The ASCLEPIOS project, a European research group studying chemical exposure and sperm quality, followed 248 Danish farmers over an entire agricultural spraying season. About half regularly sprayed pesticides; the rest farmed without using them. Both groups provided two semen samples — one before and one after the spraying period.

Both groups experienced similar declines in sperm concentration from the first sample to the second. When the researchers compared the two groups directly, after adjusting for factors like smoking, alcohol, and abstinence time, there was no statistically meaningful difference in how sperm concentration, motility, shape, or chromosomal integrity changed between pesticide users and non-users. The authors concluded that pesticide use by Danish farmers was not a likely cause of short-term changes in semen quality or reproductive hormone levels.

Researchers at the University of Tokyo recruited 322 male university students in Metropolitan Tokyo — a general population sample, not men seeking fertility treatment — and measured pyrethroid insecticide exposure through a urine breakdown product called 3-phenoxybenzoic acid (3-PBA). Pyrethroids are among the most widely used insecticides in homes, agriculture, and mosquito control worldwide.

Detectable 3-PBA was found in 91% of the young men, confirming widespread everyday exposure. However, when researchers ran statistical models to test whether 3-PBA levels predicted sperm concentration, motility, morphology, or any other semen parameter, 3-PBA was not selected as a significant factor in any model. Average sperm concentration was 56 million per milliliter and motility was 61%, both within normal ranges. The authors concluded that environmental pyrethroid exposure at levels found in the general population did not affect semen quality.

INSERM, France''s national health research institute, studied 42 banana plantation workers in Guadeloupe who had documented blood levels of chlordecone — a pesticide banned in the 1970s that persists in Caribbean soils — and compared them to 45 men working outside agriculture. Chlordecone is a known endocrine disruptor, meaning it interferes with hormones.

Despite detecting chlordecone in the blood of 88% of all men tested, including non-agricultural workers, the researchers found no significant differences in any semen characteristic between the higher-exposure plantation workers and the lower-exposure controls: sperm volume, concentration, output, motility, and shape were all statistically equivalent. Hormone levels including FSH, LH, testosterone, inhibin B, and estradiol were also not significantly different. Blood chlordecone concentration was not meaningfully correlated with any single semen or hormone measurement.

The same 2023 meta-analysis by Perry and colleagues at George Mason University (published in Environmental Health Perspectives) that found a meaningful effect in occupational settings also separately analyzed studies of men with only general environmental pesticide exposure — such as living near farms or consuming pesticide residues in food — rather than directly handling pesticides at work.

For this environmental exposure subgroup, the pooled effect on sperm concentration was essentially zero (Hedges g = −0.03), compared to −0.43 for occupational exposure. This 14-fold difference between occupational and environmental exposure groups strongly indicates that the harm seen in agricultural workers is tied to the high doses involved in direct pesticide handling, not to the low-level exposure experienced by the general public. People who are not applying pesticides as part of their work appear to face little to no measurable sperm quality impact.

Researchers at multiple European institutions published a study in Scientific Reports examining how Roundup Ultra Plus — the world''s best-selling herbicide formulation — affects mammalian sperm. They tested pure glyphosate (the active ingredient) and the surfactant chemical POEA (a major ingredient added to commercial Roundup) separately, as well as the combined product.

Pure glyphosate at concentrations up to 10 times the equivalent found in Roundup caused no measurable change in any sperm parameter. However, Roundup Ultra Plus at 0.01% concentration did affect sperm, and testing POEA alone at an equivalent concentration produced the same effects — meaning the surfactant was entirely responsible for the sperm harm, not the pesticide itself. The researchers also reviewed two multi-generation animal studies with glyphosate that found no effects on fertility or reproductive outcomes.

The European Food Safety Authority (EFSA) conducted a comprehensive peer review of glyphosate in 2023 as part of the EU''s decision on whether to renew the pesticide''s approval. The review examined all available animal, cell-based, and epidemiological studies for signs that glyphosate damages reproduction or child development.

EFSA concluded that no critical areas of concern were identified for reproductive or developmental toxicity. The European Chemicals Agency''s Committee for Risk Assessment separately reached the same conclusion: glyphosate did not meet the scientific criteria for classification as a substance harmful to reproduction. Based in part on these findings, the EU renewed glyphosate''s approval in November 2023. Researchers who disagree with these conclusions argue that regulatory reviews depend on industry-submitted data and may not capture all risks, but under current scientific and regulatory standards, glyphosate is not classified as a reproductive hazard.

A Navigation Guide systematic review — a rigorous method that rates both evidence quality and confidence — was conducted by researchers at George Mason University and international collaborators. It identified 19 studies across 14 countries examining whether pesticide exposure lowered sperm quality in humans.

Of those 19 studies, only 15 (79%) found any significant association with worse semen quality, while 4 (21%) did not. When broken down by specific sperm measures, the inconsistency was even more pronounced: only 42% of studies found a significant decrease in sperm concentration, and only 36% found significant changes in sperm shape. The reviewers rated the evidence for sperm concentration as "limited" and for sperm shape as "inadequate" — not strong enough for firm causal conclusions. The high inconsistency across studies was noted as a major gap in the evidence.

Researchers at Radboud University Nijmegen in the Netherlands studied 398 women working in greenhouses — a high-pesticide environment — and compared their time-to-pregnancy to 524 women in non-agricultural work. Time-to-pregnancy is a standard measure of fertility: the longer it takes to conceive, the lower the couple''s fertility.

Before adjusting for other factors, the greenhouse workers appeared to get pregnant slightly faster (fecundability ratio 1.18), which the researchers attributed to differences in age and socioeconomic background. After adjusting for confounders, the difference became non-significant (FR 1.11, not statistically meaningful). When the analysis was restricted to full-time workers or first pregnancies only, the adjusted results showed no significant fertility difference between the exposed and unexposed groups (FR 0.89 and 0.90 respectively). The study concluded that the evidence for pesticide-related fertility harm in this population was weak.

Researchers at Exponent Inc. and academic collaborators published a systematic review in Birth Defects Research Part B examining the entire published epidemiological literature on atrazine — the most commonly detected pesticide in U.S. water supplies — and adverse pregnancy outcomes including miscarriage, preterm birth, and birth defects.

The review found that the quality of the epidemiological data was poor overall, with most papers relying on geographic or aggregate exposure estimates rather than individual measurements. Across all outcome categories studied, none showed consistent positive associations across multiple independent studies. A large Canadian farm study found no significant link between atrazine use and miscarriage. The authors concluded that the available evidence does not support a causal connection between atrazine exposure and adverse pregnancy outcomes, and that better-designed studies with individual biomonitoring are needed before firm conclusions can be drawn.