The potential risk of firefighting chemicals to aquatic and terrestrial species

The intensity and frequency of forest fires has increased due to anthropogenic factors, making the use of the most efficient fighting tactics extremely relevant. The use of these additives to extinguish forest fires can lead to the release of hundreds of thousands of litres of firefighting water additive solutions into the environment. It is important that the release of firefighting water additives isn't jeopardizing the survival of exposed aquatic and terrestrial species.

The ingredients found in firefighting solutions are most often concealed as patented trade secrets. In addition, there exists little ecotoxicological data for many of the forest firefighting products in current use. The aim of this study is to provide novel toxicity data for aquatic and terrestrial species exposed to firefighting water additives.

This study examined nine firefighting water additives used in Canada and evaluated their toxicity to terrestrial and aquatic biota. Additionally, a deterministic risk assessment was performed to identify potential hazards at environmentally level exposure concentrations. The risk assessment considered the worse-case exposure in an aerial application (5.0L/m^2) during a forest fire found in existing literature.

(Tubifex tubifex test set-up for firefighting product WD881)

Aquatic Species

Three aquatic invertebrates commonly found in freshwater waters across North America were tested. This included Daphnia magna, a pelagic zooplankton, Hyalella azteca, an epibenthic amphipod, and Tubifex tubifex an endobenthic oligochaete.

The greatest hazards were determined to exist in smaller water bodies such as their was less potential for dilution of the exposure solution. The species differed in their sensitivity to each product tested. For instance Daphnia magna were found to be the most sensitive to surfactant based products such as Phos-chek WD881 and WD881C, whereas Tubifex tubifex showed relatively low sensitivity to nearly all products tested. Phos-chek LC95A was the only product to pose a hazard to all aquatic species in at least one of the considered exposure scenarios.

Plant Species

This study assessed the effects of these products on a species terrestrial springtail, three species of plants and three species of isopods with the intent of generating toxicity data that could be used to characterize the relative risk to terrestrial soil biota.

Overall, the fire retardant LC95A posed one of the greatest hazards to most of the species tested. Soil invertebrate survival was relatively sensitive to firefighting product exposure, whereas the emergence of exposed plant species was most often unaffected. The only product found to impact emergence was the fire retardant LC95A when exposed to the broad leaf species Raphanus sativus.

(Radish seeds exposed to Phos-chek LC95A , t=0h)