Research and Studies

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Temporal Trends in Sperm Count: A Systematic Review and Meta-Regression Analysis

Levine H, Jørgensen N, Martino-Andrade A, Mendiola J, Weksler-Derri D, Mindlis I, Pinotti R, Swan SH. Human Reproduction Update, Volume 23, Issue 6, November 2017, Pages 646-659. doi:10.1093/humupd/dmx022

The landmark study that brought global attention to declining sperm counts. Researchers screened 7,500 studies and conducted a meta-regression analysis on 185 studies covering nearly 43,000 men, collecting semen samples between 1973 and 2011. They found a 52.4% decline in sperm concentration and a 59.3% decline in total sperm count among men from North America, Europe, Australia and New Zealand who were not selected based on their fertility status.

The study's authors, including Dr Shanna Swan, called the findings an urgent wake-up call for researchers and health authorities. They noted that the decline is consistent with reported trends in other male reproductive health indicators including testicular cancer rates, cryptorchidism and total testosterone levels.

Temporal Trends in Sperm Count: A Systematic Review and Meta-Regression Analysis of Samples Collected Globally in the 20th and 21st Centuries

Levine H et al. Human Reproduction Update, Volume 29, Issue 2, March 2023, Pages 157-176. doi:10.1093/humupd/dmac035

The 2022 follow-up to the landmark 2017 study, expanding the dataset to include samples collected globally up to 2018 and extending the analysis to South America, Asia and Africa for the first time. The updated analysis found that the decline in sperm counts is accelerating rather than plateauing, with the rate of decline more than doubling after 2000. The study found significant declines across all continents studied, suggesting the problem is now genuinely global.

Dietary Pesticide Exposure and Sperm Quality in Young Men

Chavarro JE et al. Human Reproduction, Volume 30, Issue 6, June 2015, Pages 1342-1351. doi:10.1093/humrep/dev064

A study of 338 men attending a fertility clinic that found men with the highest intake of high-pesticide-residue fruits and vegetables had 49% lower total sperm count and 32% lower sperm concentration than men with the lowest intake. The study controlled for other dietary factors, body mass index, smoking, alcohol and other confounders, isolating pesticide residue intake as the key variable.

Atrazine Induces Complete Feminisation and Chemical Castration in Male African Clawed Frogs

Hayes TB et al. Proceedings of the National Academy of Sciences, Volume 107, Issue 10, March 2010. doi:10.1073/pnas.0909519107

Published in the Proceedings of the National Academy of Sciences, this study by UC Berkeley biologist Tyrone Hayes found that exposure to atrazine caused complete feminisation in male African clawed frogs at concentrations below current regulatory limits for drinking water. This research is significant but should be understood in context. Subsequent studies have produced mixed results and the scientific debate remains active. In humans, atrazine has been associated with reduced testosterone and sperm motility in occupationally exposed populations. Atrazine is banned in the European Union but continues to be widely used in the United States.

Endocrine Disruptors as a Threat to Neurological Function

Zoeller RT et al. Journal of Neurological Sciences, Volume 17, 2012. doi:10.1016/j.jns.2012.02.014

A comprehensive review examining how endocrine disrupting chemicals interfere with thyroid hormone signalling, with particular focus on neurological development. The thyroid hormone system governs brain development during fetal life and early childhood. Disruption of this system by chemicals including PCBs, dioxins, flame retardants and certain pesticides has been linked to reduced IQ, attention deficits and other neurodevelopmental effects. The review calls for a precautionary approach to chemical regulation given the irreversibility of developmental neurological damage.

The UK Government PFAS Plan

UK Government, Department for Environment, Food and Rural Affairs. Published February 2026.

The UK Government's first ever dedicated PFAS Plan acknowledged that PFAS contamination is now widespread across England's water systems. Testing found PFAS contamination in 88% of surface water samples and 46% of groundwater samples tested. Every fish sample tested contained detectable levels of PFAS. The plan sets out the government's strategy for monitoring and reducing PFAS contamination, though campaigners noted the plan contains no binding reduction targets or specific timelines.

