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Pyrethrin

Pyrethrins are a group of six naturally occurring organic compounds extracted from the flowers of certain Chrysanthemum species, primarily Chrysanthemum cinerariifolium, that exhibit potent insecticidal properties by disrupting the nervous systems of insects, leading to paralysis and death.^[1] These compounds, collectively known as pyrethrins I and II (including pyrethrin I, cinerin I, and jasmolin I for the first group, and pyrethrin II, cinerin II, and jasmolin II for the second), have been used as insecticides since the early 19th century, with their insect-repelling effects first noted in Asia around 1800.^[2] The crude extract from the dried flowers is referred to as pyrethrum powder, which contains pyrethrins along with other plant impurities.^[1] Pyrethrins are widely employed in over 2,000 registered pesticide products worldwide, including household sprays, foggers, pet shampoos, and agricultural formulations for controlling pests such as mosquitoes, fleas, ticks, and flies.^[1] They are particularly valued in organic farming and public health applications due to their rapid breakdown in the environment—exhibiting half-lives of approximately 11.8 hours in water and 12.9 hours on soil under sunlight exposure—and relatively low toxicity to mammals, including humans.^[1] However, pyrethrins are highly toxic to aquatic organisms like fish and beneficial insects such as bees, necessitating careful application to minimize ecological impact.^[2] Often formulated with synergists like piperonyl butoxide to enhance efficacy, pyrethrins served as the chemical basis for the development of synthetic pyrethroids, which offer greater stability but are distinct from the natural forms.^[3]

Overview

Definition and Natural Sources

Pyrethrins are a class of natural organic compounds classified as esters, comprising six closely related insecticidal substances: pyrethrin I and II, cinerin I and II, and jasmolin I and II. These compounds are primarily extracted from the dried flower heads, particularly the seed casings, of the pyrethrum daisy, scientifically known as Tanacetum cinerariifolium, a perennial plant in the Asteraceae family.^[4]^[5]^[6] The natural occurrence of pyrethrins is limited to specific species in the genus Tanacetum (formerly classified under Chrysanthemum), with T. cinerariifolium serving as the principal source due to its high concentration of these esters in the glandular trichomes of its flowers. Commercial cultivation of this plant is concentrated in high-altitude regions, typically between 1,700 and 3,000 meters above sea level, where optimal cool and moist conditions enhance pyrethrin yields; major production areas include Kenya, the world's leading producer, and Tanzania.^[7]^[8]^[9]^[10] The term "pyrethrin" derives from the Greek word pyretos, meaning fever, reflecting the historical use of pyrethrum plants as febrifuges for treating fever-related ailments, with later associations in antimalarial efforts through mosquito control.^[11]^[12] In contrast to synthetic pyrethroids, which are laboratory-engineered analogs modified for enhanced stability and persistence, pyrethrins are exclusively naturally occurring and rapidly degrade in the environment.^[1]^[13]^[14]

Historical Development

The insecticidal properties of pyrethrum, the source of pyrethrins, were recognized in ancient Persia around 400 BCE, where dried flower powders from species like Tanacetum coccineum were used to repel insects and delouse children.^[15] Similar applications for insect repulsion are documented in ancient China and the Near East, where ground pyrethrum flowers served as a natural fumigant.^[16] These early uses remained localized until the 19th century, when pyrethrum flowers began to be imported into Europe from the Balkans and Caucasus regions, initially as "Persian insect powder" for commercial insecticide production starting in the 1840s.^[17] Commercial cultivation expanded in the late 19th century, with pyrethrum introduced to Japan around 1881 from England, leading to large-scale farming in regions like Wakayama by entrepreneurs such as Eiichiro Ueyama.^[18] In Africa, British colonists established pyrethrum cultivation in Kenya during the 1920s, transforming it into a major export crop by the 1930s and supporting the global supply for insecticides.^[19] A key innovation emerged in Japan in the 1890s, when Ueyama invented the spiral-shaped mosquito coil using pyrethrum powder mixed with binders, revolutionizing household insect control and driving demand for pyrethrum cultivation worldwide.^[20] Early 20th-century research advanced understanding of pyrethrins, with Japanese chemist Takeo Yamamoto identifying the cyclopropane ring structure in 1923, followed by the complete elucidation of pyrethrin I and II by U.S. chemists F.B. LaForge and W.F. Barthel in 1944.^[21] During World War II, pyrethrum demand surged for military use against disease vectors, but postwar introduction of synthetic alternatives like DDT led to a sharp decline in pyrethrum production by the 1950s.^[22] Interest resurged in the 1970s following bans on persistent organochlorine pesticides, including DDT in 1972, as pyrethrins offered a safer, biodegradable option amid growing environmental concerns.

Chemical and Biological Foundations

Molecular Structure and Properties

Pyrethrins are a class of six structurally related esters composed of three monoterpenoid acids—chrysanthemic, pyrethric, and jasmolinic—esterified to three alcohols: pyrethrolone, cinerolone, and jasmololone. The core molecular framework consists of a substituted cyclopropanecarboxylic acid linked via an ester bond to a monoterpenoid alcohol bearing a cyclopentenone ring. Pyrethrin I, the ester of (+)-trans-chrysanthemic acid and (S)-pyrethrolone, has the molecular formula \ce{C21H28O3} and a molecular weight of 328.45 g/mol. Pyrethrin II, formed from pyrethric acid and (S)-pyrethrolone, possesses the formula \ce{C22H28O5} and a molecular weight of 372.46 g/mol.^[23]^[24] These molecules exhibit complex stereochemistry due to multiple chiral centers and geometric isomerism in the side chains. The chrysanthemic acid moiety contains two chiral centers at positions 1 and 3 of the cyclopropane ring, resulting in cis and trans diastereomers; natural pyrethrins predominantly feature the (1R,3R)-trans configuration, which is essential for their biological activity. The pyrethrolone alcohol introduces an additional chiral center at C-3, yielding a total of three chiral centers and up to eight possible stereoisomers per pyrethrin. The pentadienyl side chain in pyrethrolone also allows for E/Z geometric isomerism, further contributing to structural diversity, though natural isolates are primarily the (2Z,4E) form.^[25] Physically, pyrethrins manifest as viscous, pale yellow to amber oils at room temperature, with low volatility (vapor pressure on the order of $10^{-7} mm Hg). They exhibit very low water solubility, typically less than 1 mg/L at 20°C and pH 7, but are highly soluble in organic solvents such as ethanol, acetone, and chloroform (up to 250 g/L). Their octanol-water partition coefficients (log K_{ow}) range from 4.3 for pyrethrin II to approximately 5.9 for pyrethrin I, reflecting strong lipophilicity and affinity for non-polar environments.^[23]^[24]^[26] Chemically, pyrethrins demonstrate stability in neutral and mildly acidic conditions, remaining intact for over 30 days at pH 5–7. However, as esters, they are susceptible to alkaline hydrolysis, rapidly degrading in basic media (pH >9) to yield the corresponding carboxylic acids and alcohols. Exposure to ultraviolet light induces photoisomerization, primarily converting trans forms to less active cis isomers, followed by oxidative degradation; the half-life under direct sunlight is typically 1–3 hours.^[27]^[28]^[29]

