Toxicity and bioaccumulation of trinitrotoluene (TNT) in fish: a review on fish health, with an emphasis on leakage from marine-dumped legacy conventional munitions

Abstract Vast amounts of conventional munition ended up on sea floors worldwide due to military activity, primarily through intentional dumping of munitions for disposal after the World Wars. In German coastal waters, the amount of conventional marine munitions alone is estimated at 1.6 million tons. After more than 80 years, munition shells are corroding, and toxic compounds from munitions are leaking into marine environments. Since fish are fundamental components of marine ecosystems and an important source of human nutrition, a major concern in the marine munition context is how toxic munition compounds affect fish. Trinitrotoluene (TNT) is one of the most abundant toxic explosives in marine-dumped conventional munitions and is leaking into the environment. At marine munition dump sites, TNT and its metabolites are detected in water, sediment, and biota. Generally, TNT concentrations are low (in the ng/l range), but near munition objects higher concentrations have been recorded (µg–mg/l). Leakage of TNT from marine-dumped conventional munitions will likely increase in the future as munition shells continue to corrode. Physical (current, waves, heat) and chemical (acidification) parameters facilitating munition degradation are also expected to intensify due to climate change. High concentrations of TNT (> 1.0 mg/l in water) can negatively affect fish at multiple biological levels. Depending on dosage, fish species and life stage, the effects of TNT exposure range from no physiological effects to DNA damage, modified enzyme activities and embryonic malformations, to damaged gills, aberrant behaviour, reduced fertility, and increased mortality. Accordingly, fish (and other marine biota) are likely to be severely affected by exposure to TNT in their environment. The present review compiles the available information on interactions of fish with TNT and its metabolites. It covers uptake routes, degradation, excretion, and effects on fish health and fertility at various concentrations. The majority of the information on the effects of TNT on fish was obtained from studies conducted in laboratory settings. The present review therefore seeks to connect laboratory findings with observations in the field and to discuss the potential consequences of current and future leakage of TNT from marine-dumped conventional munitions.