Following the tragedy of September 11, 2001, the issue of homeland security came under intense scrutiny throughout the United States. One of the key vulnerabilities identified in coastal cities was our ports. Of specific concern were a number of potential scenarios including the disruption of the flow of commerce because of terrorist acts, the entrance of weapons of mass destruction, and the possibility of intentional spills of hazardous materials. Law enforcement groups have identified our ports as major targets for terrorist activities.

The flow of commerce through ports such as New York, New York; Boston, Massachusetts; Houston, Texas; Ft. Lauderdale, Florida; and Long Beach, California, is staggering. For example, in Long Beach alone, approximately $90 billion worth of imports and exports moved through the port in 2003.

To help ensure the security of our ports, local agencies in these cities have been conducting hull searches of foreign vessels when they arrive in port. The divers performing this work include firefighters, police officers, lifeguards, and military divers.

If you’ve never searched the underside of a large container ship or tanker in black water, it’s difficult to appreciate the dangers confronting the poorly trained or improperly equipped diver. For example, some ships are so large that it can be difficult for a diver who has run out of air to know which way to go to return to the surface. A Canadian public safety diver, using sport diving equipment and procedures, died in an accident of this type. His topside crew was equally untrained and did not have a practiced contingency plan.

Large ships also have seawater intakes and other machinery that, if activated, could injure or trap a diver within their proximity. It takes enormous confidence and ability to perform this type of diving.

Additionally, most harbors are more polluted than the coastal waters surrounding them and contain high levels of fecal coliforms from human and animal wastes, as well as a variety of oils, fuels, and other toxic chemicals. The sludge found on the bottom of many harbors also contains heavy metals. In numerous cases, the water smells bad enough or the pollutants are obvious enough that savvy divers realize they don’t want to use ordinary scuba equipment, which allows the water to touch their skin or enter their mouths or noses. While most dive teams have equipped themselves with full-face masks and vulcanized rubber dry suits to help protect them from these contaminants, not all agencies have taken this step.

(1) The maximum protection for divers is provided by a diving helmet mated directly to a vulcanized rubber dry suit. (Photos by author.)


(2) A wetsuit alone is not enough protection. TBTs move through the skin; a hood and gloves are necessary.



Another threat to divers is much more subtle and insidious but poses a long-term menace that is almost certainly life-threatening—tributyltin (TBT). This class of chemical is found in the antifouling paints used on the bottom of most large ships. The TBT in these paints prevents the growth of marine life on the ships, such as barnacles and encrusting worms that would slow the speed of the vessels and cause higher fuel consumption because of the increased drag through the water. According to the Environmental Protection Agency (EPA), “Tributyltin is the most toxic substance ever intentionally introduced into the marine environment.”

In 1988, the EPA banned its use on nonaluminum vessels less than 88 feet in length, but in other parts of the world there are no restrictions on TBT use. The United Nations Marine Environmental Protection Committee is currently considering a ban on TBT; even if the ban occurs, it would be several years before all ships painted with TBT are recoated with other compounds.

Why are TBTs dangerous to divers?

TBTs are part of a class of chemicals known as “organotin compounds.” These chemicals are absorbed through the skin of the barnacles, worms, and the cell walls of algae. They dissolve into fats, giving them the ability to move through cell membranes where they can kill these small organisms.

Most TBT research has been concentrated on its effects on marine organisms, but Brookhaven National Laboratory issued a report noting that chemicals in this class also have toxic effects on the human central nervous system, blood, liver, kidneys, heart, and skin. Although people will definitely respond to direct exposure to acute doses of TBTs, repeated subtoxic doses produce negative reactions, which suggest a cumulative effect. It is currently unknown if TBTs are carcinogenic because no studies have been conducted in this area. There have been no long-term studies of divers that have isolated the effects of TBTs from other illnesses or determined what treatment, if any, should be administered.

Divers who conduct hull searches are in physical contact with the hulls of the ships they inspect, accidentally or intentionally. In the case of a harbor with zero underwater visibility, the only way to conduct a hull search is to physically run your hands along the hull. If a diver is wearing only a wetsuit, no gloves, or no hood—as divers frequently do, particularly in warmer water—he would be directly exposed to the TBT chemicals. Since TBTs move through the skin, this will be the most common route of exposure. However, as the paint sloughs off the hull, as it does, the paint (with TBT) is in the water surrounding the diver, who can swallow or inhale it if he is using an ordinary scuba regulator.