Biosynthesis Pathways

Pyrethrins are a class of natural insecticides biosynthesized in the flowers of Tanacetum cinerariifolium, primarily through terpenoid pathways that integrate isoprenoid precursors into complex ester structures. The biosynthesis begins with the formation of dimethylallyl pyrophosphate (DMAPP) and isopentenyl pyrophosphate (IPP), the universal building blocks of terpenoids, which are generated via the mevalonate (MVA) pathway in the cytosol and the 2C-methyl-D-erythritol 4-phosphate (MEP) pathway in plastids. These precursors condense to form geranyl pyrophosphate (GPP) and farnesyl pyrophosphate (FPP), which serve as substrates for the alcohol and acid moieties of pyrethrins, respectively. A critical early step involves the enzyme chrysanthemyl diphosphate synthase (CDS), which catalyzes the head-to-tail condensation of DMAPP and IPP to produce the irregular monoterpenoid chrysanthemyl diphosphate (CPP), the foundational alcohol component of all pyrethrins. This reaction is unique to pyrethrin-producing plants and is encoded by the gene TcCDS in T. cinerariifolium, where it exhibits specificity for the trans-isomer of IPP to ensure stereochemical fidelity in the final product. Subsequent hydrolysis of CPP, catalyzed by the bifunctional activity of chrysanthemyl diphosphate synthase (CDS) or a Nudix hydrolase such as TcNudix1, yields chrysanthemol, the primary alcohol precursor.^[30] The acid portions derive from oxidation of chrysanthemol to chrysanthemic acid via alcohol and aldehyde dehydrogenases. Pyrethric and jasmolinic acids involve additional modifications, including P450-mediated hydroxylations (e.g., CYP77B6v2 for C10 hydroxylation in pyrethric acid), oxidations, and incorporation of polyunsaturated chains from the jasmonic acid pathway, mediated by lipoxygenases and acyltransferases. Esterification links the acid and alcohol moieties via acyltransferases, such as those identified in the BAHD family (e.g., TcTPs), which transfer the acyl group from the acid-CoA thioester to the alcohol, producing the six pyrethrin esters (pyrethrins I and II, cinerins I and II, and jasmolins I and II). These enzymes show substrate promiscuity, allowing the formation of multiple analogs within glandular trichomes of the plant's capitula.^[31] Genetically, the pyrethrin pathway is regulated by a cluster of terpene synthase and cytochrome P450 genes in the T. cinerariifolium genome, with key loci like TcCDS and the terpene synthase gene TcTPS2 upregulated in flower heads compared to vegetative tissues. Environmental factors, including high altitude and intense light exposure, enhance expression of these genes by influencing jasmonic acid signaling, which activates pathway transcription factors and boosts pyrethrin accumulation up to 2-3% of dry flower weight. Transcriptomic studies have mapped over 20 pathway-related genes, revealing co-regulation that correlates with pyrethrin yield variations across cultivars. Post-2010 advances in metabolic engineering have elucidated pathway bottlenecks, with heterologous expression of TcCDS and associated P450s in Saccharomyces cerevisiae achieving detectable pyrethrin yields, though limited by precursor flux and enzyme stability; for instance, co-expression of IPP isomerase increased CPP production by 5-fold in yeast strains. These efforts, building on the draft genomic sequencing of T. cinerariifolium in 2019, aim to optimize synthetic biology platforms without fully reconstructing the pathway, focusing instead on rate-limiting steps like esterification efficiency. Recent studies (as of 2023) have identified transcription factors such as TcMYC2, TcbZIP60, and TcWRKY75 that positively regulate pyrethrin genes via jasmonic acid signaling, alongside chemical genetics tools targeting the esterase TcGLIP for pathway modulation.^[32]^[33]^[34]^[35]^[36]

