The U.S Environmental Protection Agency (EPA) on Friday said it was proposing to declare emissions from piston-engine aircraft operating on leaded fuel pose a danger to public health.

Emissions from the 190,000 U.S. general aviation airplanes operating on leaded fuel account for about 70% of the lead entering the atmosphere, according to U.S. government estimates.

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Piston-engine airplanes operating on leaded fuel releases lead into the atmosphere. Pictured: A piston-engine aircraft from 1964. (Heritage Art/Heritage Images via Getty Images)

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Lead is not in jet fuel, which is used by commercial aircraft.

EPA said if the proposed finding is finalized, it would subsequently propose regulatory standards for lead emissions from aircraft engines.