Characterising Microplastics in the Context of Risk Assessment

bart.koelmans@wur.nl

The diverse nature of MP – biota interactionsKoelm

ans et al, Environ. Sci. Technol. 2017, 51, 11513−

11519.

?

Kooi and Koelmans, ES

&T Letters, 2019, 6, 551−

557.

To define ‘best practices’ you first need Context

• What is the context or purpose of the measurement? • Then what type of accuracy, detail, precision is required?• Which approaches & methods are available?• Which are best?• How do we assure and demonstrate quality?• How do we rationally report given that context?This talk: What is the state of the art with respect to these questions

The diverse nature of microplastic

Hartmann et al, Environ. Sci. Technol. 2019, 53, 1039−1047

Usually > 20 descriptors for polymer type

Requires >5 descriptors for size class boundaries

Requires >10 descriptors for shape categories____________TOTAL: > 35 descriptors..

(Micro-)plastics have habits..

Kooi and Koelmans, ES&T Letters, 2019, 6, 551−557

The habits of microplastics

Simplifying MicroplasticEnvironmental

MP

BioavailableMP

Requires 12 descriptors for ‘everything’Kooi and Koelmans, ES&T Letters, 2019, 6, 551−557

Mishmash SSDsBesseling et al, 2019

Two corrections needed: Convert ingestible mass or number to ‘ total’ environmental MP mass or number

Convert lab-based effect threshold number concentration to an ‘Environmentally relevant ingestible effect threshold number concentration’, assuming a volume based adverse effect pathway (e.g. food dilution)

Monte Carlo simulations n=106

Consistent SSD for Environmental MP

Koelmans et al., in prep.

Redondo-Hasselerharm et al, Science Adv, 2020 Mintenig et al, 2020, submitted.

S. Primpke et al, 2018, 2019

Pan et al., in prep

• Unit problems• D.L. not reported

Quality Assessment

WHO Case study (2019): What is the reliability of reportednumber concentrations of MP in drinking water? • Best practices obtained from literature reviews – wisdom of the

crowd• Translated into ‘ideal’ criteria for high quality study• Quantitative assessment system: Assign scores to a method aspect

when a criterion is met (2, 1, or 0 points)• Assess criteria and studies• Makes clear which data are reliable (according to the system)• Inform risk assessors / policy makers

Quality Assessment of (drinking) water MP studies

Koelmans et al., Microplastics in freshwaters and drinking water: Critical review and assessment of data quality, Water Research, 155, 2019, 410-422,

Take home

1. For humans as well as for any organism, risks, if any, are only caused by a fraction of the whole plastic continuum, dependent on concentration.

2. We need to know these fractions. 3. The continuum has ‘habits’ and thus can be simplified, which helps.4. Whatever remains to be measured needs to be measured with high

quality5. Meeting generic QA/QC criteria is more important than exactly

prescribing how a measurement needs to be done

Paula Redondo, Merel Kooi, Frits Gillissen, Hazimah Mohamed Nor, Christiaan Kwadijk, Miquel Lurling, Noël Diepens, John Beijer, Edwin Peeters, Ellen Besseling, Enya Hermsen, Jeroen de Klein, Vera de Ruijter, Svenja Mintenig, Xiangzhen Kong, Changgui Pan