TBT OR N OT TBT?

Forest and Bird, Volume 19, Issue 3, 1 August 1988, Page 32

TBT OR N

OT TBT?

by

Gerard Hutching

O n the one hand it has been described as ‘‘a potential DDT of the waterways." On the other it has been welcomed as the most efficient anti-fouling paint yet introduced. It is Tributyl tin (TBT) paint, and worldwide it has health and environment authorities in a quandary over how much its use should be restricted. TBT paints were first introduced commercially in the mid- 1960s, and found ready acceptance with merchant fleets, commercial fishers, navies and recreational boaties. They provided large cost savings over copper-based paints, were more effective in warding off troublesome barnacles and especially attractive to small boat owners they enable boats to be painted in bright gaudy colours because of their chemical makeup. In the United States TBT paints are used on recreational boats and the remainder on docks, buoys, lobster pots and fishing nets ~ in short, anywhere algae and barnacles might prove a nuisance. On large boats, for example, such organisms attach themselves to vessel bottoms, increasing drag and hence decreasing the ship's speed. The US Navy estimates that if its entire fleet was treated with TBT paint (not all is yet), it would make savings of $150 million a year in fuel consumption alone. Savings are even greater for the larger US merchant fleet a huge $318 million a year. Furthermore, boats treated with TBT paints have to come into dry dock for a repaint only every seven years, by comparison with once every two years if they had been treated with copper-based paints. Environmental hazards Set against these economies are the environmental hazards. French scientists were the first to alert the world that all might not be well with TBT paints. In 1977 they started to notice a strange thickening in the shells of the Pacific oyster Crassostrea gigas in the Baie d’Archachon, a popular boating area and the site of a flourishing oyster

farming industry. Tests showed that poor tidal flushing was allowing TBT to accumulate in the bay. Healthy oysters transplanted into the bay showed 50 percent mortality within 130 days, whereas deformed oysters taken from the bay to areas without recreational boats resumed normal growth patterns. In addition no juvenile oysters were developing. Within five years the French had introduced a ban on TBT paints on all pleasure craft over 25 metres in length, except on those with aluminium hulls. In the years just preceding the ban, 95 to 100 percent of the oysters had deformed shells. In the first year of the ban, the number dropped to about 75 percent; in 1983 to 45-50 percent. Spatfall -- in other words, offspring showed a similar recovery. There was no spatfall in 1980 and 1981, but it resumed in 1982 and thereafter. Following the French experience, the British decided to investigate their own faltering oyster industry. Over 90 percent of the country’s small yachts used TBT paints. Extensive tests were carried out with oysters in waters both free of and containing TBT, and the results pointed as conclusively as possible to TBT being the culprit for oyster deaths. In response to these tests, in 1986 the British banned the production of TBT copolymer paints with more than 7.5 percent TBE. Meanwhile in New Zealand Dr Peter Smith of the Fisheries Research Division in Wellington had been conducting his own experiments. He collected samples of water from Westhaven (Auckland), Port Nicholson and Evans Bay (Wellington) and Picton and Havelock marinas. Although the levels of TBT were found to be low, they were still greater than those known to be lethal to larvae of shellfish. MAF then discovered abnormally thickened rock oysters in Westhaven marina and similar Pacific oysters in Half Moon Bay, Auckland.

In 1986 Peter Smith travelled to Britain where he saw experiments being carried out on sea snails. The condition of ‘‘imposex’’ was noted, whereby all the females had changed to males, sporting penises instead of female genitalia. Back in New Zealand he did not have to go further than Evans Bay in Wellington to collect a different but similar species of sea snail, and the result from experiments on these replicated those in Britain — no females could be found. There are a number of small craft moored in the bay. Samples for comparison were taken from open water in Northland, and the proportion of males to females there was 1:1. Salmon also affected Shellfish are not the only animals that have been affected by TBT. Recently researchers from the US National Marine Fisheries Service in Alaska found that farmed chinook salmon can absorb the compounds from antifouling paint used on the pens where the fish are reared. Pens at an Alaskan research station run by the service were coated in 1983 to prevent them becoming clogged with crustaceans. TBT was thought to be barely soluble in sea water, so the researchers saw no risk to the fish in the pen. Yet they soon saw fish dying for no apparent reason. Further investigations confirmed that TBT dissolving in the water was responsible. Because it is common practice for US salmon farmers to coat their pens with TBT paints, the researchers decided to sample salmon bought at markets for TBT content. Only four of the 15 they bought did not contain TBT. In New Zealand it is now a condition of salmon farmers’ licences that they do not use TBT paints on pens. Fears have been raised that TBT has a similar effect to DDT: it accumulates as it goes up the food chain. Possible proof of this accumulation effect has been recently found with the discovery of TBT in tissues