Serum Vaccine Antibody Concentrations in Children Exposed to Perfluorinated Compounds

Grandjean P et al. JAMA, Volume 307, Issue 4, January 2012, Pages 391-397. doi:10.1001/jama.2011.2034

A study of children in the Faroe Islands finding that higher blood levels of PFAS were associated with substantially reduced antibody response to childhood vaccines, including diphtheria and tetanus. Children with higher PFAS exposure produced significantly fewer antibodies following vaccination, suggesting that PFAS may impair immune function in ways that reduce vaccine effectiveness. The findings raised serious concerns about the implications of widespread PFAS contamination for public health.

The Dirty Dozen and Clean Fifteen: EWG Shopper's Guide to Pesticides in Produce

Environmental Working Group. Updated annually. 2026 edition.

The Environmental Working Group analyses pesticide residue testing data from the USDA and FDA each year. The 2026 edition analysed 54,344 samples of 47 fruits and vegetables and for the first time highlighted the presence of PFAS pesticides on 63% of all Dirty Dozen produce samples. The most frequently detected pesticide was fludioxonil, a PFAS fungicide. The guide ranks fruits and vegetables by their pesticide load, identifying the twelve crops with the highest residues and the fifteen with the lowest.

Food Colours and Hyperactivity in Children: The McCann Study

McCann D et al. The Lancet, Volume 370, Issue 9598, November 2007, Pages 1560-1567. doi:10.1016/S0140-6736(07)61306-3

A double-blind, randomised, placebo-controlled trial published in The Lancet that found a mixture of six synthetic food colours alongside the preservative sodium benzoate significantly increased hyperactivity in children aged three and eight to nine. The findings led the European Union to require warning labels on foods containing these dyes and prompted the UK Food Standards Agency to recommend their voluntary removal from food products.

Achieving Optical Transparency in Live Animals with Absorbing Molecules

Yao J et al. Science, Volume 385, Issue 6705, July 2024. doi:10.1126/science.adm6742

A study published in Science by researchers at Stanford University that found the common yellow food dye tartrazine, when applied topically to the skin of mice, temporarily rendered tissue translucent. While the study was about optical effects rather than toxicity, it demonstrated the remarkable biological activity of a synthetic food dye and raised broader questions about the interaction of synthetic dyes with biological tissue.

Microplastics in Every Human Placenta Tested

Campen MJ et al. Toxicological Sciences, February 2024. University of New Mexico Health Sciences.

Researchers at the University of New Mexico Health Sciences found microplastics in all 62 human placentas tested. Concentrations ranged from 6.5 to 790 micrograms per gram of placental tissue. The most prevalent polymer was polyethylene, the material used to make plastic bags and bottles, accounting for 54% of the total plastics detected. Lead researcher Matthew Campen expressed concern about steadily rising microplastic volumes in the environment and the potential consequences for mammalian health.

BPA Absorption from Thermal Paper Receipts

Hormann AM et al. PLOS ONE, Volume 9, Issue 10, October 2014. doi:10.1371/journal.pone.0110509

A study demonstrating that BPA is absorbed through the skin from thermal paper receipts, with absorption significantly increased when hands are moist or when hand sanitiser has been applied. Participants handling receipts for five seconds absorbed measurable quantities of BPA, and those using hand sanitiser beforehand absorbed substantially more. The research highlighted a largely overlooked route of BPA exposure that bypasses the digestive system entirely.

Altered Toxicological Endpoints in Humans from Common Quaternary Ammonium Compound Disinfectant Exposure

Hrubec TC et al. Toxicology Reports, Volume 8, 2021, Pages 646-656. doi:10.1016/j.toxrep.2021.03.004

A study finding that quaternary ammonium compounds, found in household cleaning products and fabric softeners, disrupted cholesterol synthesis, decreased mitochondrial function and increased inflammatory markers in human blood samples. A broader body of research by the same group found reduced fertility and neural tube defects in rodents exposed to common quaternary ammonium disinfectants at concentrations comparable to household use. These compounds appear on product labels as ingredients ending in ammonium chloride.

