Does monensin in chicken manure from poultry farms pose a threat to soil invertebrates?

Monensin is a carboxylic polyether ionophore used in the poultry industry as a coccidiostat. It enters the environment via manure from broiler farms. In spite of its potential presence in the environment, information concerning monensin residues in manure and soil and its toxicity to soil organisms are insufficient. In the present study, two beneficial soil invertebrate species, earthworms (Eisenia andrei) and woodlice (Porcellio scaber), were used to assess the toxicity of monensin. Animals were exposed to a range of monensin concentrations via soil or food. Earthworm reproduction was found to be the most susceptible endpoint (NOEC=3.5 mg kg(-1) dry soil; EC(50)=12.7 mg kg(-1) dry soil), while no adverse effects were recorded in isopods (NOEC⩾849mgkg(-1) dry soil, NOEC⩾357mgkg(-1) dry food). The obtained toxicity data were compared with potential concentrations of monensin in soil. In view of this, manure from broiler chickens treated with monensin at a poultry farm was sampled. According to monensin and nitrogen concentrations in the chicken manure and the degradation time of monensin, the predicted environmental concentration (PEC) was calculated. PEC of monensin is around 0.013 mg kg(-1) soil if manure is used after 3 months of composting and 0.05 mg kg(-1) soil if used without storage. Data for earthworm reproduction was used to estimate the predicted no-effect concentration (PNEC). If fresh chicken manure is applied to terrestrial ecosystems, the risk quotient (PEC/PNEC ratio) is above 1, which indicates that monensin might pose an environmental risk under certain conditions. To prevent this, it is strongly recommended to compost chicken manure for several months before using it as fertiliser.

Toxicity of abamectin to the terrestrial isopod Porcellio scaber (Isopoda, Crustacea).

To determine effects of the antiparasitic veterinary drug abamectin on the isopod Porcellio scaber, animals were exposed for 21 days to Lufa 2.2 soil spiked at concentrations of 3-300 mg/kg dry soil. After exposure, abamectin residues in the isopods were analysed using a novel analytical method. Toxicity was evaluated on different levels of biological organisation: biochemical, cellular and the individual organism. Measurements included glutathione S-transferase (GST) activity and stability of cell membranes in the digestive gland, animal mass gain or loss, food consumption, behaviour and mortality. LC50 for the effect of abamectin on survival of P. scaber was 71 mg/kg dry soil. The most obvious sublethal effects were reduced food consumption and decreased body mass (NOEC 3 mg/kg dry soil). Additionally, loss of digging activity and reduced GST activity (NOEC 30 mg/kg dry soil) and cell membrane destabilization (NOEC 10 mg/kg dry soil) were recorded. Abamectin only slightly accumulated in the isopods, with bioaccumulation factors always being <0.1. Based on these results and current information on environmental levels of abamectin, it is not likely that isopods will be affected by abamectin, but further studies with exposure through faeces are recommended.