Production and Commercial Aspects

Cultivation and Extraction Methods

Pyrethrum, the source of pyrethrins, is cultivated mainly in equatorial highland regions with cool climates and moderate rainfall, such as altitudes exceeding 1,800 meters above sea level, temperatures ranging from 15–25°C, and annual precipitation of 800–1,200 mm on well-drained soils with a pH of 6.0–7.0.^[37]^[38] Kenya was once a dominant producer, historically accounting for over 70% of global supply in the 1980s due to its ideal conditions, though its share has declined to around 2–10% in recent years amid competition from other producers and synthetics; as of 2024, Tanzania leads with approximately 13,941 hectares under cultivation and 8,360 metric tons of dried flowers produced.^[39]^[40]^[41]^[42] Kenya's cultivation area has expanded to 9,549 acres (about 3,863 hectares) in 2024, up 2% from 2023, with dry flower production reaching 1,634 metric tons in 2023 and government plans to distribute 1 million seedlings in 2025 to further revive output.^[43]^[44] Plants are propagated from seeds or cuttings and transplanted at densities of 4–8 plants per square meter to optimize growth and flower production.^[45]^[46] Harvesting occurs 4–6 months after planting, with flowers picked by hand when fully open to maximize pyrethrin content, which typically yields 0.8–1.5% by dry weight in mature flower heads.^[47]^[48] After harvest, pyrethrum flowers undergo drying in the sun or shade to reduce moisture content to about 10%, followed by grinding into a coarse powder to facilitate extraction.^[49] Traditional extraction employs non-polar solvents like hexane or petroleum ether in a percolation or immersion process, where the powdered flowers are soaked and the solvent is evaporated to yield a crude oleoresin containing 20–30% pyrethrins.^[50] Modern methods increasingly utilize supercritical carbon dioxide (CO₂) extraction, which operates at pressures of 200–400 bar and temperatures of 40–60°C, offering a solvent-free alternative that preserves pyrethrin integrity and achieves higher selectivity without residual solvents.^[51]^[52] The resulting extract is then purified through column chromatography or fractional distillation to produce a standardized concentrate of 45–55% total pyrethrins, suitable for commercial formulations.^[53] Cultivation faces several challenges, including labor-intensive manual harvesting due to the need for selective picking of individual flowers multiple times per season, which can involve 15–36 pickings annually per plant.^[54]^[55] Pests such as thrips, aphids, and diseases like ray blight (Didymella tanaceti) pose significant threats, requiring integrated management to prevent yield losses of up to 50% in affected fields.^[56] Global acreage under pyrethrum cultivation stands at approximately 25,000 hectares as of 2024, concentrated in East Africa, with ongoing efforts to expand through improved varieties and climate-resilient practices.^[41]^[57]^[55] Historically, extraction methods evolved from labor-intensive manual pressing and simple solvent immersion in the early 20th century to mechanized industrial processes post-1950s, incorporating continuous solvent extraction plants and automated drying systems that boosted efficiency and scaled production for global markets.^[20]^[58]

Modern Production Advances

Recent advances in pyrethrin production have focused on synthetic biology techniques to enable heterologous expression of biosynthetic genes in non-native hosts, aiming to overcome limitations of traditional extraction from Tanacetum cinerariifolium. Key enzymes such as chrysanthemyl diphosphate synthase (TcCDS), alcohol dehydrogenase (TcADH2), and aldehyde dehydrogenase (TcALDH) from pyrethrum have been cloned and co-expressed in tobacco (Nicotiana tabacum), resulting in the production of trans-chrysanthemic acid precursors at levels up to 1328 nmol/g fresh weight—a 48-fold increase over TcCDS alone. Similarly, the complete pyrethric acid pathway has been reconstituted in Nicotiana benthamiana through transient expression of TcCDS alongside four oxidoreductases (TcADH2, TcALDH1, TcCHH, and TcCCMT), yielding detectable amounts of pyrethric acid and demonstrating the feasibility of using fast-growing plants as biofactories for pyrethrin components. These lab-scale efforts, reported in studies from 2019 to 2022, highlight the potential for scalable, controlled production independent of field conditions.^[59]^[31]^[59] Sustainable agricultural practices have enhanced pyrethrin yield and environmental compatibility through organic farming initiatives in East Africa, where pyrethrum remains a key cash crop. In Kenya, companies like Kentegra support smallholder farmers with planting materials, training in integrated pest management (IPM), and long-term purchase contracts, reducing reliance on synthetic inputs and boosting farmer incomes by up to three times compared to other crops; this has revitalized production, which once accounted for over 80% of global supply. In Tanzania, the Pyrethrum Company of Tanzania (PCT) collaborates with thousands of organic family farms, investing in IPM-based organic pest control, improved seedstocks, and extension services to enable 10-month annual harvests while minimizing chemical use and soil degradation. These initiatives, active since the mid-2010s, promote biodiversity and climate resilience by integrating crop rotation and natural fertilizers.^[60]^[61]^[61] Alternative production sources include engineering pyrethrin pathways into other plants and exploring cell cultures to diversify supply. Tobacco has served as a model host for transient and stable expression of TcCDS and downstream genes, producing chrysanthemol and related esters that enhance pest resistance in the engineered plants. Efforts in tomato (Solanum lycopersicum) fruit-specific expression of TcCDS with Solanum habrochaites-derived ADH and ALDH have achieved trans-chrysanthemic acid levels of up to 183 μg/g fresh weight, suggesting tomatoes as a viable alternative platform. Plant cell suspension cultures of Chrysanthemum cinerariifolium have also shown promise for in vitro pyrethrin synthesis, with ongoing optimizations in media and elicitors to increase yields beyond traditional field levels, though commercial adoption remains limited. Market analyses indicate a growing shift toward such non-agricultural methods, driven by demand for organic pesticides, with the global pyrethrin market projected to reach USD 120.7 million by 2033 at a 6.3% CAGR, partly fueled by biotech innovations.^[7]^[62]^[63] Despite these progresses, challenges in scaling biotech approaches persist, including high engineering costs and suboptimal yields in heterologous systems, which currently lag behind natural pyrethrum extraction efficiency. However, these methods offer a reduced environmental footprint by decreasing land requirements, avoiding agrochemical runoff, and enabling year-round production in controlled settings like greenhouses to buffer against climate variability. Ongoing research emphasizes cost-effective pathway optimization to transition from lab to industrial scales, potentially transforming pyrethrin into a more accessible sustainable insecticide.^[64]^[65]^[66]

