Four years ago today, an explosion on the Deepwater Horizon oil rig in the Gulf of Mexico killed 11 workers and unleashed an underwater geyser of oil that took 87 days to contain. The oil harmed ocean fisheries and contaminated beaches along the Gulf Coast. A contentious cleanup and compensation effort has cost BP an estimated $14 billion so far, but also left many Gulf businesses with painful losses of their own.

As President Barack Obama observed, it was "the worst environmental disaster America has ever faced."

In response, the president went through the standard checklist of White House actions. He created a commission to study the safety of offshore drilling, initiated other studies by the Coast Guard, the Interior Department and the National Academy of Engineering, and reorganized federal oversight of offshore drilling. His administration promised "significant new safeguards to protect the environment beyond what has ever existed before."

That was then. During the election year of 2012, the administration's policy shifted from caution to a more positive stance toward offshore drilling.

The oil and gas industry said it was satisfied with new regulations issued in 2012. In that same year, BP was permitted to acquire new leases in the Gulf of Mexico.

Since then the government has opened up new areas of the Gulf to exploration and has moved steadily to open the Atlantic shoreline to offshore drilling.

In February, the new federal agency that oversees offshore drilling, the Bureau of Ocean Energy Management (BOEM), issued an environmental impact statement that, if approved by the Secretary of the Interior, will allow seismic airguns to explore for oil on the Atlantic coastal shelf and its canyons. These devices emit a noise of 250 decibels, sufficient to disrupt marine mammal life for hundreds of miles underwater. BOEM, indeed.

A former head of the federal agency overseeing offshore drilling, S. Elizabeth Birnbaum, wrote in a guest column in Thursday's New York Times that the administration's reforms have stopped short of dealing with the biggest threat identified in the Deepwater Horizon disaster: the failure of its blowout prevention system. A 2011 report by the National Academy of Engineering found that the system, similar to that found on other deepwater drilling rigs, "was neither designed nor tested for the dynamic conditions that most likely existed at the time that attempts were made to recapture well control."

As Ms. Birnbaum and co-author Jacqueline Savitz, of the conservation group Oceana, wrote, "Administration officials promised an immediate response to the N.A.E. report, including regulations to set new standards for blowout preventers by the end of 2012. Today, 16 months after that deadline and four years after the blowout, we still have not seen even proposed rules."

It's time for the administration to produce on its promises for greater protection from another oil drilling disaster.

It is hard to give credence to assurances of environmental safeguards for the Atlantic while the remedies for the nation's "worst environmental disaster" have yet to be applied.

Of course, even if an improved technology makes offshore drilling safer, it will never totally eliminate the hazards.

And coastal state advocates for Atlantic drilling should consider the ongoing example of communities along the lower Mississippi who struggle to get the industry to deal with the environmental damage caused by its normal operations, particularly to wetlands that are essential for flood control and maritime life.

Their experience should serve as a strong caution to advancing plans for exploration and drilling off the Atlantic.

Tourism is the economic lifeblood of many coastal regions - including those in South Carolina. Coastal states should be reluctant to jeopardize the comparatively clean tourism economy for offshore drilling, which can be anything but.