Table 1 The criteria to be met to achieve corresponding scores. The criteria are considered met if they are inferred in a publication
| Â | Scores | ||||
|---|---|---|---|---|---|
2 | 1 | 0 | |||
Sampling | 1 | Sampling methods | Dust: − Location − Date − Apparatus − Mass/area collected Atmospheric deposition: − Sampler description (incl. Collection surface area) and whether bulk or wet deposition collected − Location − Date − Height (of sampler and site, if appropriate) − Sampling duration (per sample and per campaign) − Materials used (e.g. filtered water in sample collection) Suspended particulates (air): − Location − Sampling instrument (make, model) − Aerodynamic size fraction − Flow rate − Height (of sampler and site for atmospheric air) − Filter substrate − Sampling duration (per sample and campaign) − Date and meteorological conditions | The study reports only a subset of the required criteria (e.g., date, location, materials used), however is still reproducible. | Insufficient reporting of sampling methods. |
|  | 2 | Sampling duration | Atmospheric deposition: typically coarse resolution (e.g. 1 week or 1 month) Suspended particles (air): 24–72 h* for low volume (16.7 L/min) sampler Sample duration may be shorter, depending on nature of sample (e.g. if highly polluted, high organic content etc), whether a high or low volume sampler is used and research question (e.g. if interested in a specific activity). *72 h defined as optimum by Liu et al., 2019a, whilst 24 h typical for PM10 sample collection (EN 12341). | Application of consistent sampling resolution to the best of the authors ability, which is appropriate to address the research question. | Inconsistent sampling durations unrelated to research question or sample type, or insufficient reporting. |
3 | Sample processing and storage | Atmospheric deposition: Sample collection using filtered water. Store sample shortly after collection in the dark at 4 °C or filter, dry and store in cool, dark place. Suspended particles (air): Transfer filter to a petri dish. Store in cool, dark place. | Insufficient storage at room temperature and/or or storage. Unnecessary exposure or contamination risk during transportation. | Insufficient reporting. | |
Contamination mitigation | 4 | Laboratory preparation | − Cotton lab coat or non-synthetic clothes − Equipment and lab surfaces wiped and rinsed − Plastic avoided in the protocol where appropriate − All apparatus used is rigorously cleaned with ultrapure water and/or filtered solvents − All reagents and solvents used are filtered | Criteria only partially met, e.g., solely wiping laboratory surfaces and equipment, not wearing a cotton lab coat. | No precautions or insufficient reporting. |
5 | Clean air conditions | − Clean room or laminar flow cabinet − The use of a clean room should be classified in accordance with ISO 14644 and/or providing an indication of the maximum permitted airborne particle concentration. | Mitigation of airborne contamination by carefully keeping samples closed as much as possible IF negative samples were run in parallel and examined for occurring contamination. | No regard for airborne contamination, sole use of normal fume hood, or insufficient reporting. | |
6 | Negative control (blanks) | 1) Field controls collected either in parallel to samples (paired) or throughout the sampling period (at least in triplicate), but without exposure to air/deposition. 2) Laboratory (procedural) controls (at least in triplicate) treated and analysed in parallel to actual samples. Sample concentrations need to be reported accounting for controls, i.e. deducting the baseline by microplastic count, shape and polymer type. | Insufficient form of a control, e.g. < 3 replicates, reporting of negative control results but no indication of whether sample data have been blank corrected. | No negative controls or insufficient reporting. | |
Sample purification/ handling | 7 | Positive control | Controls (at least in triplicate) with an added amount of microplastic particles treated alongside the samples, and for which the particle recovery rates are determined. | Insufficient form of a positive control (e.g. if only a part of the protocol is tested). | No positive controls or insufficient reporting. |
8 | Sample treatment (if necessary – where not necessary a score of 2 is assigned) | Dust only: Sieving All sample types: Digestion of sample using a protocol such as wet peroxide oxidation (WPO) and/or enzymes. If another chemical was used, effects on different polymers should be tested before application and reported. All sample treatments need to be carried out below 50 °C to prevent any damage to microplastics or changes in glass transition temperature. | If WPO is carried out without cooling or digestion temperature exceeds 50 °C. | If proof is missing that polymers are not affected by the protocol (e.g. heated KOH > 50 °C)/ insufficient reporting. | |
Microplastic characterisation and application towards assessing human exposure | 9 | Filter/substrate composition | Appropriate for the subsequent analysis i.e. inert, flat/membrane. | Quartz fibre filters (when analysing directly via micro-spectroscopy) OR composition which interferes with analysis | Insufficient reporting. |
10 | Polymer identification | Automated, semi-automated OR rigorous operator-based approach: Detailed and repeatable method incl. Whether MP analysed directly in sample or transferred to new substrate, spread of particles analysed across samples OR per filter ≥25% of the surface area analysed. High percent of suspected MPs analysed, i.e. analysis of all particles for when numbers of pre-sorted particles are < 100 or at least 50% when particle numbers > 100; high HQIs accepted (> 70%); Details of library/database included OR details of software/programme. | Hit quality indices < 70% when library matching; low percent of suspected MP/sample area analysed; no indication of whether analysed microplastics are evenly distributed across samples; no indication of whether microplastic were analysed directly in a sample or manually transferred. Identification with SEM/EDX to distinguish polymer vs non-polymeric materials. | No polymer identification performed or insufficient reporting. | |
11 | Particle characterisation for human exposure | Detailed reporting, including maximum/minimum particle size, and particle size limit of detection. Length and diameter of fibres reported. Classified as fibres if aspect ratio > 3:1. | No mention of minimum size/limits of detection. Sizes based on suspected microplastic (not confirmed microplastic). | Insufficient reporting. | |