Applications and Uses

Insecticidal Applications

Pyrethrins exert their insecticidal effects primarily by binding to voltage-gated sodium channels in the nervous systems of insects, prolonging the open state of these channels and disrupting normal nerve impulse transmission. This binding leads to repetitive firing of neurons, resulting in hyperexcitation, uncoordinated movement, paralysis, and eventual death of the target insect.^[67] The compounds are classified into Type I and Type II based on their chemical structure and physiological impacts: Type I pyrethrins, lacking a cyano group, primarily induce rapid knockdown through tremors and hyperexcitability without prolonged convulsions, while Type II variants, containing a cyano group, cause more severe lethal effects including choreoathetosis and prostration due to enhanced channel modification.^[3] This selective neurotoxicity arises from differences in sodium channel isoforms between insects and mammals, making pyrethrins highly effective against arthropods at low doses.^[68] Common formulations of pyrethrins for insecticidal use include aerosols for space sprays, dusts for direct application, and emulsifiable concentrates that can be diluted into liquid sprays for broader coverage. These formulations facilitate quick dispersion and contact with pests in agricultural, household, and public health settings. To enhance efficacy and counteract insect detoxification mechanisms, pyrethrins are frequently combined with synergists such as piperonyl butoxide, which inhibits cytochrome P450 enzymes responsible for metabolizing the active compounds, thereby prolonging their activity without adding toxicity.^[69]^[70] Pyrethrins demonstrate broad-spectrum efficacy against a variety of pests, including mosquitoes, flies, aphids, and beetles, making them suitable for both agricultural crop protection and vector control. Historically, pyrethrum-based insecticides, from which pyrethrins are derived, played a key role in military applications during the 1940s, particularly in malaria prevention efforts where they were used to target Anopheles mosquitoes in theaters like the Pacific and Mediterranean, reducing disease incidence among troops through aerosol and residual treatments.^[1]^[71] A primary advantage of pyrethrins lies in their rapid knockdown effect, immobilizing insects within minutes of exposure, which is ideal for immediate pest control in sensitive environments. Additionally, their low environmental persistence—degrading rapidly in sunlight and air within hours to days—minimizes long-term residue accumulation compared to more stable synthetic alternatives.^[1]^[72]

Non-Insecticidal Uses

Pyrethrins are employed in medical applications primarily as pediculicides for treating human lice infestations, including head, body, and pubic lice. They are formulated in topical shampoos and lotions, typically at concentrations equivalent to 0.33% pyrethrins combined with piperonyl butoxide as a synergist, which enhances efficacy by inhibiting insect detoxification enzymes. These products work by disrupting the nervous system of lice, leading to paralysis and death, though a second application is often required after 9-10 days to target newly hatched nymphs.^[73]^[74]^[75] In veterinary medicine, pyrethrins serve as key ingredients in flea and tick control products for dogs, available in shampoos, spot-on treatments, collars, and dusts. These formulations provide rapid knockdown of ectoparasites, with veterinarians recommending them for their relatively low mammalian toxicity compared to alternatives like organophosphates. However, pyrethrins are highly toxic to cats due to their deficient glucuronidation pathway, which impairs detoxification, necessitating strict separation of dog and cat products to avoid accidental exposure.^[76]^[77] Beyond parasiticide roles, pyrethrins find limited use as natural insect repellents in cosmetic and personal care products, such as lotions and sprays, where they deter mosquitoes and other biting insects through olfactory disruption of insect sensory receptors. Their incorporation remains niche due to rapid environmental degradation and the need for frequent reapplication.^[78] The broader pharmaceutical adoption of pyrethrins is constrained by their low water solubility (typically <1 mg/L), which complicates formulation stability and bioavailability in systemic or diverse topical delivery systems. Consequently, non-insecticidal applications represent a small portion of total pyrethrin use, primarily in veterinary ectoparasite control and human pediculicides. Pyrethrins are also registered for non-insecticidal purposes, including as bactericides, disinfectants, and antimicrobials in various formulations.^[1]^[76]

Safety Profile

Toxicity in Humans

Pyrethrins, natural insecticides derived from chrysanthemum flowers, primarily affect humans through acute exposure via dermal contact, inhalation, or ingestion, with dermal and inhalation routes accounting for the majority of incidents based on poison control data. Acute effects often include skin irritation, such as redness and itching, and respiratory symptoms like coughing or shortness of breath following inhalation of aerosolized formulations. Dermal exposure can also cause paresthesia, a tingling or burning sensation, due to the compounds' action on sodium channels in nerve cells, which is typically transient and resolves without treatment. In rare cases, sensitized individuals may experience anaphylaxis, manifesting as severe allergic reactions including bronchospasm and hypotension, particularly from inhalation or contact with pyrethrin-containing products like shampoos.^[79]^[80]^[81] Notable case studies highlight the risks of acute exposure; for instance, in the 1980s and early 1990s, several fatalities were reported from inhalation exposure to pyrethrin-based dog shampoos during use, leading to bronchospasm, pulmonary edema, and respiratory failure in individuals with underlying asthma or allergies. These incidents underscore the potential for severe outcomes when pyrethrins are inhaled, though such events are uncommon with proper application. Occupational exposure in agricultural or pest control settings can exacerbate acute symptoms, but most cases are mild and self-limiting.^[79]^[82] Chronic exposure to pyrethrins, typically through repeated occupational handling or household use, may lead to neurotoxicity at high doses, including headaches, dizziness, and fatigue, though evidence is limited and primarily derived from case reports rather than large-scale studies. There are no strong links to cancer, with the U.S. EPA classifying pyrethrins as Group D ("not classifiable as to human carcinogenicity") based on inadequate evidence from animal studies and lack of human data. The World Health Organization has established an acceptable daily intake (ADI) of 0–0.04 mg/kg body weight per day, reflecting low risk from typical dietary or environmental levels. Recent biomonitoring studies from 2020–2025 indicate low urinary metabolite concentrations in the general population, suggesting minimal widespread chronic exposure, but elevated levels in children from household insecticides raise concerns for potential neurodevelopmental effects, such as subtle impacts on cognition and motor skills; a 2025 study confirmed low overall risk but highlighted higher exposures in insecticide-using households.^[79]^[29]^[83]^[84]

