Solving the Nonalignment of Methods and Approaches Used in Microplastic Research to Consistently Characterize Risk

Abstract

The lack of standard approaches in microplastic research limits progress in the abatement of plastic pollution. Here, we propose and test rescaling methods that are able to improve the alignment of methods used in microplastic research. We describe a method to correct for the differences in size ranges as used by studies reporting microplastic concentrations and demonstrate how this reduces the variation in aqueous-phase concentrations caused by method differences. We provide a method to interchange between number, volume, and mass concentrations using probability density functions that represent environmental microplastic. Finally, we use this method to correct for the incompatibility of data as used in current species sensitivity distributions (SSDs), caused by differences in the microplastic types used in effect studies and those in nature. We derived threshold effect concentrations from such a corrected SSD for freshwater species. Comparison of the rescaled exposure concentrations and threshold effect concentrations reveals that the latter would be exceeded for 1.5% of the known surface water exposure concentrations worldwide. Altogether, this toolset allows us to correct for the diversity of microplastic, to address it in a common language, and to assess its risks as one environmental material.

Metal-doping of nanoplastics enables accurate assessment of uptake and effects on Gammarus pulex

“…36 This mechanism would imply that the mass-based TTF GUT values would be similar regardless of actual particle size, as long as particles would be ingestible. 36,52 The current finding that NP and MP with large size differences yield very similar TTF GUT under the same exposure conditions supports this hypothesis. We emphasize that this value only applies to the 28 d time point.…”

Lifetime Accumulation of Microplastic in Children and Adults

“…Rescaling the MP concentrations to the full MP size continuum was thus necessary to not underestimate the concentrations. 12 Furthermore, in doing so, we accounted for the smallest particles that are more relevant for accumulation in the body and potential toxicity. 9 , 13 The estimated power-law exponent for food in the present study is in excellent agreement with the exponents reported previously for PSDs of MPs in marine and freshwater environments.…”

“…The detailed approach for extracting this information is explained in the Supporting Information. We fitted the PSDs for 29 datasets from our literature review with the power-law function ( Figure S1 and Table S4 ), according to Koelmans et al 12 (see the Supporting Information).…”

“…Using the obtained power-law exponent, α, the MP concentrations found within any size range can then be translated into the expected MP concentrations for the default size range by using a correction factor (CF scale ), which scales the integral of eq S3 for the measured ( M ) size range against the default ( D ) range: 12 For the food types, we adjusted the measured MP concentrations to a default MP size range of 1–5000 μm. 12 For air, the datasets were adjusted to a default range of 1–10 μm because it has been demonstrated that only particles in this size range are filtered in the nose and may be swallowed via the nasopharyngeal pathway. 9 , 39 Based on the available PSDs from the aforementioned 29 datasets, two power-law exponents were defined, one for food (α food ) and one for air (α air ).…”

Microplastics are everywhere — but are they harmful?

“…Last year, the two teamed up with colleagues to use this model in computer simulations that predict how often fish would encounter microplastics small enough to eat, and the likelihood of eating enough specks to affect growth. The researchers found that at current microplastic pollution levels, fish run that risk at 1.5% of locations checked for microplastics 6 . But there are likely to be hotspots where the risks would be higher, says Koelmans.…”