A nationwide survey of four diamide insecticides (DAIs) across 47 Chinese cities and nine major river basins has revealed widespread contamination, with cyantraniliprole (CYTP) the most abundant compound and broflanilide (BFA) the most concerning for benthic midges. The study, published in Environmental Chemistry and Ecotoxicology, provides the first nationwide snapshot of these newer pesticides in Chinese surface waters, filling a critical data gap as DAIs replace older, broader-spectrum insecticides.
DAIs are increasingly favored in agriculture because of their improved selectivity, but their environmental footprint has remained largely uncharacterized. The researchers detected all four compounds at concentrations ranging from below detection to 119 ng/L, with a national median total concentration of 40 ng/L. CYTP was found at every sampling site, with a median of 17 ng/L, and dominated in southern basins, while BFA contributed more in northern basins. The regional patterns tracked local crop-planting and pesticide-use practices, rather than land-use or meteorological factors, suggesting that agricultural choices drive contamination signatures.
The most striking finding was a mismatch between concentration and ecological risk. Although BFA was not the most abundant pollutant, it became the primary screening-level driver for the benthic midge Chironomus dilutus because its species-specific chronic effect threshold is much lower. BFA screening risk quotients exceeded 1 at 22% of sampling sites. For Daphnia magna, the combined risk of the four DAIs surpassed the medium-risk threshold at 22% of sites, while cumulative risks for fish and aquatic plants remained negligible in this screening framework.
The study also modeled a conservative scenario of direct ingestion of untreated surface water. Children aged 0–6 years had a 95th-percentile cumulative daily intake of 9.1 ng/kg body weight/day, about 2.4 times the adult value of 3.7 ng/kg body weight/day. Although all hazard quotients remained below 1, the higher exposure for children underscores the need for additional attention to sensitive groups.
These results carry significant implications for environmental monitoring and regulation. They demonstrate that concentration alone cannot fully capture risk; toxicity data that account for compound- and species-specific effects are essential. As DAIs become more prevalent, monitoring programs should integrate nationwide occurrence data with chronic toxicity thresholds to identify hotspots and protect vulnerable ecosystems. The findings also highlight the importance of considering children's exposure in risk assessments, even when hazard quotients suggest no immediate concern. With DAIs detected in rivers across dozens of cities, the study calls for sustained surveillance and targeted management to prevent future ecological damage.