Toxicity in Animals

Pyrethrins exhibit low acute toxicity in most mammals, with oral LD50 values typically exceeding 1000 mg/kg in rats, indicating a wide margin of safety for species like rodents and dogs. For instance, undiluted pyrethrum extract has an oral LD50 of 2370 mg/kg in male rats and 1030 mg/kg in females. Dogs generally tolerate pyrethrins well, allowing safe use in veterinary flea control products at appropriate concentrations. However, cats demonstrate markedly higher sensitivity due to inefficient hepatic glucuronidation, which impairs the detoxification of pyrethrins and related pyrethroids; toxicity can occur even from low-concentration products (e.g., >0.1% in some formulations), leading to symptoms such as tremors, muscle fasciculations, hypersalivation, and seizures. Case reports document feline fatalities from grooming dogs treated with pyrethrin-based spot-on flea products, underscoring the need for species-specific formulations and avoiding dog products in multi-pet households.^[79]^[29]^[85]^[86]^[87] In birds and livestock, pyrethrins pose a moderate risk, with oral LD50 values often above 1000 mg/kg. Livestock species, including cattle and sheep, experience low systemic toxicity from topical applications used for ectoparasite control, though excessive dosing can cause transient skin irritation or neuroexcitatory signs like ataxia. Interspecies biotransformation differences contribute to varying sensitivities; mammals primarily metabolize pyrethrins via ester hydrolysis and oxidation in the liver, with rapid excretion in urine, whereas birds and some livestock may have slower clearance rates, prolonging exposure effects. Pyrethrins are highly toxic to aquatic organisms (detailed in Ecological Impacts).^[88]^[29]^[89] Post-2020 veterinary guidelines emphasize safe dosing to mitigate risks, recommending pyrethrin concentrations below 0.2% for cats and avoiding shared use of dog products in multi-pet households, with supportive treatments like lipid emulsion therapy for intoxications. No major outbreaks of pyrethrin toxicity in animals have been reported through 2025, reflecting improved labeling and formulation standards. These measures parallel human safety protocols by prioritizing rapid decontamination and monitoring for neurotoxicity.^[80]^[90]

Environmental and Regulatory Considerations

Ecological Impacts

Pyrethrins exhibit high toxicity to aquatic organisms, particularly fish and invertebrates, with 96-hour LC50 values for fish typically ranging from 0.01 to 1 µg/L, indicating extreme sensitivity even at low concentrations.^[91] This acute lethality arises from disruptions to nerve function in these species, leading to rapid immobilization and death upon exposure. Invertebrates, such as crustaceans and aquatic insects, face similarly severe risks, with LC50 values often below 0.1 µg/L, exacerbating population declines in contaminated water bodies.^[92] Although bioaccumulation in aquatic organisms is low due to rapid hydrolysis in water—often occurring within hours under sunlight or neutral pH conditions—agricultural runoff remains a primary concern, transporting residues into streams and wetlands where they can persist in sediments.^[29]^[93] In terrestrial ecosystems, pyrethrins harm soil microbes by inhibiting microbial respiration and enzyme activity, which can disrupt nutrient cycling and organic matter decomposition essential for soil health.^[13] Earthworms, key indicators of soil quality, experience sublethal effects including reduced burrowing and reproduction at environmentally relevant doses, potentially altering soil structure and aeration over time.^[94] Persistence in soil varies from 1 to 30 days, influenced by factors like sunlight exposure and microbial activity; half-lives are shorter (0.6–1.9 days) on sunlit surfaces but extend beyond 7 days in shaded or anaerobic conditions, allowing intermittent exposure to soil biota.^[1]^[29] Pyrethrins are lethal to pollinators, with an acute contact LD50 for honey bees of approximately 0.04 µg/bee, classifying them as highly toxic and capable of causing direct mortality during foraging.^[95] Sublethal exposures impair bee navigation, foraging efficiency, and reproductive success, leading to reduced colony fitness and increased vulnerability to stressors.^[96] Studies from the 2020s have linked pyrethroid residues to contributions in colony collapse disorder, where chronic low-level contamination correlates with higher rates of hive abandonment and overwintering losses.^[97] Overall, pyrethrins are biodegradable, primarily through photodegradation and microbial action, minimizing long-term accumulation in ecosystems.^[1] However, spray drift during application amplifies risks by depositing residues onto non-target habitats, including water bodies and pollinator foraging areas, potentially increasing exposure beyond intended sites.^[98] Mitigation strategies, such as establishing vegetated buffer zones around fields, can reduce drift and runoff impacts by 50–70%, effectively lowering pesticide transport to adjacent ecosystems.^[99]

Regulatory Status and Future Research

Pyrethrins are classified by the U.S. Environmental Protection Agency (EPA) as active ingredients eligible for use in minimum risk pesticides under Section 25(b) of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), allowing certain formulations to be exempt from full registration requirements when combined with specified inert ingredients.^[100] However, pyrethrins undergo periodic registration review, with the EPA releasing a draft ecological risk assessment in March 2025 to evaluate potential environmental impacts from their use alongside synthetic pyrethroids; as of November 2025, the review process is ongoing with no final decision issued.^[101] In the European Union, pyrethrins remain approved as an active substance under Regulation (EC) No 1107/2009, with maximum residue levels (MRLs) set between 0.05 mg/kg and 0.5 mg/kg for various crops such as fruits and vegetables, above the default 0.01 mg/kg limit for unlisted commodities.^[102] Restrictions apply in organic farming, where pyrethrins are permitted in some regions like the EU and U.S. due to their natural origin.^[103] Pyrethrins are used for vector control applications, particularly in space sprays for malaria prevention, as a natural alternative to synthetic pyrethroids amid rising resistance concerns. Recent reviews from 2023 to 2025 on endocrine disruption potential have yielded inconclusive results, with some studies indicating possible estrogenic effects in vertebrates but lacking definitive evidence of disruption in humans or wildlife at typical exposure levels.^[104]^[105] Future research priorities include addressing gaps in long-term environmental monitoring of pyrethrin residues in soil and water, as current data often overlook cumulative effects over extended periods.^[98] Investigations into climate change influences on pyrethrin degradation rates are emerging, with studies showing elevated temperatures and altered precipitation may slow breakdown and heighten toxicity to non-target species.^[106] Efforts are also focusing on developing alternatives to synergists like piperonyl butoxide, which amplify efficacy but raise resistance risks, alongside biotechnological approaches to engineer safer pyrethrin analogs with enhanced specificity and reduced environmental persistence.^[107]^[65] Industry trends reflect a shift toward integrated pest management (IPM) strategies that incorporate pyrethrins to minimize synthetic pesticide reliance, supported by their rapid degradation profile.^[108] Despite competition from cheaper synthetic pyrethroids, the global pyrethrin market is projected to reach approximately $414 million by 2030, driven by demand for natural insecticides in organic agriculture and public health applications.^[109]

