. Instead, he said the agency is giving states the option to raise the threshold themselves through the memo.
"The memo identifies potential technical approaches that a state may wish to choose in drafting their implementation plans' approach to its good neighbor obligations," he said.
Konkus also said that the memo has "no health impacts," but the agency admits they have not yet performed any health-related analysis.
Several public health advocates say EPA isn't playing it straight with the public.
"EPA is allowing more harmful air pollution to be sent from big polluters in one state to neighboring states, refusing to control the pollution, then lying about what is an obvious rollback," said John Walke, the director of clean air at the Natural Resources Defense Council and a former agency attorney during the Clinton administration.
"It's absurd to pretend this so-called 'guidance' doesn't change what's acceptable: the purpose of the rollback memo is to let upwind states pollute more and refuse to control harmful smog and soot they emit into neighboring states," he added.
Kyla Bennett, science director at Public Employees for Environmental Responsibility, told CNN the agency is allowing some states, "under the guise of 'flexibility' and cooperative federalism, to emit more pollution."
"With a flick of the pen, this EPA guidance condemns hundreds of unlucky downwinders to early deaths every year," Bennett said.
The EPA memo claimed the nationwide overall pollution impact will likely be small -- the difference of 7 percentage points out of 100.
Some parts of the country, such as Western states like Arizona, will see virtually no impact, the memo said.
But other states, like Maryland and parts of Colorado, could see pollution levels spike.
The agency argues major gains have been made in reducing this sort of pollution. From 2007 to 2017, nitrogen oxides emissions, the key precursor for ground-level ozone pollution, has dropped by more than 40% nationwide, the agency said.
Bill Wehrum, a former energy industry attorney who fought to weaken air pollution rules, critics say, now oversees air pollution regulations at the EPA.
The EPA under then-Administrator Scott Pruitt initially tried to delay implementation of the Obama-era air quality rule, but now the Trump administration has decided to defend it in court, and recently argued in a federal appeals court against fossil fuel interests and five states supporting those interests. It is not clear why the administration changed course.
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