October 1, 2007

This Question and Answer document on copper antifouling coatings summarizes the current scientific and regulatory information on copper’s use in antifouling coatings. It has been created by the NPCA’s North American Marine Antifouling Coatings Work Group whose members include the major worldwide coatings and copper active ingredient manufacturers. It also is a “consensus” position of this group. As such, there may be members within the AFWG who may not concur in all the points made regarding the best management practices for their coatings. For information and recommendations on specific coatings, the individual manufacturers should be consulted.

Copper Q & A’s

1. Is copper bad for the environment and should I be concerned?

• Copper occurs naturally in all waters around the world. While high concentration levels can be harmful to humans and the environment, copper is an essential micronutrient to life and a certain amount is essential for the well-being of animals, including humans.

• The use of copper in antifouling coatings must go through an exhaustive review by the US EPA before being approved. The EPA has allowed copper for this use because it has determined that copper in antifouling paints is safe for the environment and for users when used as directed.

• Copper is an effective and safe antifouling active ingredient. The use of copper has allowed the effective removal of tributylytin (TBT) from the market and from the environment as required by International Maritime Organization (IMO) Treaty, which will fully enter into force in September 2008. In discussing the treaty, the IMO stated that one study had found that copper was 1,000 times less harmful than TBT.

• The use of effective copper antifouling coatings is crucial in the prevention of the transport of invasive species, which is a growing environmental and commercial threat to US waters.

• Effective copper antifouling coatings prevent attachment of fouling organisms to underwater hulls and thus greatly reduce the friction of vessels traveling through water. This decreases the amount of fuel used and greenhouse gases placed into the environment.

2. When the IMO treaty comes into force, TBT will be banned and I have read in several yacht magazines that copper will be next. Is this true?

• Copper was used centuries before TBT and is still a safe and effective alternative to TBT. Further, copper in antifouling paints is heavily regulated around the world to ensure human and environmental safety. There are no expectations that copper will be banned for use in antifouling paints.

• Copper is internationally recognized and registered as a safe and effective compound to control fouling by organisms such as barnacles, mussels and tube worms.

• There is no proposal to ban or restrict the use of copper by the IMO at this time.

3. Copper in pleasure craft antifouling paints is to be phased out in Shelter Island Yacht Basin (SIYB) in San Diego. When will this spread to the rest of California and then throughout the USA?

The SIYB issue is complex and will take some time to work out.

• First, the plan calls for a long range phase out of copper but leaves open the door for scientific and technology developments concerning the threat to alter that requirement. The program is limited to one marina, SIBY. The action is being taken to meet a “default” standard for copper concentration under California and US EPA water standards. The US EPA realizes this standard does not take into account the actual toxicity of the copper since sea water contains compounds which bind to copper and greatly reduce its toxicity. Therefore US EPA already uses a real world “toxicity calculation” for fresh water determinations and is actively investigating employing it for marine waters. When this is incorporated into the evaluation of SIYB’s marine waters, it will significantly raise the allowed concentration standard. This could greatly affect the degree of controls required, even removing the called for phase out of copper altogether.

• Second, for the foreseeable future, there are no coatings as effective and economical as copper antifouling coatings. Copper is safe for both the environment and applicators. Copper is currently going through a re-registration process at the federal level with the US EPA and it is very likely that this re-registration will be granted.

• Third, current biocide-free coatings present their own challenges including frequent and rapid movement and/or cleaning to be effective. As a practical matter this requirement is not suited for many vessels (including recreational).

• Fourth, there are other options that can mitigate elevated copper levels in marinas. These include eliminating uncontained in-water hull scrubbing and utilizing lower release rate coatings.

• Finally, many marinas and areas will not have this problem. Shelter Island Yacht Basin, where the phased-in ban is being considered, is an extremely large and crowded marina with very low water exchange. Where these conditions do not exist copper levels associated with copper containing antifouling coatings are much lower and well below even the stringent federal Clean Water regulatory limit.