References

[1]
Pyrethrins General Fact Sheet - National Pesticide Information Center
Pyrethrins are pesticides found naturally in some chrysanthemum flowers. They are a mixture of six chemicals that are toxic to insects.Missing: properties | Show results with:properties
[2]
Public Health Statement for Pyrethrins and Pyrethroids - CDC
Pyrethrum is a naturally occurring mixture of chemicals found in certain chrysanthemum flowers. Pyrethrum was first recognized as having insecticidal properties ...
[3]
Toxicological Profile for Pyrethrins and Pyrethroids - NCBI - NIH
Pyrethrum has long been recognized as possessing insecticidal properties; over the years, first the chemical extracts of pyrethrum, and then more recently, the ...Missing: sources | Show results with:sources
[4]
Draft genome of Tanacetum cinerariifolium, the natural source ... - NIH
Dec 3, 2019 · Pyrethrum (Tanacetum cinerariifolium), which is a perennial Asteraceae plant with white daisy-like flowers, is the original source of mosquito ...
[5]
Action of six pyrethrins purified from the botanical insecticide ...
May 3, 2018 · Pyrethrin I, pyrethrin II, cinerin I, cinerin II, jasmolin I and jasmolin II are six closely related insecticidal active esters, ...
[6]
Understanding pyrethrin biosynthesis: toward and beyond natural ...
Aug 13, 2024 · Pyrethrins are oily compounds comprised of six components (pyrethrin I/II, cinerin I/II, and jasmolin I/II Figure 1), which complicated early ...
[7]
Review How Plants Synthesize Pyrethrins: Safe and Biodegradable ...
Pyrethrin I is the most abundant of the six pyrethrins in T. cinerariifolium while pyrethrin II is the second-most abundant (relative abundances of jasmolins ...
[8]
[PDF] Strategies for the development of a competitive pyrethrum-based ...
Pyrethrum is Kenya's fourth largest cash crop and the country is the world's leading producer. The crop is cultivated, at high altitude, by small scale farmers ...
[9]
Pyrethrum Matters - Tanzania Pyrethrum Board
The commercial cultivation takes place at an altitude of 1700 to 3000 meters above sea level. This is done because pyrethrin concentration has been shown to ...Missing: high- | Show results with:high-
[10]
[PDF] rafi communique - ETC Group
It is mainland Tanzania's eighth ranking agricultural product, produced by many thousands of small farmers in high altitude regions of Iringa and Mbeya where ...<|separator|>
[11]
PYRETHRUM Definition & Meaning - Dictionary.com
Word History and Origins. Origin of pyrethrum. C16: via Latin from Greek purethron feverfew, probably from puretos fever; see pyretic. Discover More. Compare ...Missing: etymology | Show results with:etymology
[12]
Historical review of malarial control in southern African with ...
Aug 10, 2004 · In southern Africa the first experimental adult mosquito control with pyrethrum was carried out in 1931 in KwaZulu-Natal, South Africa and this ...
[13]
Pyrethrins and Pyrethroids: A Comprehensive Review of Natural ...
Synthetic pyrethroids have replaced natural pyrethrums due to their improved effectiveness and stability against insects, making them valuable tools for pest ...
[14]
Pyrethrins vs. Pyrethroids: What's the difference? - MGK
Pyrethrins are broad spectrum and kill a wide variety of insects, while pyrethroids tend to have longer residual effects and increased stability in storage.
[15]
Pyrethrin - an overview | ScienceDirect Topics
The use of pyrethrum in insecticide preparations dates back to Persia, about 400 BC. Pyrethroids are synthetic analogs of pyrethrins. Because of stability ...Missing: BCE | Show results with:BCE
[16]
[PDF] Pyrethroid insecticides - Arkivoc
Feb 11, 2021 · in various parts of the world (Dalmatia, Persia, China) and the ground plants have been used as “Persian powder”, “Persian dust” or “Insect ...
[17]
Pyrethrum: History of a Bio-Insecticide – Part 1 - ChemistryViews
Oct 2, 2018 · Around 1900, scientists with the state wine-growing research station in the Swiss canton of Waadt tested nearly 80 different substances for ...Missing: antimalarial | Show results with:antimalarial
[18]
Introduction of pyrethrum flowers (130 years in Japan) - ResearchGate
Aug 5, 2025 · ... Pyrethrum (C. cinerariifolium) was introduced to Japan from England in either 1881 (Gnadinger, 1945) or 1885 (Ueyama, 2017) .<|control11|><|separator|>
[19]
The Pyrethrum Industry's Legacy in Kenya's Agrochemical Landscape
Jan 2, 2025 · Introduced to Kenya in 1928 under British rule for the production of insecticides, pyrethrum quickly became a significant export crop by the ...Missing: Japan 1880s 1920s
[20]
The history of extensive structural modifications of pyrethroids - PMC
Nov 20, 2019 · As Japan had a big share in the pyrethrum market in the early 1900s, many of the early pyrethrum studies were conducted in Japan. The first ...
[21]
Discovery and development of pyrethroid insecticides - PMC - NIH
In 1924, Staudinger and Ruzicka, both Nobel prize winners, disclosed their extensive investigation during 1910–1916 on the active ingredients in the pyrethrum ...Missing: antimalarial | Show results with:antimalarial
[22]
Pyrethrum and the Second World War:Recontextualising DDT in the ...
Jan 4, 2023 · This paper tells a very different story of wartime insecticides. We recontextualise DDT in the wider wartime technological landscape and in so ...
[23]
Pyrethrin I | C21H28O3 | CID 5281045 - PubChem - NIH
Pyrethrin I | C21H28O3 | CID 5281045 - structure, chemical names, physical ... Molecular Formula. C21H28O3. Synonyms. PYRETHRIN I; 121-21-1; Piretrina 1 ...
[24]
Pyrethrin II | C22H28O5 | CID 5281555 - PubChem - NIH
Pyrethrin II is a natural organic compound also called pyrethrolone ester of chrysanthemummonocarboxylic acid. It consists of structurally related esters ...
