The United States’ environment body wants to bring in tougher smog standards to protect citizens from air pollution.

Yesterday the Environment Protection Agency proposed strengthening air quality standards to within a range of 65 to 70 parts per billion (ppb). This is a limit on the amount of polluting particles in a set volume of air.

The body pointed to studies which suggest levels below 75 ppb (the level of the current standard) can pose “serious threats” to public health, harm the respiratory system, cause or aggravate asthma and other lung diseases.

Every five years the nation’s Clean Air Act requires the EPA to review the standards.

The agency plans to hold three public hearings and is asking the public to comment on its proposal for 90 days after publishing the details in an official register. It expects to issue final ozone standards by 1 October 2015.