of five dead Californian sea otters. The highest TBT level was 1.2 parts per million, 50,000 times the concentrations known to be harmful to oysters. However, while there are similarities between TBT and DDT, TBT lacks some of the more undesirable effects of the insecticide: it breaks down faster, does not travel long distances but generally stays within a few kilometres of where it is released, and does not produce the host of toxic decay products that DDT does. The most disturbing aspect which the two share in common is their lethalness to non-target animals. Neither DDT nor TBT have yet been proved di‘rectly to kill humans. Despite that, TBT has been shown to have significant adverse effects on animal and human health. A Health Department report has said that, on rats ‘‘long term feeding studies at low TBT concentrations have shown immune system perturbations."’ It has also caused severe skin and eye irritation and acute burns to people who have worked with the paints. Associate Minister for the Environment, Philip Woollaston, took the initiative on TBT paints in December 1987 when he issued an interim report recommending a ban on the sale and use of the paints. A working party with representatives from MAF, the Health Department and paint manufacturers was convened by the Ministry for the Environment and their report was due by April 1988. However, this did not appear until July. Because the working party cannot agree, the report puts forward several options, one of which is to ban TBT paints on boats less than 25 metres in length, and the other to set a two-year phase out period for banning on all vessels.

Action too late However, environmentalists are concerned that any action taken to ban the paints will be too late to stop boaties from using the paints before this summer's boating season. The Ministry for the Environment has only a power to recommend, not to regulate, and has to prod other agencies into gear. In this case the likely body to finally make the regulation banning TBT paints is the Pesticides Board. The earliest the question can go before it is August, and its next meeting after that is November. Conservation Officer Mark Bellingham of Forest and Bird has been lobbying government Officials and politicians to move fast in banning the paints, but fears that bureaucratic inertia will stall a swift ban. "Officials have missed a golden opportunity to ban the paints before this spring, yet the working party has been in operation since December 1987,’’ he says. A further cause for concern is the opposition of parties such as the Navy to a total TBT ban. Following the lead of the United States Navy, the New Zealand Navy takes the view that the economies of TBT paints makes them too attractive to stop using them. It quotes US Navy reports on the lower level of TBT used in Navy paints compared to commercial, and the fact that their ships are out of port more than pleasure craft. It argues that Navy boats leach out very little TBT in port. Bellingham disputes that the Navy should be exempt from the ban, since naval ships spend a large proportion of their time in dock, and if tidal flushing is poor the boats have the potential to release damaging TBT. The Captain Superintendent of Devonport Dockyard, Captain Terry O’Brien, concedes

that there are problems with TBT but does not believe the paints the Navy uses have any ‘‘deleterious effect on marine life.’’ ‘‘However the Navy is very conscious of the emotional aspects of our policy and that we may have to change it. It is a fluid policy and we are looking at the new developments,’’ he says. Damn dangerous On the other hand, the Director of Navy Construction for the Defence Department, Sandy Bell, says it is of concern to the Navy that ‘‘the stuff is damn dangerous.’ Once the ban is put into effect, the Navy will no longer use TBT paints on their small craft. He adds that for the Navy there is a ‘"‘commercial aspect" to a full ban. The Navy have floating docks in Auckland, Wellington and Lyttelton, and at present overseas vessels sometimes use them for repaints. If TBT is banned, the Navy will lose any income from vessels which want to be coated with TBT paints. Captain Tim Nicholls of the New Zealand Line says that there are very few New Zealand merchant vessels, and not all of them use TBT paints. The greater hazard from commercial boats is posed by fishing boats, he maintains, as there are more of them and they spend a longer time in port. He disputes that the Navy or Harbour Boards would make a great deal of income from painting overseas boats, since they do not come here expressly to be painted. "‘It’s just too expensive."’ Captain Nicholls envisages there will be problems in finding suitable alternatives to TBT. Great care will be needed to ensure the next generation of paints don’t have the lethal side effects of TBT. ‘‘But after all, marine paints are designed to be toxic,’’ he points out. Alternatives to TBT already exist, and in fact the US Environmental Protection Agency has shown that traditional copperbased paints are a better deal for the pleasure boat owner because they are cheaper than TBT paints. This even takes into account the fact that the latter last longer. Taubmans, one of the largest paint companies in the world, have reluctantly agreed to go along with a ban. However, spokesman Neil Galloway maintains that a case has not been made against TBT yet, but that it all centres on ‘‘circumstantial evidence."’ ‘We are happy to restrict TBT in the marine environment. However, the alternative — cuprous oxide — breaks down to metallic copper which is poisonous. We are confident that a dramatic breakthrough will be made in a few years in marine paints,’’ says Galloway. He believes that a lot of emotion has surrounded the subject, and points to the recent US Environmental Protection Agency report as the most balanced and reasonable. He also admits that Taubmans played a large part in preparing the report. g-