Washington (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.

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