An EPA document shows that a new Chevron fuel ingredient has a lifetime cancer risk more than 1 million times higher than what the agency usually finds acceptable — even greater than another Chevron fuel’s sky-high risk disclosed earlier this year.

The Environmental Protection Agency approved a component of boat fuel made from discarded plastic that the agency’s own risk formula determined was so hazardous, everyone exposed to the substance continually over a lifetime would be expected to develop cancer. Current and former EPA scientists said that threat level is unheard of. It is a million times higher than what the agency usually considers acceptable for new chemicals and six times worse than the risk of lung cancer from a lifetime of smoking.

Federal law requires the EPA to conduct safety reviews before allowing new chemical products onto the market. If the agency finds that a substance causes unreasonable risk to health or the environment, the EPA is not allowed to approve it without first finding ways […]