A nationwide survey of four diamide insecticides (DAIs) across 47 Chinese cities and nine major river basins has found widespread contamination, with cyantraniliprole (CYTP) the most abundant compound but broflanilide (BFA) raising the greatest screening-level concern for benthic midges. The findings, published in Environmental Chemistry and Ecotoxicology, highlight that environmental concentration alone may not reflect ecological risk, as compound- and species-specific toxicity can shift the driver of concern.
Researchers detected the four DAIs at concentrations ranging from below the detection limit to 119 ng/L, with a national median total concentration of 40 ng/L. CYTP was found at every sampling site, with a median concentration of 17 ng/L, and contributed most in southern basins, while BFA made a larger contribution in northern basins. According to corresponding author Yanhao Zhang, local crop-planting patterns and crop-specific pesticide use likely shaped these regional pollution signatures, whereas land-use and meteorological variables could not explain the nationwide distribution.
The study’s most significant implication is the mismatch between concentration and ecological risk. Although BFA was not the most abundant pollutant, it became the main screening-level driver for the benthic midge Chironomus dilutus because its species-specific chronic effect threshold was much lower. BFA screening risk quotients exceeded 1 at 22% of sampling sites. For Daphnia magna, the combined risk of the four DAIs exceeded the medium-risk threshold at 22% of sites, while cumulative risks for fish and aquatic plants remained negligible in the screening framework. These results suggest that monitoring programs relying solely on concentration data could overlook risks to sensitive benthic organisms.
The study also modeled a conservative scenario of direct ingestion of untreated surface water. The 95th-percentile cumulative daily intake for children aged 0–6 years was 9.1 ng/kg body weight per day, about 2.4 times the adult value of 3.7 ng/kg body weight per day. Although all hazard quotients remained below 1, the elevated exposure for children indicates that sensitive groups warrant additional attention in risk assessments. The spatial exposure pattern also showed regional tendencies consistent with crop-use patterns.
Zhang emphasizes that the findings call for a more integrated approach. “Our results showed that environmental concentration alone could not tell the whole risk story,” Zhang says. “Monitoring should combine nationwide occurrence data with compound- and species-specific toxicity, while giving additional attention to sensitive groups such as children.” The full study provides a baseline for future regulatory and monitoring efforts as DAIs replace older pesticides with improved selectivity but potentially underappreciated ecological footprints.
