Of course, 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 either smells bad enough or the pollutants are obvious enough that savvy divers realize they don't want to use ordinary wetsuits or full-face masks that allows the water to touch their skin or enter their mouths or noses. While many dive companies have equipped their divers with helmets and vulcanized rubber dry suits to help protect them from these contaminants, not all firms have taken this step.

Yet despite the obvious dangers, there is another threat to divers that is much more subtle and insidious, but poses a long-term menace that is almost certainly life threatening. Tributyltin (TBT) is a chemical component found in the anti-fouling paints used on the bottom of most large ships. Anti-fouling paints have chemicals in the paint (TBT) that prevent 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 due to 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 non-aluminum 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 TBTs, but even if the ban occurs, it will be several more years before all ships painted with TBTs have been 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.

While most TBT research has been concentrated on its effects on marine organisms, Brookhaven National Laboratory issued a report noting that chemicals in this class have toxic effects on the human central nervous system, blood, liver, kidneys, heart and skin. While people will definitely respond to direct exposure to acute doses of TBTs, repeated sub-toxic doses produce negative reactions, which suggests a cumulative effect. It is currently unknown if TBTs are carcinogenic because no studies have been conducted to determine whether this is a problem.

Divers who clean ship's hulls or change anodes, or inspect sea chests on drill rigs, are in physical contact with the hulls of the ships they work on, either accidentally or intentionally. If a diver is only wearing a wetsuit, or no gloves, as some divers frequently do, particularly in warmer waters, he will 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, particularly if you are cleaning a hull, it is in the water surrounding the diver where it can be swallowed or inhaled by a diver using an ordinary full-face mask.

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 Jerusalem, was the principal author of a paper which 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 ships hulls for mines, to participate in exercises to practice setting mines, to repair ship's 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 public safety divers who made dives in San Diego harbor and polluted lakes in Michigan, but there have been no studies undertaken to establish a scientific cause and effect relationship between diving and disease here.

What Can You Do To Protect Yourself?
Protecting yourself from polluted water is a relatively simple matter in most cases. Instead of wearing a wet suit and a full-face mask with a wetsuit hood, you should be equipped with at least a full-face mask and a dry hood, or preferrably, a diving helmet and a vulcanized rubber dry suit with attached dry gloves. In most cases, this type of 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, the gear must be properly maintained, and you must follow appropriate decontamination procedures following diving.

Keep in mind, however, as just as there are different types of hazmat 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 period of time. If you're doing hull cleaning or repairs, a suit that will resist permeation by TBTs would be a good choice. Reputable dry suit manufacturers have test data available that lists the contaminants their gear may be exposed to and how long an exposure may be made before permeation occurs. Check with the manufacturer of your suit to see if they have tested for compatibility with TBTs and to what standards the tests were performed.

Unfortunately, diver's masks and helmets usually do not have the same capabilities as their suits, since these pieces of gear are frequently made from several different types of metals, plastic, and rubber. In addition, not as much test data exists regarding diving helmets and full-face masks for chemical exposure as exists for suits.

Performing work on ships' hulls and rigs 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! UW