Exploring the Use of Species Sensitivity Distributions to Define Protective Limits for the Use of Organic Wastes as Soil Amendments

Abstract

The use of organic wastes as soil amendments can be an important measure to improve soil quality and reduce waste accumulation and landfilling. However, the potential contaminant loads of such wastes, can be a source of environmental concern. Consequently, legislation has been developed to regulate the use of these wastes in agricultural soils. However, the regulations only consider chemical parameters, which are insufficient to establish the level of environmental risk. A possible solution is the use of species sensitivity distributions (SSDs), employing ecotoxicological data from test batteries that could be incorporated into legislation. In the present study, 2 different hazardous concentrations affecting 5 and 50% of the soil community (HC5 and HC50, respectively) were determined using ecotoxicological data (effect concentrations, 10 and 50% [EC10 and EC50, respectively]) for 5 different wastes. The results demonstrate that, as expected, current legislative thresholds do not translate to environmental risk/protection and that SSDs may be an important tool allowing the simple inclusion and interpretation of ecotoxicological data from test batteries in legislation. On the other hand, SSDs must be used with caution because there are still doubts about their actual value in risk prediction and about which estimates provide adequate protection. For instance, the use of HC50EC10 values is not recommended; these values overlap with the more conservative HC5EC50 data, highlighting the fact that the use of lower effect concentrations may not always provide the most protective approach. Also, hazardous concentrations need to be calibrated at the field or semifield level, to verify environmental protection in different soils/environments and the adequacy of standard test organisms. Environ Toxicol Chem 2019;38:1569–1576. © 2019 SETAC

Trace contaminants in the environmental assessment of organic waste recycling in agriculture: Gaps between methods and knowledge

“…This issue could first be addressed by no longer relating the measured toxic effect to the trace element availability (or that of any other soil contaminant), but rather more empirically relating it to the soil OW application rate. Application of this strategy in RA and LCIA has been supported by the findings of Pandard and Römbke (2013), Huguier et al (2015), Pivato et al (2015) and Renaud et al (2019). This issue could alternatively be addressed by relating trace element exposure to trace element bioaccumulation in soil organisms, since this bioaccumulation is considered as a prerequisite for any toxic effect.…”

“…The authors also suggested to further reduce this PNECSoil by a dimensionless assessment factor, depending on the number of trophic levels assessed, the timespan of the exposure to OW-amended soil (short-term/acute vs. long-term/chronic), and on whether the ecotoxicological RA were performed on laboratory or field data. Renaud et al (2019) recently proposed to refine the rendition of dose-response curves obtained from OW-amended soils by establishing a species sensitivity distribution for each tested OW. These species sensitivity distributions are based on ecotoxicological endpoints determined for several species (e.g.…”

“…These species sensitivity distributions are based on ecotoxicological endpoints determined for several species (e.g. two endpoints for plants and four endpoints for soil invertebrates were used by Renaud et al (2019)).…”

“…A hazardous concentration (HC) was thereafter determined for each OW as a threshold value higher than 5 or 50% (HC5 or HC50, respectively) of the community of soil organisms accounted for in the corresponding species sensitivity distribution. Interestingly, Renaud et al (2019) showed that using an HC5 based on EC50 was more protective than an HC50 based on EC10 and thus seemed more suitable for ecotoxicological risk assessment. The PNECadd value -which corresponds to the so-called hazardous concentration at x% (HCx)-is hence protective for 1-x% of soil organisms considered in the database.…”