4. What proportion of the copper in the marina waters comes from antifouling paints?

• On a global scale, the copper level in the aquatic environment resulting from antifouling paints is miniscule and insignificant. For example, it has been calculated that it would take over 100,000 years of use of copper in antifouling paints at the current level to double the copper content of the world’s oceans and this doubled absolute amount would still be minuscule. Another source of copper is plumbing such as the water pipes in homes.

• On a micro-scale, there are a small number of enclosed environments – such as specific man-made marinas in California – where copper from antifouling paints can contribute a higher proportion of the total copper present. However, the total copper level in these environments has to be high before measured negative effects to the environment occur. The vast majority of marina waters and marinas will not experience any problems related to the use of copper-containing antifouling coatings.

5. Is it true that a large percentage of copper in antifouling paints is derived from environmentally beneficial recycling?

• Yes. The majority of the copper in antifouling paints comes from recycled copper wire and water pipes.

6. Isn’t it true that copper is bio-accumulative and toxic? If so, shouldn’t it be banned?

• No. Copper is not toxic except under certain extreme levels of persistent exposure. In fact it is a micronutrient necessary for all life.

• Copper does not bio-accumulate in the environment because organisms have mechanisms to regulate the amount of copper in their bodies and because the majority of it is quickly detoxified when it leaves the paint film surface. This happens in two ways – by entering and binding to the sediment and also by becoming bound to organic matter in the water.

• Copper is effective as an antifouling biocide because it provides an elevated concentration of bioavailable copper ion at the hull surface (see diagrams below) which has a deterrent effect, thus inhibiting the attachment of organisms. After accomplishing this task, it becomes benign as outlined above.

• When metallic copper or cuprous oxide leaches into marine water with oxygen present the predominant form of the copper is the cupric ion Cu²⁺. At the hull of the vessel where the copper is released, the cupric ion is both concentrated and bioavailable and thus overwhelms the natural biological processes of the fouling organisms that under normal conditions can utilize the copper as a micronutrient or expel excess copper. However, this concentrated cupric ion, after repelling organisms, quickly complexes and becomes dilute as it moves away from the hull. Because of the way it works, organisms can safely exist in close proximity to vessels with copper-containing coatings, such as on pilings of piers and docks (see diagrams below).

7. If I apply copper-containing antifouling paints to my boat, am I putting my health at risk?

• Provided that you read the label and any accompanying instructions carefully before using the product, and adhere to the application instructions, there should be no risk to human health when applying copper containing antifouling paints. As part of the US EPA registration process, safe use requirements are examined and mandated where needed. Further our products are often also registered with the state governments which also often specify safe use requirements.

8. Why do antifouling coatings have such widely differing copper levels?

• Copper content is controlled by the use pattern and service life of the paint, the region, the binder system and the inert components.

9. Why is it necessary for organic co-biocides to be used with copper in some products?

• Copper is most effective against hard fouling organisms, such as mussels and barnacles, but is less effective against soft fouling species, such as algae, seaweed, and slime. The organic co-biocides are specifically designed to work against these soft fouling species.

12. Do government vessels (Navy, Coast Guard, etc.) use copper-based antifouling coatings?

• Yes. They are used extensively by all navies in the world, and on commercial and pleasure craft vessels the world over.

13. Can copper-based antifouling coatings be used safely in fresh water?

• Yes. Copper is effective against fresh water fouling organisms such as zebra mussels and algae, and is safe to use in both fresh water and salt water when used in accordance with instructions.

14. Is copper that has settled in the sediment going to be a problem in the future?

• Sediments generally have a large capacity to take in copper without reaching toxic concentration levels to which plant or animal life will be exposed. Even if there were no copper antifouling coatings there would be background levels of copper in water sediment because it is naturally present in the environment.

• The level of copper in sediments from antifouling coatings can be minimized by using effective, long-lasting bottom paints and eliminating any uncontained in-water hull scrubbing.