[25]
[PDF] 4. CHEMICAL AND PHYSICAL INFORMATION
Pyrethroids such as cyfluthrin, cypermethrin, and cyhalothrin possess three chiral centers, and thus consist of eight possible isomers. The production of ...
[26]
Pyrethrins (pyrethrin I) - AERU - University of Hertfordshire
The cyclopropane ring in chrysanthemic acid introduces two chiral centres, allowing for multiple stereoisomers. These include cis- and trans-isomers, based ...
[27]
[PDF] pyrethrins - Food and Agriculture Organization of the United Nations
Hydrolysis (PY 1): stable at pH 5 and pH 7 for 30 days ... In both goats and hens, pyrethrin 1 can undergo hydrolysis to form trans-chrysanthemic acid, which is ...
[28]
Degradation of Pyrethrin Residues on Stored Durum Wheat after ...
Because of their photolability, pyrethrins when exposed to sunlight showed half-life times of a few minutes ( 5), while in a field experiment on peaches ...
[29]
[PDF] ATSDR Pyrethrins and Pyrethroids Tox Profile
PHYSICAL AND CHEMICAL PROPERTIES. Information regarding the physical and chemical properties of the pyrethrins and selected pyrethroids are located in Tables ...
[30]
Pyrethrum Farming in Kenya - Safi Sarvi Organic Fertilizer
Jul 31, 2024 · Elgeyo-Marakwet County: The high-altitude areas in Elgeyo-Marakwet, especially around the Kerio Valley, offer ideal conditions for pyrethrum.
[31]
Pyrethrum Growing Suitability Factors in Kenya - LinkedIn
Jun 14, 2024 · Altitude. Pyrethrum grows best at high altitudes around 1980 meters above sea level. However, some varieties are suitable for lower altitudes ...
[32]
The $50 million daisy: Is Kenya's pyrethrum revival real? - IOL
Sep 16, 2025 · By the 1980s, Kenya dominated global pyrethrum production, supplying over 70% of the world's natural insecticide market. Some 300 000 farmers ...
[33]
Industrial Africa Business Idea With A Flower: Pyrethrum
Dec 5, 2014 · ... Kenya. In the past, Kenya delivered 57 percent of the global demand of this natural insecticide. Today it's only about 2 percent. The sector ...
[34]
[PDF] Effects of plant population on pyrethrins yield of pyrethrum ...
Past density studies conducted on pyrethrum have investigated plant populations in the range two to nine plants/m2. Yield increases were reported for plantings ...
[35]
PYRETHRUM FARMING - africhem botanicals
Pyrethrum needs 750mm rainfall, 2000m altitude, well-tilled land, 2ft inter-row, 1ft intra-row spacing, and is transplanted after 3-4 years.Missing: optimal | Show results with:optimal
[36]
Pyrethrum farming comprehensive guide for organic insecticides
May 30, 2025 · Temperature: Prefers cool climates (13–25°C). Rainfall: Requires 900–1,200 mm of rainfall annually, well-distributed.Pyrethrum farming for organic insecticides production guideA Comprehensive Guide Pyrethrum farming is the ... - FacebookMore results from www.facebook.com
[37]
Comparative analysis of pyrethrin content improvement by mass ...
Pyrethrins accumulate to 1–2% of dry mass in the mature flower heads, which are then harvested, dried, and powdered [1,55]. The powdered material may then be ...
[38]
How is Organic Pyrethrum Harvested? | The Power of the Flower
The pyrethrum daisies are harvested once they have bloomed. They are cut, then left to dry in the sun before the dried flower heads are collected and ...
[39]
Two Step Extraction Of Pyrethrins From Pyrethrum | UKEssays.com
Apr 28, 2017 · The first-step involves using n-hexane as solvent to extract the pyrethrins from the solid sample (grounded and unsieved with particles size of ...
[40]
Supercritical Extraction of a Natural Pyrethrin-Rich Extract ... - MDPI
Jun 8, 2022 · Supercritical carbon dioxide has been proven to be an effective technique for the extraction of pyrethrins from chrysanthemum flowers. When ...
[41]
Pyrethrin exraction from pyrethrum flowers using carbon dioxide
Supercritical extraction from solid substrate using carbon dioxide as solvent, with or without the addition of cosolvent, has proved to be technically feasible.
[42]
Pyrethrins | C43H56O8 | CID 60202781 - PubChem - NIH
Pyrethrins | C43H56O8 | CID 60202781 - structure, chemical names, physical and chemical ... Molecular Formula. C43H56O8. Synonyms. Pyrethrins; Pyrethroid ...
[43]
Pyrethrins in Tanacetum cinerariifolium biosynthesis, regulation, and ...
Jun 3, 2024 · Around 400 BC, during Persian king Xerxes' reign, pyrethrum was used for its dried flower powder to delouse children.Missing: BCE | Show results with:BCE
[44]
(PDF) Diseases of Pyrethrum in Tasmania - ResearchGate
Aug 10, 2025 · Diseases of Pyrethrum in Tasmania: Challenges and Prospects for Management. September 2008; Plant Disease 92(9). DOI:10.1094/PDIS-92-9-1260.<|control11|><|separator|>
[45]
World major producers of dried Pyrethrum flowers in year 2016 ...
In 2018, Tanzanian Pyrethrum was grown to a total production area equal to 13,941 hectares and 7,036 tonnes of dried Pyrethrum flowers were produced (FAO, 2020) ...
[46]
South Korea, UK fastest-growing export markets for Kenya's pyrethrum
Sep 11, 2025 · Kenya's pyrethrum extract exports to South Korea posted a substantial increase, amounting to 8,550 Kg or 27.9 percent. The United Kingdom also ...Missing: supply | Show results with:supply
[47]
[PDF] History of Pyrethrum - Sci-Hub
Of course, World War II completely shut off supply from Japan and greatly encouraged the production of pyrethrum in Africa, especially. Kenya, Tanganyika, and ...Missing: 1880s 1920s colonists
[48]
Research Progress on the Synthetic Biology of Botanical Biopesticides
May 12, 2022 · Xu et al. explored the pathway for pyrethrin production in tobacco by co-expressing the key enzymes TcCDS, TcADH2, TcALDH1, TcCHH, and TcCCMT.
