Toxicology of the herbicide acrolein: risk assessment in aquatic environments

MONTAGNA M; PECHEN DE D'ANGELO A.M; VENTURINO A

Herbicides and Environment

InTech

Año: 2011; p. 405 - 420

Acrolein is also known as acrylaldehyde, allylaldehyde, acrylic aldehyde, propenal, prop-2-enal and prop-2-en-1-al. As an herbicide, it is used to control submersed and floating aquatic weeds and algae. The mechanism of action is based on its reaction with protein and non-protein sulfhydryl groups and with primary and secondary amines. It is applied directly into the water and travels downstream as a wave. The presence of acrolein in this medium is transient since it decomposes rapidly as a result of its high reactivity. The main fate processes in surface water include reversible hydration, biodegradation by microorganisms and volatilization. Acrolein in weedy and non-weedy irrigation channels has short half-lives suggesting that long-range aquatic transport is unlikely. In sediment-water systems, acrolein undergoes hydrolysis, self-oxidation and biodegradation. Acrolein is not expected to be significantly adsorbed to suspended solids or sediments because of its low Koc and water solubility. Based on the low Kow and high reactivity, bioaccumulation by aquatic organisms is predicted to be low. However, acrolein presents a highly acute toxicity to aquatic organisms.Acrolein has been used at CORFO-Río Colorado (Argentina) irrigation channels since 1977 in order to control submerged weeds such as Potamogeton pectinatus, Zannichelia palustris, Chara contraria and Myriophyllum spicatum.A tiered approach to assess the impact of acrolein in an aquatic ecosystem produces a risk evaluation moving from conservative assumptions towards more realistic estimates of effects and exposure. Tier 1- assessment of the potential risk determined by comparison of acute toxicity data from literature, together with tier 2 incorporating the environmental fate behavior of acrolein from field studies, gives an unacceptable risk to most biota. The inclusion of a scenario representing an ecosystem in tier 3-studies, suggests that acrolein concentrations currently applied in irrigation channels kills most of biota a long way downstream the application points. Nevertheless, when a tier 4 was included to assess the effects and recovery of benthic invertebrates straightly in field studies, it could be seen that the benthic community in treated channels recovered their biotic attributes in only two months after ceasing the applications. Recovery could be possible from upstream unimpaired reaches supplying migrating invertebrates that recolonized affected areas. Taking into account the fact that recovery occurs within a reasonable period of time, it can be concluded that the impact of acrolein in irrigation channels can be considered ecologically acceptable.