Risk assessment of a Brazilian urban population due to the exposure to pyrethroid insecticides during the COVID-19 pandemic using wastewater-based epidemiology.

Pyrethroids are synthetic insecticides commonly used in agriculture and homes due to their low toxicity to mammals and effectiveness at low doses. However, exposure to pyrethroids can cause various symptoms, depending on the route of exposure. To measure human exposure to pyrethroids, researchers used wastewater-based epidemiology (WBE) with polar organic chemical integrative samplers (POCIS) sampling. This approach is a cost-effective and efficient way to assess exposure to pyrethroids. The study aimed to evaluate the exposure of an urban population in Brazil to pyrethroids during the COVID-19 pandemic using WBE with POCIS sampling. Researchers analyzed 3-phenoxybenzoic acid (3-PBA) in wastewater using passive sampling with POCIS, which was extracted with methanol and analyzed using UPLC-MS/MS. The range of CTWA concentrations of 3-PBA in wastewater was 24.3-298.2 ng L-1, with a mean value of 134 ± 76.5 ng L-1. The values were used to estimate the exposure of the population to pyrethroid insecticides. Three different conversion factors were applied to determine the range of exposure to at least 20 different pyrethroid insecticides. The exposure values ranged from 18.08 to 1441.49 mg day-1 per 1000 inhabitants. The toxicological risk posed to the exposed population was evaluated by calculating the WBE toxicological level (WBE-TL). Lambda-cyhalothrin was used as a reference for risk assessment, and the WBE-TL values for lambda-cyhalothrin ranged from 0.5 to 8.29 (considering the high CF). We compared mobility trends to 3-PBA exposure during the COVID-19 pandemic. The study highlighted the effectiveness of POCIS sampling in WBE and provided useful information for policymakers and regulatory agencies. POCIS sampling has practical advantages, including analyte pre-concentration, low operational cost, and ease of use. Overall, the study shows the importance of monitoring and understanding the exposure of the population to pyrethroid insecticides, especially during the pandemic when people may be spending more time at home.

"Armed to the teeth": The multiple ways to survive insecticidal and predatory challenges in Aedes aegypti larvae.

Environmental pollutants, such as insecticides, can alter the equilibrium of aquatic ecosystems, particularly those closely located to human occupations. The use of such anthropogenic compounds frequently results in the selection of resistant individuals. However, how the underlying insecticide resistance mechanisms interplay with the abilities of the resistant individuals to cope with other environmental challenges (e.g., predators) has not received adequate attention. Here, we evaluated whether resistance to pyrethroid insecticides in larvae of the yellow fever mosquito, Aedes aegypti (Diptera: Culicidae), would affect their abilities to survive other environmental challenges. We assessed the susceptibilities of the pyrethroid-resistant larvae to other insecticides (i.e., the oxadiazine indoxacarb and juvenile hormone mimic pyriproxyfen) and determined the activities of potential detoxification enzymes. Finally, we also recorded potential alterations in larva swimming behavior in the presence of predators, such as the water bug Belostoma anurum (Hemiptera: Belostomatidae). Our results revealed that high pyrethroid resistance was associated with moderate resistance to the other two insecticides. Furthermore, this multiple resistance was associated with higher detoxification activity by glutathione-S-transferases and general esterases. Interestingly, in comparison with insecticide-susceptible larvae, the pyrethroid-resistant larvae not only swam for longer periods and distances, but also took longer to be captured by B. anurum nymphs. Collectively, our findings revealed increased abilities to survive natural environmental challenges (e.g., predatory attacks) in mosquito larvae that express physiological and behavioral changes associated with multiple resistance to insecticides.

In vitro cytotoxicity and genotoxicity of Furia®180 SC (zeta-cypermethrin) and Bulldock 125®SC (ß-cyfluthrin) pyrethroid insecticides in human peripheral blood lymphocytes.

