A pair of in-depth studies into the potential threat of chemical munitions dumped at sea have yielded cause for cautious reassurance.

Results from the Hawaii Undersea Military Munitions Assessment (HUMMA) and the Chemical Munitions Search and Assessment (CHEMSEA) were published this month in a special issue of the academic journal Deep-Sea Research II, which was edited by Margo Edwards, interim director of the University of Hawaii at Manoa’s Hawaii Institute of Geophysics and Planetology, and Jacek Beldowski, a project director with the Polish Academy of Science.

Both studies indicated that munitions dumped within the survey areas did not represent a direct risk for humans if left untouched. The authors emphasized, however, that the 40 munitions studied represented only a fraction of the hundreds of munitions believed to be in the areas.

Each of the articles included in the special edition noted the limitations of research based on small sample sizes, and recommended approaches for future study.

An introduction to the collection further argues for the need to discern where and how to mitigate potential damage.

The factors at play include water depth, proximity to human activity, environmental conditions, thickness of munitions casings, corrosion rates and the type of chemical agent. Until those variables are systematically documented, it is not possible to understand the relative risks from individual sites to human health and the environment.

Before the 1972 Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter, the preferred method for disposing of chemical munitions was to dump them at sea. The result was the mass discarding of millions of tons of munitions throughout the world’s oceans.

Today, chemical warfare agents are destroyed via chemical neutralization or incineration.

The ongoing HUMMA study focuses on a region south of Oahu where “dozens of different species of fishes, crustaceans, mollusks, cnidarians and echinoderms (were) observed living on and around conventional and chemical munition.” It is based on data from sonar and photography as well as chemical analyses of physical specimens.

The CHEMSEA study, conducted in the Baltic Sea from 2011 to 2014, focused on a brackish, semi-enclosed sea with considerable human pressure from densely populated shores and nutrient-rich waters, resulting in frequent oxygen deficits and water stagnation.

While the HUMMA study found little threat from the sunken munitions that were examined, the CHEMSEA study recognized the munitions under its examination “as a point source of pollution in the Baltic Sea,” although its magnitude seems to be low and limited to deep, oxygen-depleted basins.

And while the CHEMSEA study found no evident of a direct threat to humans, the authors did warn that fish could be harmed by chronic exposure.