Researchers at UC Berkeley and the California Department of Public Health examined 114 male workers at plants that produced dibromochloropropane (DBCP), a soil fumigant pesticide used widely in farming. Among the 25 men who had not had vasectomies, 14 had either no sperm at all or severe sperm deficiency.

Across all workers screened, 13.1% were completely without sperm (azoospermic) and 16.8% had severely low counts. Blood hormone tests showed the testes themselves were failing, not just blocked tubes: the hormones that signal the testes to produce sperm (FSH and LH) were elevated, while sperm output was near zero. The damage correlated with how long a man had worked with DBCP, pointing directly at the chemical as the cause.

Researchers analyzed data from the largest documented occupational male infertility case in history, involving male banana and pineapple plantation workers from 12 countries including the Philippines, Costa Rica, and Honduras. All had been exposed to DBCP, a pesticide used to kill soil worms in tropical plantations before it was banned in the late 1970s.

Of all men studied, 64.3% were found to be either completely without sperm or severely sperm-deficient. In the Philippine subset alone, 90.1% had azoospermia or severe oligospermia. On average, these men had 2.5 children, but 28.5% of them had fathered no children at all — a far higher childlessness rate than the general population. The scale and consistency of findings across 12 countries made this one of the clearest demonstrations of a pesticide directly destroying male fertility.

Melissa Perry and colleagues at George Mason University, funded by the U.S. National Institute of Environmental Health Sciences, pooled data from 20 studies across 21 populations and 1,774 adult men. The analysis examined organophosphate and carbamate insecticides — two of the most widely used pesticide classes in global agriculture.

The overall pooled result was a statistically significant reduction in sperm concentration among exposed men (Hedges g = −0.30, meaning about one-third of a standard deviation below unexposed men). The effect was much stronger among men with direct occupational exposure such as farmers and pesticide applicators (g = −0.43) compared to men with general environmental exposure (g = −0.03). The findings, published in Environmental Health Perspectives, suggest that direct handling of these pesticides poses a meaningful risk to male fertility.

An international meta-analysis published in Frontiers in Endocrinology pooled nine studies from China, Japan, Peru, France, Mexico, Malaysia, Venezuela, and Iran. In total, 349 exposed men were compared with 417 unexposed controls across multiple semen quality measures.

Sperm concentration in exposed men was about half a standard deviation lower than in controls (standardized mean difference −0.50). Total sperm motility (how many sperm move) was also about half a standard deviation lower (−0.50), as was the share of sperm with normal shape (−0.49). All three differences were statistically significant. Notably, testosterone and other hormones were not significantly different between groups, suggesting the pesticides were interfering directly with sperm production rather than through the hormonal system.

Researchers at Harvard T.H. Chan School of Public Health followed 325 women through 541 IVF treatment cycles between 2007 and 2016. Women reported how much of each type of fruit and vegetable they ate, and researchers classified produce by whether it typically carries high or low pesticide residues using U.S. Department of Agriculture testing data.

Women eating the most high-pesticide produce (two or more servings per day) had a 26% lower chance of a live birth compared to women eating the least (39% vs. 65% live birth rate). Their chance of a clinical pregnancy was 18% lower. Replacing just one daily serving of high-pesticide produce with a low-pesticide alternative was associated with 88% higher odds of a live birth and 79% higher odds of clinical pregnancy. The findings were published in JAMA Internal Medicine.

Environmental Health Perspectives published research led by Shanna Swan using data from Missouri men recruited through fertility clinics, comparing them to men from two comparison cities. Pesticide exposure was measured through blood and urine samples rather than self-reported occupation, making the results more reliable.

Men in Missouri with the highest measured levels of alachlor — a widely used corn and soybean herbicide — were 30 times more likely to have low sperm quality than men with no detectable alachlor. Men with the highest levels of atrazine, the most commonly detected pesticide in U.S. waterways, were 11.3 times more likely to have poor sperm quality. High diazinon (an organophosphate insecticide) metabolite levels produced a 16.7-fold increase in risk. These associations were specific to men in the agricultural region and were not replicated in the non-agricultural comparison cities, strengthening the case that the pesticides themselves were responsible.

Researchers at Universidad Peruana Cayetano Heredia recruited 31 men who worked directly applying organophosphate pesticides and 31 matched control men with no pesticide exposure. Exposure was verified through measuring six organophosphate breakdown products in urine using gas chromatography, not just through occupation records.

The pesticide-exposed men showed significantly worse results across multiple fertility markers: their semen volume was lower, fewer of their sperm were moving (lower motility), and fewer had normal shapes. Blood testosterone and the hormone LH, which signals the testes to produce testosterone, were both significantly lower in the exposed group. The immature-sperm percentage and white blood cell count in semen were higher — both signs of reduced reproductive health. The findings were published in the journal Environmental Health.

Tyrone Hayes and colleagues at the University of California, Berkeley, raised 40 male African clawed frogs from birth in water containing 2.5 parts per billion of atrazine — a concentration lower than the U.S. EPA''s safety limit for drinking water. At the end of the study, published in the Proceedings of the National Academy of Sciences, the researchers found severe reproductive harm.

Four of the 40 genetically male frogs (10%) had completely changed sex: they became functional females, mated with normal males, and produced viable eggs. Among the other 36, nearly all showed signs of reproductive damage including depressed testosterone, reduced sperm production, shrunken breeding glands, and suppressed mating behavior, leading to fewer offspring. Effects were observed at concentrations as low as 0.1 parts per billion. Although this was a wildlife study, the results are widely used in evaluating whether atrazine poses a reproductive risk to mammals and humans.

The Minnesota Department of Health studied farm families in the Red River Valley, one of the most intensively farmed regions in the U.S. Researchers surveyed spouses of pesticide applicators about their pregnancy histories and pesticide contact, then compared their miscarriage rates to the general population.

Wives of men who applied fungicides had a 1.6- to 2-fold elevated risk of miscarriage and fetal loss compared to women with no such exposure in the household. Women who directly applied pesticides themselves had 1.8 times the risk of miscarriage. The fact that non-applying spouses also showed elevated risk suggested the damage may have been partly caused by pesticide-harmed sperm from the father (a pathway called male-mediated reproductive toxicity). The results were published in the American Journal of Industrial Medicine.

Researchers at the Universidad Autónoma de Coahuila in Mexico recruited 52 male farmworkers and collected 139 semen samples from them across the agricultural spraying season, capturing changes over time. Pesticide exposure was measured using gas-liquid chromatography to detect organophosphate breakdown products in urine, giving a direct chemical measure rather than relying on questionnaires.

Workers with the highest pesticide exposure showed a significant decrease in total sperm count compared to both the low-exposure and non-exposed groups. The effect was dose-dependent: the higher the measured pesticide metabolite levels, the worse the sperm count. Sperm concentration also varied with season, rising after the spraying season ended — suggesting the damage was reversible with reduced exposure. The study was published in the journal Toxicological and Environmental Chemistry.