Shipping companies that transport the world's coal are in the crosshairs of some financial backers who are cleaning up their businesses in the absence of a truly global drive by nations to renounce the dirtiest fossil fuel.

In a sign of investors taking the initiative, six European firms collectively representing over 5% of the estimated annual $16 billion capital financing requirements of the dry bulk industry have said they are either reducing their exposure to vessels that transport coal or are considering doing so.

Such carriers — titanic vessels stretching up to 270 meters long and able to carry hundreds of thousands of tonnes of cargo — are the cheapest way to transport coal and other commodities such as iron ore and grain in large quantities.