The United States is to consider scrapping one of the most significant pieces of international safety-at-sea regulations, introduced to prevent catastrophic oil spills.
More than 20 years ago the US government and the United Nations international maritime organisation (IMO) forced through legislation requiring all oil tankers to be constructed with double-skin hulls, in the aftermath of the Exxon Valdez disaster.
In 1989, the 213,800-tonne tanker ran aground on a reef in Prince William Sound, Alaska, and dumped 11 million gallons of crude oil into its environmentally sensitive waters, blighting more than 2,000km of shoreline.
The global outcry led to the US passing the Oil Pollution Act 1990 and the IMO subsequently adopting its Marpol Convention, which mandated the use of double hulls to protect a vessel's cargo tanks.
However, last week the US maritime administration (Marad) issued what it calls a Sow (statement of work) that appears to suggest a U-turn.
The Sow seeks bids from third-party contractors to carry out a review of "the safety, economic and environmental issues of tankers constructed with double hulls". It especially asks that the economic impacts of double hulls, such as increased construction cost and decreased cargo capacity be examined, as well as the carbon footprint of designing, constructing, maintaining and operating of double-hull vessels.
"Though these double hulls reduce the threat of oil pollution as a result of grounding (or collision)," Marad states in the Sow, "they significantly increase the amount of energy needed to propel a vessel and increase the amount of air pollution into the atmosphere. As a result, the maritime industry's carbon footprint and criteria pollutant emissions are increased. In addition to the need to burn more fuel, it is acknowledged double hulls can cause several other problems, which will be detailed in this study."
The review comes at a time when environmental agencies are paying closer attention to air pollution caused by merchant ships.
Although international shipping contributes only 2.7 per cent to global carbon dioxide emissions, according to figures from the IMO, it says "business as usual" will increase that pollution from the current level of 1.12 billion tonnes a year to 1.475 billion tonnes in 2020.
In July last year, the IMO adopted binding regulations to limit the expected gas emissions increase by reducing fuel consumption of ships by as much as 15 million tonnes in 2020, a 14 per cent reduction, and by 2050, by as much as 1,013 million tonnes.
This will lead to savings in fuel costs for the shipping industry of up to US$200 billion (Dh734.62bn) a year, says the IMO.
Marad appears to suggest by abandoning the additional weight of double hulls the savings would increase and pollution be cut further.
On the other hand, since the introduction of double hulls, pollution from major oil spills has been reduced to practically zero.
So, not surprisingly, the US announcement has caused concern in the tanker industry.
"Why Marad chose to question the use of double-hull tankers now is unclear, especially after the global industry has spent the last 20 years phasing out the use of single hulls," posted the maritime website and forum G-captain, based in the US.
Similar sentiments were echoed by Intertanko, the international tanker owners' body.
"We have noted reports about Marad's intended study on tanker double hulls but, except for what we gather from press articles, we have little knowledge on the reasoning behind this," said Bill Box, Intertanko's senior manager for external relations.
"From our members' experience, double-hull designs have evolved into safe and reliable ships with an excellent safety and pollution prevention record. We might provide comments when such a study would be released by Marad."