Chemical Sunscreen Absorption and the Case for Mineral Filters

US Food and Drug Administration. FDA Maximum Usage Trials 2019 and 2020. Final order updated June 2026.

FDA Maximum Usage Trials published in 2019 and 2020 found that six commonly used chemical sunscreen filters, oxybenzone, octinoxate, homosalate, octisalate, octocrylene and avobenzone, were absorbed into the bloodstream after a single application at concentrations exceeding the FDA's threshold for potential systemic effects. Oxybenzone was detected at 515 times the FDA's threshold of concern after one weekend of use. All six remain classified as not generally recognised as safe and effective (not GRASE) due to insufficient safety data. In June 2026 the FDA approved bemotrizinol as the first new sunscreen active ingredient in over 25 years, designating it GRASE. Unlike the older chemical filters, bemotrizinol shows low skin absorption and no estrogenic activity in studies. Zinc oxide and titanium dioxide remain the best-evidenced mineral alternatives with the strongest safety and environmental record.

Phthalate Exposure and Sex Steroid Hormones Across the Perimenopausal Period

Babadi RS et al. Environment International, Volume 183, January 2024. doi:10.1016/j.envint.2023.108389

A study examining the relationship between phthalate exposure and sex steroid hormone levels specifically during the perimenopausal transition. Researchers found that higher urinary concentrations of several phthalate metabolites were associated with significant changes in estrogen, progesterone and testosterone levels during perimenopause. Phthalates are present in plastics, fragrance products and many personal care items and are among the most widespread endocrine disrupting chemicals in modern environments. The findings suggest that chemical exposure may influence how women experience the hormonal transition of perimenopause.

Heavy Metals and Earlier Age of Natural Menopause

Fang X, Mahalingaiah S, Schwartz J. Harvard T.H. Chan School of Public Health. Published in Environmental Advances. July 2026. 1,573 postmenopausal women. NHANES data 2003 to 2018.

A study from Harvard T.H. Chan School of Public Health analysing biological samples and survey data from 1,573 postmenopausal women across the United States, examining five heavy metals known or suspected to have hormone-disrupting properties: lead, cadmium, arsenic, mercury and thallium. Using multiple statistical methods including machine learning, the researchers found that women with higher combined exposure to these metals reached natural menopause approximately ten months earlier per quintile increase in exposure. Notably, corrected blood lead ranked as the single strongest contributor to earlier menopause, outranking smoking, income, body weight, number of pregnancies, education level and race and ethnicity. Thallium ranked second and the researchers call for it to be added to the EPA Contaminant Candidate List given its current under-regulation. Experiencing menopause earlier is associated with increased risks of heart disease, osteoporosis, cognitive decline and death from any cause.

Estrogen-Only Hormone Therapy and Mortality in Women Over 65

StatPearls Publishing. Hormone Replacement Therapy review. Updated October 2024.

A review of hormone replacement therapy evidence finding that estrogen-only hormone therapy in women over 65 was associated with a 19% reduction in all-cause mortality and significant reductions in risks for breast cancer, lung cancer, colorectal cancer, congestive heart failure, atrial fibrillation, heart attack and dementia. The review contextualises these findings within the broader evidence base for HRT, noting the significant difference in outcomes between estrogen-only therapy and the combined estrogen and synthetic progestin used in the 2002 Women's Health Initiative study.

Musculoskeletal Symptoms as the Most Prevalent Perimenopause Symptom: A Global Meta-Analysis

Global meta-analysis. Published 2024. Sample size 482,067 women.

A meta-analysis of data from 482,067 women found that joint and muscular discomfort was the most commonly reported symptom of perimenopause, occurring more frequently than hot flashes and night sweats. The finding challenged the widespread assumption that vasomotor symptoms are the primary or most common feature of this transition, and highlighted the extent to which musculoskeletal symptoms have been underresearched and underrecognised in clinical practice.

FDA Removal of Outdated HRT Safety Warnings

US Food and Drug Administration. Announced November 10, 2025. First labelling approvals confirmed June 2026.

