The South Carolina State Ports Authority announced last week that Carnival is retrofitting many of its cruise ships, including the Charleston-based Fantasy, with scrubbers to reduce air pollution.

While it is good to see some acknowledgement of the risks posed by diesel particulate soot, the reality is that the scrubber proposal is part of a Carnival plan to avoid burning cleaner fuel otherwise required by law.

What's more, the fact remains that shore power - plugging in a cruise ship while it is docked - is the cleanest option available. Not only does shore power reduce the total amount of pollution emitted by hundreds of tons per year, it would disperse the remaining pollution over a much larger and less populated area.

Announcing the investment of scrubbers and filters by Carnival, SPA President and CEO Jim Newsome said that "the Fantasy's exhaust comprises 0.05 percent of total pollutant emissions in Charleston County."

This statement shows a fundamental misunderstanding of the danger associated with the pollutants from a significant diesel source: location, location, location.

When it comes to air pollution, and especially diesel air toxins, proximity matters. Other ports have located industrial cruise terminals away from population centers for that reason. Other ports have also installed shore power - including at the cruise terminal in Brooklyn, where a Carnival ship calls.

In Carnival's eyes, Charleston is not worth that investment. In fact, Carnival's proposal to use scrubbers is part of an overall corporate campaign to avoid burning cleaner fuel while in port and out at sea. The International Maritime Organization, and subsequently the U.S. Environmental Protection Agency, approved a regulatory plan that required ships to start burning cleaner fuel in 2010, and fully phases in by the year 2015. Carnival led a major lobbying effort to overturn that rule, and ultimately was able to encourage the EPA to allow flexibility to the law through the experimental use of scrubbers and filters.

The EPA has granted the trial under the assumption that the scrubbers and filters will achieve the same effects as burning the cleaner fuel, but we will not know until the experiment begins.

Further, once the scrubbers and filters are installed on a ship, that particular ship no longer has to burn cleaner fuel.

The use of scrubbers and filters adds to water pollution from cruise ships. Studying the washwater left over from scrubbing and filtering, the EPA has pointed out that "use of scrubbers to clean the exhaust from marine engines using high sulfur residual oil and diesel fuels may lead to high concentrations of a number of harmful compounds in the water body around the ships." These harmful compounds include polycyclic aromatic hydrocarbons (PAHs), the largest known group of cancer-causing substances. PAHs also change the genetic materials of mammals, and bioaccumulate in edible shellfish consumed by humans.

The washwater also contains dangerous metals, such as arsenic, copper, lead, nickel, and selenium. Impacts from exposure to these metals include impaired organ function and reproduction, birth defects, and if at a high enough exposure, acute mortality.

In tests of scrubbers on cruise ships, the EPA determined that the amount of PAHs and metals disposed of could pose a risk to humans and other affected mammals and shellfish, and could also exceed water quality standards on a localized scale. Limits recommended by the International Maritime Organization "may not be sufficiently protective."

The Post and Courier's recent coverage of this debate included statements from our city leaders, such as "I think it [shore power] should be installed when needed ... when it proves direct environmental benefit and it's cost effective," as well as "why is it necessary at this time?"

The data are here. It makes sense to include shore power in the design for the new cruise terminal. We also know the cost-sharing structure from other ports, including Brooklyn, San Diego, San Francisco, Seattle, Los Angeles, and Juneau, among others.

We know shore power will protect the most lives in our dense downtown where many people work, live, and visit.

The time for shore power is now. Any delay or refusal to acknowledge this fact makes it very clear where our elected leaders stand on a deadly threat to the public's health.

Katie Zimmerman is program director of the Coastal Conservation League.