Ending the use of antifouling paints on boat hulls?

Lauantai 19.6.2021 klo 14.58 - Mikko Nikinmaa

A significant problem with boat and ship hulls is that barnacles and algae attach to them especially in marine environment and, in addition to aesthetic problem cause both increased fuel consumption and decreased maximal speed. Because of these problems, antifouling paints have been used to prevent the growth of organisms on hulls. The problem with the organisms growing on hulls is that they are both animals and algae. Thus, to be effective, the antifouling paints must kill every type of organism.

Paints containing organic tin compounds, especially tributyltin, were used in hulls until it was found that the compounds cause imposex and loss of fertility in oysters in areas close to boat harbours. In addition to these toxic effects, they can cause various other toxic effect at environmentally occurring concentrations. Because of this, paints with these antifouling compounds are banned throughout the world today. Since tributyltin breaks down in a few weeks in pure, oxygenated water in the presence of sunlight, it was thought that toxicity of organic tin compounds would disappear in a year or maximally two of their ban. However, it has now become clear that their toxicity persists for tens of years. This is due to the fact that the compounds are quite stable in anaerobic sediments for tens of years, and become available to aquatic organisms whenever the sediments are dredged.

The organic tin-containing paints have been replaced with copper-containing paints often with booster biocides such as Irgarol 1051 and Diuron. In the paints copper has usually the valency of one. Cu⁺ is by far more toxic then Cu²⁺, and the toxicity caused to the aquatic environment is close to that of the organic tin-containing paints. Furthermore, the toxic copper compounds can persist even longer than the organic tin compounds. Consequently, one should be able to stop using the toxic paints altogether.

One possible solution is attaching coating with miniature spikes on boat hulls. Such coating has been developed and has recently received a European Innovation Award. If and when the coating becomes a large-scale solution for antifouling in boat hulls, we may see the end of toxic antifouling paints altogether.

Cigarette Butts - a Major Source of (Micro)plastics

Sunnuntai 28.7.2019 klo 20.37 - Mikko Nikinmaa

In about 1970 a survey was made in Finland about the different types of trash in the environment, and I made a similar survey on the roadsides and beaches of South Wales. The most common type of trash was cigarette butts. At least 80 % of smokers have thrown smoked cigarette butts to the environment. They may not be as visible as larger trash, but as already the early surveys indicate, easily found, and in beaches a significant nuisance just as trash.

However, cigarette butts are not just a nuisance. Cigarette filters are plastic. Apart from tyre wear particles they are probably the most important source of aquatic microplastics. The problem with plastics from  cigarette filters is that they have high concentrations of all the toxins that cigarettes have. Since the toxins, e.g. the ones causing lung cancer in humans, are lipophilic, they adsorb to the plastics in the filters, and even when the filter is broken up to microplastics remain attached to the plastics. This means that whenever animals eat plastic particles, they will get much toxic compound, which are easily absorbed in the intestine, where lipophilic compounds easily cross intestinal epithelium. This “Trojan horse”-type behaviour makes the cigarette butt-derived microplastics much worse pollutants than any other plastics even if other plastic particles can also have smaller amounts of adsorbed harmful substances.

Pictures of ingested cigarette butts in fish intestine have been circulated. However, small microplastic particles are ingested by planktonic organisms such as early life stages of fish and water fleas. It has been shown that fish development is disturbed by cigarette butts, and indicative of the harmful toxins being involved, the developmental disturbances are more severe for smoked cigarette butts than for unsmoked ones (Lee & Lee 2015. Ecotoxicology and Environmental Safety 113, 362-368). With regard to zooplankton such as daphnia, they ingest microplastics, and ingestion of microplastic particles can cause at least experimentally induced population decreases (Bosker et al. 2019. Environmental Pollution 250, 669-675).

So tobacco smoking affects also environment and people, who are not in any contact with smoke. In the plastic pollution, it is an important component, I would say a major one in Europe and North America. Furthermore, it could be completely finished: stop smoking or if you cannot do that, do not throw your cigarette butts in environment.