Don't worry, it's not much more carcinogenic than existing chemicals that were grandfathered in.

Nevertheless, in response to questions, the agency wrote, “EPA considered the full range of values described in the risk assessment to develop its risk management approach for these” fuels. The statement said that the cancer risk estimates were “extremely unlikely and reported with high uncertainty.” Because it used conservative assumptions when modeling, the EPA said, it had significantly overestimated the cancer risks posed by both the jet fuel and the component of marine fuel. The agency assumed, for instance, that every plane at an airport would be idling on a runway burning an entire tank of fuel, that the cancer-causing components would be present in the exhaust and that residents nearby would breathe that exhaust every day over their lifetime.

In addition, the EPA also said that it determined the risks from the new chemicals were similar to those from fuels that have been made for years, so the agency relied on existing laws rather than calling for additional protections. But the Toxic Substances Control Act requires the EPA to review every new chemical – no matter how similar to existing ones. Most petroleum-based fuels were never assessed under the law because existing chemicals were exempted from review when it passed in 1976. Studies show people living near refineries have elevated cancer rates.