Research and Studies

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The 50% Sperm Count Decline (Levine et al., 2017)

The Accelerating Decline (Levine et al., 2022)

Atrazine and Frog Feminisation (Hayes et al., 2010)

Microplastics in Human Placentas (Campen et al., 2024)

PFAS in UK Water Supplies (UK Government, 2026)

The Dirty Dozen and Clean Fifteen (EWG, 2026)

Chemical Sunscreen Absorption (FDA, 2019)

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. No significant decline was observed in South America, Asia and Africa, though the authors note far fewer studies have been conducted in those regions.

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 compared to the period before. The study found significant declines across all continents studied, suggesting the problem is now genuinely global rather than limited to Western countries.

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, one of the most widely used herbicides in the world, caused complete feminisation in male African clawed frogs, with some males developing fully functional female reproductive organs capable of producing eggs. The exposures occurred 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, EPA-sponsored replication attempts did not fully replicate the findings, and the scientific debate around atrazine's effects in amphibians remains active. In humans, atrazine has been associated with reduced testosterone and sperm motility in occupationally exposed populations, though research is ongoing. Atrazine is banned in the European Union but continues to be widely used in the United States.

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 used a new analytical tool to measure microplastics in human placentas, finding them in all 62 samples tested. Concentrations ranged from 6.5 to 790 micrograms per gram of placental tissue. The most prevalent polymer found was polyethylene, the material used to make plastic bags and bottles, accounting for 54% of the total plastics detected. PVC and nylon each represented approximately 10% of the remainder.

Lead researcher Matthew Campen noted that the health effects of these concentrations are not yet fully understood, but expressed concern about a steadily rising volume of microplastics in the environment and the potential consequences for all mammalian life. An earlier 2020 Italian study published in Environment International was the first to detect microplastics in human placenta, finding fragments in four out of six samples examined.

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, published in February 2026, 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, managing and ultimately reducing PFAS contamination across the environment, food chain and consumer products, though campaigners noted the plan contains no binding reduction targets or specific timelines.

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 United States Department of Agriculture and the Food and Drug Administration each year to produce its Shopper's Guide to Pesticides in Produce. The guide ranks fruits and vegetables by their pesticide load, identifying the twelve crops with the highest residues, the Dirty Dozen, and the fifteen with the lowest, the Clean Fifteen. While the testing is conducted on US produce, the underlying pesticide use patterns and residue profiles are broadly comparable to those found in UK grown and imported produce.

The EWG's methodology has been independently reviewed and its findings are broadly consistent with UK Pesticide Residue Committee annual testing data, which similarly finds the highest residue levels on soft fruits, leafy greens and thin-skinned vegetables.

Sunscreen Drug Products for Over-the-Counter Human Use: Proposed Rule

US Food and Drug Administration. Federal Register, February 2019.

The FDA's 2019 proposed rule on sunscreen safety determined that only two active ingredients, zinc oxide and titanium dioxide, can currently be considered generally recognised as safe and effective based on the available evidence. The FDA found that twelve other commonly used chemical sunscreen filters, including oxybenzone, octinoxate and homosalate, were absorbed into the bloodstream at concentrations exceeding the FDA's threshold for potential systemic effects after just a single application. This does not mean these ingredients are unsafe, but the FDA determined that more safety data is needed before they can be confirmed as safe for widespread daily use.

A subsequent 2020 FDA study confirmed that chemical sunscreen filters including oxybenzone reached blood concentrations far exceeding the threshold of concern after four days of normal use, and that concentrations continued to rise with continued application. The FDA has called for further safety studies from manufacturers.

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.