{"doi":"10.1093/toxsci/kfae137","title":"Response to comment on: “Microplastic presence in dog and human testis and its potential association with sperm count and weights of testis and epididymis”","abstract":"To the Editor, We have read the comments of Drs Uppu, Peijnenburg, and Hays on our paper “Microplastic presence in dog and human testis and its potential association with sperm count and weights of testis and epididymis.” We are grateful for their engagement on this topic, which clearly transcends the output of any single publication. As we continue to advance in the field of microplastics research, we recognize the complexity and technical challenges involved in detecting and quantifying microplastics, especially in biological tissues. To steal/modify a sentiment from the television show Ted Lasso, “[Bioanalytical assays] are never going to be perfect. The best we can do is to keep asking for help and accepting it when you can and if you keep on doing that, you’ll always be moving toward better.” There is no better example of this than the current world of microplastics research, where there is urgency to efficiently understand the nature of the problem, especially in human health where methods are lagging. But at the same time, micro- and nanoplastics are difficult to isolate and quantify, and the pursuit of precision is often at odds with the technical limitations of known approaches. Our intent in recent studies was to bring concepts of clinical biospecimen investigation into the realm of micro- and nanoplastics measurement. Hundreds of papers are published every year on controlled exposures to cells, animals, and plants, yet we have a very limited understanding of true body burdens in relation to exposure concentrations. We are not alone in seeking confident estimates of plastics in the human body, as numerous groups worldwide are striving for actionable, quantitative assays that will enable integration with health outcomes. Until this past year, assessments in human tissues were limited to visual spectroscopic methods (Fourier Transform infrared or Raman spectroscopy) that rarely permit visualization of particles less than 5 µm in diameter (including all nanoplastics). Such particle number/size data are challenging to link with metrics of pathology or risk of disease compared with mass concentration data. The authors of the Letter are correct that more information on the applied methods would be beneficial for the broader research community. However, the article was published as a Research Brief. Much of the details regarding tissue collections, digestion, and positive and negative controls were provided in the cited manuscript on plastics measurement in placentas (Garcia et al. 2024). Regarding the second point, the authors cite excellent papers that explore the validation of digestion methods, and they find that no perfect method exists currently. Some polymers (polypropylene, polystyrene) may be relatively easy to identify within a biological matrix, whereas others may be masked or augmented. Polyethylene (PE) is challenging as biological lipids may interfere with the PE pyrogram and create false positives. This was the main reason we chose the potassium hydroxide saponification method followed by ultracentrifugation, as this eliminated 99.0±0.9% of our original mass of sample. Although other methods with liquid–liquid extraction will increase partitioning lipids into the analyzed sample, our approach substantially removes biomatrix. Dawson et al. (2020) had notable success with this method. Similarly, Lykkemark et al. (2024) showed that polymers can be lost during the digestion process, and subsequent digestion/isolation steps can further reduce the final yield. Our approach aimed to significantly reduce the amount of matrix without risks of losing plastics through acid or organic solvent extractions, which could further impact the yield. Although we acknowledge that our approach is not perfect, it remains internally consistent and thus enables confident comparisons between different human and dog specimens. Notably, our digestion method rendered an average PE concentration of 121.0 µg/g in human testes samples and 6","journal":"Toxicological Sciences","year":2024,"id":458628,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":5,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.953,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2024-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":1199144,"name":"Marcus A. Garcia","orcid":"0000-0003-1198-8440","position":1,"is_corresponding":false},{"id":1177913,"name":"Alexander Nihart","orcid":"0009-0009-4918-4895","position":2,"is_corresponding":false},{"id":1199306,"name":"Rui Liu","orcid":"0000-0002-6515-652X","position":3,"is_corresponding":false},{"id":1199307,"name":"Lei Yin","orcid":"0000-0002-8068-5999","position":4,"is_corresponding":false},{"id":1013730,"name":"Natalie L. Adolphi","orcid":"0000-0002-4899-3801","position":5,"is_corresponding":false},{"id":1199308,"name":"Daniel F. Gallego","orcid":"0000-0003-1517-0240","position":6,"is_corresponding":false},{"id":537498,"name":"Huining Kang","orcid":"0000-0002-4415-3573","position":7,"is_corresponding":false},{"id":342240,"name":"Matthew J. Campen","orcid":"0000-0002-2292-5050","position":8,"is_corresponding":false},{"id":891834,"name":"Xiaozhong Yu","orcid":"0000-0002-5523-9583","position":9,"is_corresponding":false},{"id":1200431,"name":"Chelin Jamie Hu","orcid":null,"position":0,"is_corresponding":true}],"reference_count":6,"raw_metadata":null,"created_at":"2026-07-19T02:03:50.608887Z","pmid":"39432568","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}