(3) A vulcanized rubber dry suit. A diving suit should be able to withstand the greatest variety of contaminants for the greatest time. For hull searches, it should resist permeation by TBTs.


(4) A full-face mask is an alternative to using a helmet for diving in polluted water.



Only recently has the risk of cancer been positively correlated with divers who work in harbors. Dr. Elihu Richter, head of the unit of Occupational and Environmental Medicine at Hebrew University School of Public Health and Community Medicine in Jeru-salem, was the principal author of a paper that detailed the chemical exposure of 682 Israeli Navy divers working in the Kishon River since 1948. The Kishon River is highly polluted with heavy metals and other contaminants.

Richter and his team found a much higher level of cancer in these divers than in other control populations. If you think about it, some of the common tasks for military divers are to search ship hulls for mines, to participate in exercises to practice setting mines, to repair ship hulls and propellers, to clean sea water intakes on ships, and other similar tasks.

Exactly what caused the cancer in so many Israeli Navy divers is unknown, but there was a strong correlation between diving in the Kishon and cancer that cannot be explained by other causes. In the United States, we have anecdotal reports of cancer among dive team members in San Diego and Michigan, but there have been no studies undertaken to establish a scientific cause-and-effect relationship between diving and disease here.


Protecting yourself from polluted water is a relatively simple matter in most cases. Instead of wearing a wet suit and using ordinary scuba gear, wear a full-face mask or a diving helmet and a vulcanized rubber dry suit with attached dry gloves. In most cases, this equipment will be sufficient to protect you from the biological hazards present in most harbors as well as from a variety of contaminants. Of course, you must be properly trained to use this type of gear, the gear must be properly maintained, and you must follow appropriate decontamination procedures following diving. The latest edition of National Fire Protection Association (NFPA) 1670, Operations and Train-ing for Technical Rescue Incidents, specifically states that organizations operating at the Technician level for diving incidents shall develop and implement procedures for “utilizing full-body encapsulation equipment including dry suits, dry hoods, and dry gloves with full-face mask in contaminated water.”

Keep in mind, however, that just as there are different types of haz-mat suits that will withstand a variety of chemicals, there are different types of diving suits that are preferred for specific environments. In selecting a diving suit, it’s important to select a suit that will withstand the widest variety of contaminants for the greatest time. If you’re doing hull searches, the suit should resist permeation by TBTs.

Some dry suit manufacturers have test data available that list the contaminants their gear may be exposed to and how long it will take for permeation to occur. Ask the manufacturer for this information, and check it over carefully to determine how the testing was conducted and what standards the tests meet. Not all testing is done to stringent standards. For example, permeation tests should be conducted in accordance with standards of the NFPA, the European Norm, and the American Society for Testing Materials (ASTM).

Keep in mind that your gear is only as protective as the weakest item you are wearing—i.e., if the gloves are not compatible with the chemicals listed in the tests, then it doesn’t matter how much protection the suit provides. Any reputable manufacturer should be able to give you test data that include the standards against which their products were tested. If they cannot provide this information, look for another supplier.

Another important consideration for divers is that unlike a topside haz-mat situation where firefighters wear their SCBAs inside their suits, underwater, your helmet or full-face mask will be exposed to the contaminants. Unfortunately, divers’ life support equipment usually does not have the same capabilities as their suits, since these pieces of gear are frequently made from several types of metals, plastic, and rubber. In addition, not as much test data exist for diving helmets and full-face masks as for suits.

Of course, even if you wear the right gear underwater, any precautions you take would be worthless if you do not decontaminate properly following the dive. Your decontamination procedures must be set up and in place before you enter the water.

Performing ship hull inspections in a major port will always carry a certain degree of risk, but you can help to reduce the risk by equipping yourself properly and following the correct procedures for this type of diving. Your health and safety depend on it.

STEVEN M. BARSKY is a former commercial diver and the author of Diving in High-Risk Environments, available at

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