{"id":38413,"date":"2025-05-08T00:01:17","date_gmt":"2025-05-08T04:01:17","guid":{"rendered":"https:\/\/beyondpesticides.org\/dailynewsblog\/?p=38413"},"modified":"2025-05-06T12:43:28","modified_gmt":"2025-05-06T16:43:28","slug":"neonicotinoid-exposure-threatens-fish-health-highlighting-cascading-effects-to-humans-as-consumers","status":"publish","type":"post","link":"https:\/\/beyondpesticides.org\/dailynewsblog\/2025\/05\/neonicotinoid-exposure-threatens-fish-health-highlighting-cascading-effects-to-humans-as-consumers\/","title":{"rendered":"Neonicotinoid Exposure Threatens Fish Health, Highlighting Cascading Effects to Humans as Consumers"},"content":{"rendered":"

(Beyond Pesticides<\/em>, May 8, 2025) A study, published in Environmental Pollutants and Bioavailability<\/em><\/a>, assesses the impacts on Nile tilapia (Oreochromis niloticus<\/em>) with subacute and chronic exposure to thiamethoxam<\/a>, a neonicotinoid<\/a> insecticide, and finds genotoxicity, oxidative stress<\/a>, and changes in tissue structure, among other threats to organ function and overall fish health. \u201cThe study focused on biochemical markers, genetic damage, pesticide residue levels in fish flesh, and histopathological changes in fish exposed to different concentrations of thiamethoxam<\/a>,\u201d the authors state. The threats do not end there; human health is also at risk from the consumption of these contaminated fish.<\/p>\n

\u201cUnfortunately, neonicotinoids, rapidly washed into surface water<\/a> from agricultural areas, pose a significant threat to environmental water quality and can harm non-target species, particularly aquatic organisms<\/a>,\u201d the researchers state. The accumulation of these chemicals leads to \u201cultimately harming both aquatic ecosystems and human health<\/a>,\u201d they say.<\/p>\n

In particular, the study highlights that prolonged exposure to high doses of thiamethoxam can cause \u201csignificant negative effects on fish health,\u201d the authors note. They continue: \u201cThis exposure led to increased levels of urea and ALT [alanine aminotransferase] in the blood, indicating potential damage to the kidneys and liver<\/a>. Additionally, thiamethoxam caused oxidative stress, as evidenced by elevated levels of MDA [malondialdehyde, a product of lipid peroxidation] and upregulated TLR2 [toll-like receptor 2] gene expression.\u201d<\/p>\n

Residues of thiamethoxam in Nile tilapia muscle correlate with increasing exposure and elevated urea levels. Even lower thiamethoxam concentrations are associated with subsequent kidney dysfunction. \u201cThiamethoxam also negatively impacted the fish\u2019s antioxidant defense system,\u201d the researchers say. \u201cIt significantly reduced the expression of key antioxidant genes like ghrelin and catalase [CAT],\u201d they note, which \u201ccould be a consequence of thiamethoxam-induced gastroenteritis\u201d and indicative of damage to gut cells.<\/p>\n

Lastly, the authors share, \u201cHistological examination revealed severe degenerative changes in the gills and liver tissues of the fish exposed to thiamethoxam, with the severity of the damage increasing with the concentration of the pesticide.\u201d These results are concerning, as chemicals such as thiamethoxam are able to bioaccumulate and biomagnify<\/a> within the food chain, leading to impacts on various organisms, including humans.<\/p>\n

The study, carried out in Egypt, utilizes 200 Nile tilapia within one control group and four test groups exposed to multiple concentrations of thiamethoxam for varying lengths of time. \u201cPrior to the main study, preliminary trials were conducted to establish non-lethal thiamethoxam concentrations, which were subsequently used as sublethal doses in toxicity assessments,\u201d the researchers say.<\/p>\n

In analyzing biochemical markers, this study determines pesticide toxicity. \u201cSpecifically, this study examined the impact of thiamethoxam on serum liver and kidney biochemical functions, oxidative stress markers (SOD [superoxide dismutase], MDA, and TAC [total antioxidant capacity]), gene expression (TLR2, ghrelin, and catalase), tissue residue levels, and histopathological changes in the gills and liver of fish,\u201d the authors explain.<\/p>\n

The results show a reduction in both SOD and TAC biomarkers. \u201cCollectively, these findings provide compelling evidence that TMX [sublethal exposure to thiamethoxam] exposure induces significant oxidative stress in Nile tilapia, characterized by diminished antioxidant enzyme activity, increased lipid peroxidation, and compromised overall antioxidant capacity,\u201d the researchers note. Additional results, including the significantly elevated creatinine levels, also indicate potential renal dysfunction, as well as impacts on hepatic gene expression \u201cassociated with growth (ghrelin), immunity (TLR2), and oxidative stress (CAT).\u201d<\/p>\n

\u201cThe analysis revealed significant, concentration-dependent alterations in the expression of these genes across all treatment groups compared to the control,\u201d the authors say. They continue: \u201cNotably, ghrelin expression demonstrated a significant downregulation… indicative of potential growth inhibition. Conversely, TLR2 expression exhibited a substantial upregulation…suggesting a pronounced activation of the immune response. Furthermore, CAT gene expression displayed a significant downregulation… signifying heightened oxidative stress.\u201d These results highlight thiamethoxam\u2019s ability to disrupt physiological pathways in fish species by compromising growth, immune function, and the management of oxidative stress.<\/p>\n

Lastly, the fish exposed to different concentrations of thiamethoxam all show a range of impacts and damage to their gills. From inflammation and hemorrhaging to exacerbated gill lesions, even the lower concentrations yielded concerning results. As the concentrations increase, more severe hepatic pathologies are induced. The researchers note necrosis (cell death) within tissues and congestion of hepatic blood vessels at the higher exposure levels.<\/p>\n

\u201cThese findings demonstrate a clear concentration-dependent increase in histopathological damage to the gills and liver of Nile tilapia following [thiamethoxam] exposure, indicative of significant toxicological effects,\u201d the authors write. \u201cThe histopathological findings support the biochemical results, showing direct damage to gill and liver tissues caused by thiamethoxam.\u201d<\/p>\n

Previous research confirms these results, within Nile tilapia and similar species, to both thiamethoxam and other neonicotinoids. Important study results include:<\/p>\n