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Mixtures Effects

also see insectsbirds fungicides, mixture effectsdigestive tract/microbiome, Bee Die-off, microbiota changes,  filed under organochlorines, health/low dose

Study of Chemical Mixtures at Low Concentrations Again Finds Adverse Health Effects   (Beyond Pesticides, April 10, 2024) Researchers in a 2024 Chemosphere study find synergistic relationships in certain chemical mixtures, particularly heptachlor and triallate and trifluralin and lindane at lower concentrations, respectively.... “According to a Centers for Disease Control (CDC) assessment, more than 50 pesticides are detected in blood or urine samples from the US population,” Researchers point to a cause for concern.... Researchers “used the exposure data from a complex operating site with legacy pesticide pollution.... “Only volatile COPCs... in soil and groundwater were included in this study (triallatetrifluralinlindaneheptachlordieldrin, and aldrin,” the researchers indicate in the Methods section. Quantitative risk assessment for pesticide exposure was rooted on oral exposure... which demands a higher dose to induce an identifiable adverse effect relative to inhalation exposure. In other words, using an oral reference dose may underestimate the potential risk....  Researchers did find values suggesting “significant health concerns” to toddlers, infants, teenagers, and adults in “commercial and industrial land use.”... “Nine of the 15 tested binary mixtures of pesticides synergistically reduced cell viability. Seven mixtures (Trifluralin/Heptachlor, Trifluralin/Aldrin, Lindane/Heptachlor, Lindane/Aldrin, Heptachlor/Dieldrin, Heptachlor/Aldrin and Dieldrin/Aldrin) were synergistic at higher concentrations. However, two mixtures of herbicides and OCPs (organochlorine pesticides) (Trifluralin/Lindane and Triallate/Heptachlor) interacted synergistically at lower concentrations'.    SNAP Comment: All the pesticides listed were historically registered in Canada except dieldrin and two still are:trifluralin and triallate. 'There are 23,078 federal sites listed in the FCSI maintained by the Treasury Board of Canada Secretariat, including 5,337 active contaminated sites and 2,355 suspected sites. 15,386 are listed as closed because remediation is complete or because no action was necessary following assessment.' Inventory of federal contaminated sites.    'Research shows adverse health effects most likely occur within a 1.8 mile boundary around a Superfund site.' Millions of Americans Live Near Toxic Waste Sites. How Does This Affect Their Health?(February 16, 2022)

Neonicotinoids Combined with Other Pesticides Elevate Hazards to Honey Bee  (Beyond Pesticides, February 22, 2023)   'Among the eight pesticides tested, honey bee toxicity was as follows from most to least toxic: the neonicotinoid insecticide thiamethoxam, the organophosphate insecticide dimethoate, the carbamate insecticide methomyl, the synthetic pyrethroid insecticides permethrin, and then cypermethrin, the triazole fungicide tetraconazole, and the synthetic pyrethroids cyfluthrin and then esfenvalerateThese results did change based on different treatment lengths, yet thiamethoxam was found to remain the most toxic throughout all studies.  In the study, scientists evaluate a total of 98 different mixtures, from binary combinations of two different chemicals to octonary combinations of all eight different pesticides. Within these tests, approximately 30% of these were found to be synergistic to honey bees, exhibiting toxicity greater than each individual material in the mixture.  Perhaps the most concerning interaction came from combinations that included thiamethoxam and the fungicide tetraconazole. Any variation of pesticide combinations that include these two chemicals have a roughly 55% chance of exhibiting synergistic toxicity to honey bees.'

Pesticide Mixtures Reduce Life Span of Honey Bees, Damage Gut Microbiome    (Beyond Pesticides, November 1, 2022) Study done with field relevant concentrations. 'Honey bees exposed to a combination of multiple pesticides suffer a reduced lifespan and experience adverse changes to their gut microbiome, increasing susceptibility to pathogens and disease. This finding comes from a study published recently in Science of the Total Environment, which examines the interactions between the insecticides flupyradifurone and sulfoxaflor and the fungicide azoxystrobin on honey bee health.   As the present study reveals, pesticide risk assessments do not inadequately capture the range of harm that can result when pesticides are combined, necessitating a shift toward safer, alternative, and regenerative organic farming systems that do not use these dangerous chemicals.For the initial experiment on individual bees, those exposed to flupyradifurone fared the worst, experiencing significantly reduced survival (50% reduction). The addition of azoxystrobin did not significantly add to this effect. However, with sulfoxaflor, it did. Bees subjected tsulfoxaflor and azoxystrobin in combination experienced significantly reduced survival when compared to a sole sulfoxaflor exposure.'     All experimental groups 'show significantly increased abundance of Serratia spp. This rod-shaped bacteria can serious harm honey bee fitness. “These bacteria are pathogenic and harmful to bees’ health,” said Dr. Al Naggar. “They can make it harder for the insects to fight off infection, leading to premature death.” 

Ingestion of Real-World Pesticide Residues in Grain Threatens Bird Offspring More than Parents    (Beyond Pesticides, September 8, 2022) A study published in Environmental Pollution finds parental exposure to real-world, sublethal concentrations of pesticide residues on grains is a major contributor to unfavorable offspring development among foraging birds. Parents’ ingestion of grains with conventional pesticide residues, whether from contaminated or pesticide-treated seeds, results in chronic exposure that adversely affects offspring health, even at low doses.    However, researchers find that ingestion of low pesticide residues in grain has consequences on reproduction and offspring quality without altering mortality. Chicks whose parents consume grains with pesticide residues are more petite in size, lack proper skeletal growth, and have lower red blood cell counts with increasing body mass index as a trade-off.

Direct pesticide exposure of insects in nature conservation areas in Germany  (Carsten A. Brühl et al; Scientific Reports,16 December 2021)    In total, residues of 47 current use pesticides were detected, and insect samples were on average contaminated with 16.7 pesticides. Residues of the herbicides metolachlor-S, prosulfocarb and terbuthylazine, and the fungicides azoxystrobin and fluopyram were recorded at all sites. The neonicotinoid thiacloprid was detected in 16 of 21 nature conservation areas, most likely due to final use before an EU-wide ban. The individual chemicals reflect sales volume of each.  A change in residue mixture composition was noticeable due to higher herbicide use in spring and increasing fungicide applications in summer. The number of substances of recorded residues is related to the proportion of agricultural production area in a radius of 2000 m. Therefore, a drastic pesticide reduction in large buffers around nature conservation areas is necessary to avoid contamination of their insect fauna.   see also Insects in Nature Preserves Contaminated with Over a Dozen Pesticides (Beyond Pesticides, January 13, 2022)   SNAP Comment: As mentioned in the article, the higher chemical detection reflects volume of sales so a similarly designed study in other locations would have to reflect pesticide use and persistence in the area. There are currently 32 PMRA registered pesticide products containing metolachlor in Canada, 0 present or historical containing prosulfocarb, 0 present or historical containing terbuthylazine,  44 (down from 49) containing azoxystrobin, 18 containing fluopyram and 4 containing the neonicotinoid thiacloprid.