Data and R code for: Assessing the global capacity for monitoring microplastics (0.3–5 mm) on sandy beaches: Insights from the first proficiency test

This repository contains the participant dataset and the complete, reproducible R analysis pipeline for a global proficiency test (PT) on microplastic quantification, conducted under the IAEA NUTEC Plastics initiative. In the exercise, 49 laboratories across 41 countries analysed spiked beach-sand samples and reported particle counts by polymer type and size fraction. The samples were spiked with polyethylene (PE), polystyrene (PS), and a (non-recoverable) polyethylene terephthalate (PET) reference, across two size fractions (0.3–1 mm and 1–5 mm). A single data file (df_counts) drives the entire analysis. From it, one script reproduces every statistic, table, and figure in the associated manuscript, including per-laboratory recovery rates with bootstrap confidence intervals, a negative-binomial GLM screen of method-related effects on recovery, paired McNemar/Wilcoxon tests across size fractions, polymer-identification and false-positive analyses, and pass/fail recovery heatmaps. Contents PT_microplastic_analysis.R — the full analysis pipeline; reads df_counts and writes all outputs to ./output/. df_counts.rds — the participant data as an R object (exact types preserved). df_counts.csv — the same data in open text format. README.md — data dictionary, spike design, software requirements, and step-by-step reproduction instructions. Reproduction. Install R (≥ 4.1) and the packages listed in the README, place the files in one folder, and run source("PT_microplastic_analysis.R"). Random seeds are fixed, so results are bit-for-bit reproducible. This dataset accompanies the manuscript "Assessing the global capacity for monitoring microplastics on sandy beaches using a harmonized protocol: Insights from the first proficiency test" by "Marc Metian, Kristof Moeller, Sabine Azemard, Amanda Townsend, Janeth Mora, Nathalie Bernard, Francois Oberhaensli, Saif Uddin and Carlos Alonso Hernandez" currently under review at Marine Pollution Bulletin.