Finding an Effective, Eco-Friendly Alternative to Tributyltin Antifouling Agents

Materials Studio

antifoulingAnti-fouling agents are applied to the hulls of ships in order to prevent the accumulation of algae and barnacles, but no reliably effective and environmentally friendly alternative has emerged since tributyltin was phased out in 2008. Image Credit: Flickr user Shane Deloges

For over forty years, the organotin compound tributyltin served as a highly effective biocide in anti-fouling paints used to kill algae and other organisms on ships’ hulls. While this compound served to speed maritime travel and increase the energy efficiency of ships, the effects on the surrounding aquatic environments have been devastating. The most widely observed phenomenon is shellfish imposex. This condition causes female shellfish to grow male sex organs, which has nearly led to reproductive collapse in multiple locations, and reduced not only shellfish populations but also those of fish and mammals that rely on them for food. This in turn threatens fishing industries in affected areas.1  Tributyltin also has a tendency to biomagnify up the food chain, accumulating in fish and then the mammals that eat them, where it has toxic effects on the brain and liver and may lead to infertility or obesity. Worse, tributyltin persists in the environment for up to thirty years after it is first introduced, wreaking havoc even at low, nanogram-per-liter concentrations.2

Because of these dire biological effects, tributyltin was banned by the International Convention on the Control of Harmful Anti-fouling Systems on Ships in 2001, with a phaseout deadline of 2008. However, enforcement has been insufficient, and there are still places where tributyltin is being used illegally.3  While there are some legal alternatives, the shipping industry has yet to find another substance that is as effective as tributyltin. Researchers at specialty chemicals companies have the opportunity to explore some of the emerging options in order to develop an effective, ecofriendly and legal replacement.

Exploring Possible Alternatives to Tributyltin Anti-Fouling Agents

Although several alternatives to tributyltin have emerged, each requires further study before it is ready for widespread adoption. As scientists seek to answer fundamental questions about these materials and optimize them for use as antifouling agents, they can harness the capabilities of modern computer modeling and simulations software. Consider the application of this technology to these possible replacements for tributyltin:

  • Copper-based anti-fouling paints

Although they are the most popular alternative so far, copper-based anti-fouling paints are not as effective as tributyltin, and there are questions about whether they might damage the marine ecosystem just as much as organotin compounds.4  It’s important that scientists have resources with which to compare chemical properties and behaviors. This will help them determine the limitations of current copper-based options and redesign more effective and eco-friendly variations.

  • Prickly coatings

Another option is to add microscopic “prickles” to ships’ hulls, which can stop barnacles and algae from attaching to the surface without contaminating the surrounding environment. Their effectiveness depends on the length and distribution of the prickles,5  so it is important for scientists to run computer simulations on a range of possible measurements and combinations.

  • Hydrophilic and/or charged particles

Some studies indicate that adding hydrophilic compounds to ships’ hulls can make them too slippery for barnacles to get a good grip. Similarly, particles that create a difference in electrical charge between the hull and the surrounding water can induce chemical reactions that prevent marine organisms from binding.6  Not only should scientists be running preliminary tests on a wide variety of compounds that might confer these properties, but they should also simulate different water conditions, which are typically overlooked in experiments that assume average acidity and salinity.

  • Combinations of nanometals and polymers

Another innovative option is to combine nanometals such as aluminum oxide, silicon dioxide, titanium dioxide and zinc oxide with polymeric coatings that reduce their cytotoxicity. Researchers considering the use of nanotechnology for anti-fouling can model different combinations and ratios of nanometals and polymers in order to optimize the material’s efficacy and safety in a given marine environment.

In order to compare these possible alternatives to each other, scientists may need to run a standard suite of tests on each. Because these tests must be conducted on a large number of compounds—for instance, several substances with different hydrophilicity, plus multiple combinations of nanometals and polymers, not to mention a range of prickle sizes—it can be helpful to automate common tasks. That way, the research team can guarantee methodological consistency, and scientists can spend more time interpreting data, instead of manually setting up simulations. Workflow authoring applications make it easy to aggregate the data necessary for common tasks and to run scientific analyses so that when it comes time for scientists to judge the developability of a particular anti-fouling agent, they have all the information they need.

Sharing Findings With Other Scientists

Once materials scientists have identified and optimized a promising alternative to tributyltin, the substance will need to be tested in biological settings, both in the lab and in the field, before it can be marketed. Biologists and engineers can benefit from the insights gleaned from chemical modeling and simulations as they consider the efficacy and environmental effects of anti-fouling agents. Modern software makes it easy for scientists in different departments and geographical locations to share knowledge in real-time so that they can pool their expertise to come up with a safe and effective alternative to tributyltin.

Ultimately, the speed of the research process can be significantly improved with modern software. By streamlining the testing process for possible anti-fouling agents and making it easier to share information with researchers in other departments, this technology can help materials scientists find solutions faster. That way, specialty chemicals companies can soon start offering effective anti-fouling agents that cause no further damage to marine ecosystems.

BIOVIA Materials Studio is an advanced computer modeling and simulation environment that enables researchers at specialty chemicals companies to conduct high-level analyses of possible alternatives to tributyltin and share their knowledge with colleagues in other departments. With BIOVIA Pipeline Pilot, a workflow authoring application, they can also automate common scientific protocols. Contact us today to learn more about how these innovative offerings can revolutionize research in your materials science lab.

  1. “Tributyltin (TBT) antifoulants: a tale of ships, snails and imposex,” June 24, 2015, https://www.researchgate.net/publication/241281378_13_Tributyltin_TBT_antifoulants_a_tale_of_ships_snails_and_imposex
  2. “Tough Environmental Regulation Inspires New Analytical Methods,” April 26, 2016, https://www.elsevier.com/about/press-releases/research-and-journals/tough-environmental-regulation-inspires-new-analytical-methods
  3. “Persistent Organic Pollutants (POPs) and Pesticides,” 2015, http://www.cep.unep.org/publications-and-resources/marine-and-coastal-issues-links/persistent-organic-pollutants-pops-and-pesticides
  4. “Are TBT alternatives as good?” January 1, 1999, http://www.motorship.com/news101/industry-news/are-tbt-alternatives-as-good
  5. “Anti-fouling systems,” 2002, http://www.imo.org/en/OurWork/Environment/Anti-foulingSystems/Documents/FOULING2003.pdf
  6. “Eco-Friendly Nano-Hybrid Materials for Advanced Engineering Applications,” July 12, 2016, https://www.crcpress.com/Eco-Friendly-Nano-Hybrid-Materials-for-Advanced-Engineering-Applications/Kumar/p/book/9781771882941