The avermectins, milbemycins and spinosyns are collectively referred to as macrocyclic lactones (MLs) which
comprise several classes of chemicals derived from cultures of soil micro-organisms. These compounds are extensively
and increasingly used in veterinary medicine and agriculture. Due to their potential effects on non-target organisms, large
amounts of information on their impact in the environment has been compiled in recent years, mainly caused by legal requirements
related to their marketing authorization or registration. The main objective of this paper is to critically review
the present knowledge about the acute and chronic ecotoxicological effects of MLs on organisms, mainly invertebrates, in
the terrestrial and aquatic environment. Detailed information is presented on the mode-of-action as well as the ecotoxicity
of the most important compounds representing the three groups of MLs. This information, based on more than 360 references,
is mainly provided in nine tables, presenting the effects of abamectin, ivermectin, eprinomectin, doramectin, emamectin,
moxidectin, and spinosad on individual species of terrestrial and aquatic invertebrates as well as plants and algae.
Since dung dwelling organisms are particularly important non-targets, as they are exposed via dung from treated animals
over their whole life-cycle, the information on the effects of MLs on dung communities is compiled in an additional table.
The results of this review clearly demonstrate that regarding environmental impacts many macrocyclic lactones are substances
of high concern particularly with larval instars of invertebrates. Recent studies have also shown that susceptibility
varies with life cycle stage and impacts can be mitigated by using MLs when these stages are not present. However information
on the environmental impact of the MLs is scattered across a wide range of specialised scientific journals with research
focusing mainly on ivermectin and to a lesser extent on abamectin doramectin and moxidectin. By comparison, information
on compounds such as eprinomectin, emamectin and selamectin is still relatively scarce.