On 10 November 2025 the FDA announced it would remove black box warnings on cardiovascular disease, breast cancer and probable dementia from all menopausal hormone therapy products, acknowledging that those warnings were based on outdated interpretations of the 2002 Women's Health Initiative study which overstated risks in older women. Following the announcement, 29 drug companies submitted proposed labelling changes at the FDA's request, and the first batch of six products received approved updated labelling in June 2026. The FDA update was welcomed by menopause specialists who had argued for over two decades that the warnings were causing harm by deterring women from accessing effective treatment. One important nuance: the warning for endometrial cancer on systemic estrogen-only therapy in women who still have a uterus remains in place and was not removed. Women considering HRT are still advised to discuss their individual risk profile with their doctor.

What Predicts Drug-Free Type 2 Diabetes Remission?

Unwin D, Delon C, Unwin J, Tobin S, Taylor R. BMJ Nutrition, Prevention and Health. 2023. doi:10.1136/bmjnph-2022-000544. 186 patients, Norwood Surgery, Southport, UK.

An eight-year observational study from a UK NHS general practice examining 186 patients who followed a lower carbohydrate diet. Overall drug-free type 2 diabetes remission was achieved in 51% of cases. This rose to 77% in those who adopted the approach within one year of diagnosis and dropped to 50% in those who waited more than five years. The practice achieved significant reductions in average weight, HbA1c, LDL cholesterol, triglycerides and blood pressure, while spending the least on diabetes drugs of any practice in the region. Co-authored by Professor Roy Taylor of Newcastle University, whose parallel research identified fat accumulation in the liver and pancreas as the mechanism through which type 2 diabetes develops and can be reversed. The study directly challenges the long-held clinical assumption that type 2 diabetes is a chronic and irreversible condition.

Ultra-Processed Food Consumption and Risk of Diabetes

Welch Center for Prevention, Epidemiology and Clinical Research, Johns Hopkins University. Diabetologia. 2024 Jul 13;67(10):2225-2235. doi:10.1007/s00125-024-06221-5.

A population-based prospective cohort study finding significant associations between ultra-processed food consumption and increased risk of diabetes. Critically for this site, the researchers identified that packaging contaminants found in ultra-processed foods, specifically phthalates, bisphenol A and PFAS, are directly linked to endocrine disruption, inflammation and insulin resistance. The study also found that preservatives such as propionate in breakfast cereals and sausage casings may contribute to insulin resistance by stimulating glucagon release, and that artificial sweeteners including aspartame and sucralose were associated with higher type 2 diabetes risk in both experimental and population studies. This is the study that connects the chemicals covered throughout this site to the metabolic health consequences of ultra-processed food, through one body of peer-reviewed evidence.

The Metabolic Matrix: Re-Engineering Ultra-Processed Foods to Feed the Gut, Protect the Liver and Support the Brain

Harlan TS, Gow RV, Alderson PW, Lustig RH et al. Frontiers in Nutrition. 2023. doi:10.3389/fnut.2023.1098453. Authors include Robert Lustig, UCSF; Rachel Gow, King's College London.

A landmark paper co-authored by Professor Robert Lustig of the University of California San Francisco, one of the world's leading authorities on metabolic disease, alongside researchers from King's College London and George Washington University. The paper describes ultra-processed food as acting as an endocrine disruptor, using that precise phrase in a peer-reviewed context. The authors found that the Standard Western Diet, characterised by ultra-processed foods, drives fat accumulation, reduces mitochondrial efficiency, promotes insulin resistance and alters growth patterns. The paper goes further than most in identifying the mechanisms: ultra-processed foods disrupt the gut microbiome, damage the liver through fructose overload, and interfere with brain satiety signalling. The significance for this site is the direct characterisation of ultra-processed food as an endocrine disruptor, placing it in the same category as the chemical exposures documented throughout this research library.

A NOTE ON HOW WE USE RESEARCH

Science is a process, not a verdict. Where research is contested or where findings have not been fully replicated, we say so. Where the evidence is strong and consistent across multiple independent studies, we say that too. Our aim is never to alarm but to inform accurately, so that the choices you make are based on the best available evidence rather than either industry reassurance or wellness industry exaggeration.