In the present study, human peripheral blood lymphocytes were exposed in vitro to 0, 6, 12, 18, 24, and 30 µg/mL Furia®180 SC (zeta-cypermethrin) and 0, 6.3, 12.5, 18.8, 25, and 31.3 µg/mL Bulldock®125 SC (ß-cyfluthrin). Exposure to 32 µg/mL bleomycin for 24 h served as a positive control. The cytotoxic and genotoxic effects of each insecticide were analyzed using alkaline comet and trypan blue dye exclusion assays. DNA damage was evaluated through three genotoxicity parameters: tail length (TL), tail moment (TM) and tail intensity (TI). Furia®180 SC and Bulldock®125 SC pyrethroid insecticides and bleomycin significantly increased DNA damage in a concentration-dependent manner. Bulldock®125 SC induced more DNA damage than Furia. Lymphocyte viability did not change after exposure to different concentrations of the two pyrethroid insecticides and bleomycin. Moreover, genotoxic results demonstrated that Furia®180 SC and Bulldock®125 SC insecticides caused in vitro DNA damage in human peripheral lymphocytes.

Analysing deltamethrin susceptibility and pyrethroid esterase activity variations in sylvatic and domestic Triatoma infestans at the embryonic stage

The aim of the present work was to study the deltamethrin susceptibility of eggs from Triatoma infestans populations and the contribution of pyrethroid esterases to deltamethrin degradation. Insects were collected from sylvatic areas, including Veinte de Octubre and Kirus-Mayu (Bolivia) and from domiciliary areas, including El Palmar (Bolivia) and La Pista (Argentina). Deltamethrin susceptibility was determined by dose-response bioassays. Serial dilutions of deltamethrin (0.0005-1 mg/mL) were topically applied to 12-day-old eggs. Samples from El Palmar had the highest lethal dose ratio (LDR) value (44.90) compared to the susceptible reference strain (NFS), whereas the Veinte de Octubre samples had the lowest value (0.50). Pyrethroid esterases were evaluated using 7-coumaryl permethrate (7-CP) on individually homogenised eggs from each population and from NFS. The El Palmar and La Pista samples contained 40.11 and 36.64 pmol/min/mg protein, respectively, and these values were statistically similar to NFS (34.92 pmol/min/mg protein) and different from Kirus-Mayu and Veinte de Octubre (27.49 and 22.69 pmol/min/mg protein, respectively). The toxicological data indicate that the domestic populations were resistant to deltamethrin, but no statistical contribution of 7-CP esterases was observed. The sylvatic populations had similar LDR values to NFS, but lower 7-CP esterase activities. Moreover, this is the first study of the pyrethroid esterases on T. infestans eggs employing a specific substrate (7-CP).

Toxicity of non-pyrethroid insecticides against Triatoma infestans (Hemiptera: Reduviidae)

Triatoma infestans (Klug) is the main vector of Chagas disease, which is a public health concern in most Latin American countries. The prevention of Chagas disease is based on the chemical control of the vector using pyrethroid insecticides. In the last decade, different levels of deltamethrin resistance have been detected in certain areas of Argentina and Bolivia. Because of this, alternative non-pyrethroid insecticides from different chemical groups were evaluated against two T. infestans populations, NFS and El Malá, with the objective of finding new insecticides to control resistant insect populations. Toxicity to different insecticides was evaluated in a deltamethrin-susceptible and a deltamethrin-resistant population. Topical application of the insecticides fenitrothion and imidacloprid to first nymphs had lethal effects on both populations, producing 50% lethal dose (LD50) values that ranged from 5.2-28 ng/insect. However, amitraz, flubendiamide, ivermectin, indoxacarb and spinosad showed no insecticidal activity in first instars at the applied doses (LD50 > 200 ng/insect). Fenitrothion and imidacloprid were effective against both deltamethrin-susceptible and deltamethrin-resistant populations of T. infestans. Therefore, they may be considered alternative non-pyrethroid insecticides for the control of Chagas disease.

Evaluation of different Cypermethrin formulations and concentrations in the control of Musca domestica

Cypermethrin (4 g/l, 5 g/l wettable powder and 7 ml/l, 10 ml/l emulsifiable concentrate) was tested, under laboratory conditions, against the adult Musca domestica. As a standard for comparison, a 6 ml/l concentrate suspension formulation of deltamethrin was used. One and twenty-four hours after application, mortality counts showed that the substances under test killed, respectively, more than 80% and 85% of the exposed insects. Under the conditions of the test, cypermethrin was considered effective in the control of the house fly.