Impact of pesticides lambda-cyhalothrin, emamectin benzoate, and thiophanate-methyl used alone and in mixtures on reproduction and oxidative stress markers in male Wistar rats

Pesticide exposure is a growing public health concern, particularly in agricultural regions where workers and communities encounter multiple chemical compounds simultaneously. Although previous studies have investigated the reproductive toxicity of individual pesticides, the combined effects of commonly co-applied insecticide–fungicide mixtures remain poorly characterized. We hypothesized that the simultaneous administration of lambda-cyhalothrin, emamectin benzoate, and thiophanate-methyl, three pesticides routinely co-applied in eastern Algerian agriculture, would exert synergistic reproductive toxicity in male rats, exceeding the effects observed with each compound alone. Seventy-two adult male Wistar rats (n = 8 per group) were treated by oral gavage for 6 weeks with each pesticide at 1/20 LD ₅₀ (high dose) or 1/60 LD ₅₀ (low dose), or with a ternary mixture at the same dose levels; one group served as the control. Testicular and epididymal weights, plasma testosterone concentration, sperm parameters (concentration, motility, and speed), oxidative stress markers (GSH, GPx, and MDA), and tissue histopathology were evaluated. All three pesticides at the high dose significantly impaired reproductive parameters and induced oxidative stress; however, the mixture group (G8, 1/20 LD ₅₀ ) exhibited the most pronounced alterations, including a highly significant decrease in testicular weight, severe testosterone suppression, marked sperm parameter decline, and extensive histopathological damage consistent with synergistic toxicity. These findings provide the first evidence that the combination of lambda-cyhalothrin, emamectin benzoate, and thiophanate-methyl produces synergistic reproductive toxicity in male rats, underscoring the need for mixture-based risk assessment in agricultural pesticide regulation.