[49]
Pyrethric acid of natural pyrethrin insecticide: complete pathway ...
Mar 28, 2019 · In combination with the previously identified gene TcCDS, these four genes were sufficient to engineer pyrethric acid production in the ...
[50]
Revitalizing Kenya's organic pesticide industry and improving ... - DFC
Kenya once produced over 80 percent of the world's pyrethrum, a white flower that looks like a daisy and produces an active ingredient used to create ...Missing: global | Show results with:global
[51]
Pyrethrum Company of Tanzania: Building Sustainability and ... - MGK
Over time, a sustainable industry emerged that consists of thousands of small organic family farms that harvest pyrethrum flowers 10 months out of the year.
[52]
The production of pyrethrins by plant cell and tissue cultures of ...
The world production of natural pyrethrins still falls short of global market demand stimulating the research in in vitro production as an alternative to ...
[53]
Pyrethrin Market Size, Share, Trends and Industry Analysis 2033
The global pyrethrin market size was valued USD 67.7 Million in 2024 to reach USD 120.7 Million by 2033 at a CAGR of 6.3% during 2025-2033.Missing: acreage hectares
[54]
Green Chemistry: The Environmental Impact and Sustainability of ...
Jul 18, 2024 · One of the main challenges in large - scale production of pyrethrins is the variability in yield and quality of the pyrethrum plants. The ...Missing: footprint | Show results with:footprint
[55]
Biomimetic and Synthetic Advances in Natural Pesticides: Balancing ...
Jun 19, 2025 · Table 2 outlines the key challenges in scaling synthetic natural pesticides, including high production costs, operational complexity ...<|control11|><|separator|>
[56]
Protecting crops and the environment with natural pyrethrins
Dec 24, 2024 · This article explores their unique properties, differences from synthetic pyrethroids, and their critical role in reducing environmental impact.<|separator|>
[57]
Voltage-gated sodium channels as targets for pyrethroid insecticides
Jan 9, 2017 · The mode of action of pyrethroids is known to be via interactions with the voltage-gated sodium channel.
[58]
Molecular biology of insect sodium channels and pyrethroid resistance
Sodium channels have two receptor sites for pyrethroids. Abstract. Voltage-gated sodium channels are essential for the initiation and propagation of the action ...
[59]
[PDF] Pyrethrins and Pyrethroid Insecticides - Montana State University
The widespread use of pyrethroids began in the 1970s after the development of photostable pyre like permethrin and fen valerate. Pyrethroid use has increased ...
[60]
Piperonyl butoxide (PBO) combined with pyrethroids in insecticide ...
Nov 29, 2018 · Piperonyl butoxide (PBO) is a synergist that inhibits specific metabolic enzymes within mosquitoes and has been incorporated into pyrethroid ...
[61]
The role of the United States military in the development of vector ...
Jul 10, 2009 · Because insects avoid pyrethrum, pyrethrum also has repellent effects. Major Gorgas used pyrethrum in Cuba to control yellow fever and malaria ...
[62]
Pyrethrin - an overview | ScienceDirect Topics
Pyrethrins are effective insecticides, having very low dose rates and rapid knockdown of insects but being harmless to mammals under all normal conditions.Missing: advantages | Show results with:advantages
[63]
Clinical Care of Head Lice - CDC
Jan 31, 2025 · Pyrethrins can only kill live lice, not unhatched eggs (nits). Treat a second time 9 – 10 days after the first treatment to kill any newly hatched lice before ...Missing: inflammatory | Show results with:inflammatory
[64]
Pyrethrin and Piperonyl Butoxide Topical - MedlinePlus
Nov 15, 2015 · Pyrethrin and piperonyl butoxide shampoo is used to treat lice (small insects that attach themselves to the skin on the head, body, or pubic area ['crabs'])Missing: inflammatory | Show results with:inflammatory
[65]
Pyrethrum extract and piperonyl butoxide (Topical) - Drugs.com
Oct 14, 2024 · Uses for pyrethrum extract and piperonyl butoxide. Medicine containing pyrethrins is used to treat head, body, and pubic lice infections.
[66]
[PDF] Pyrethrins (PC Code 06900 - Regulations.gov
Jun 29, 2021 · This memorandum reviews the non-agricultural uses and related benefits of pyrethrins and two non-insecticidal synergists often used to increase ...<|control11|><|separator|>
[67]
The Flea-Infested Pet: Overview of Current Products
These synergists are typically well tolerated in dogs and cats when used at label doses. However, pyrethrins and many synergists may be highly toxic to other ...
[68]
A Mixture of Natural Pyrethrins Has Potential for Malaria Vector Control
May 1, 2009 · In conclusion, this study showed that pyrethrum may be promising for malaria vector control, especially for the impregnation of bednets and ...Missing: antimalarial | Show results with:antimalarial
[69]
A dual-target molecular mechanism of pyrethrum repellency against ...
May 5, 2021 · Pyrethrins and pyrethroids exert potent insecticidal activities by hyper-activating insect voltage-gated sodium channels, thereby causing rapid paralysis.
[70]
Phytochemistry, Biological and Pharmacological Activities of the ...
These active substances possess antimicrobial and anti-inflammatory activities. The plant has an antidiabetic, insecticidal and immunostimulatory effect, as ...
[71]
HEALTH EFFECTS - Toxicological Profile for Pyrethrins and ... - NCBI
Toxicity among the various pyrethroids varies greatly, as is evidenced by the wide range in LD50 values (concentrations or doses that result in 50% mortality in ...DISCUSSION OF HEALTH... · TOXICOKINETICS · BIOMARKERS OF...
[72]
Pyrethrin and Pyrethroid Toxicity - StatPearls - NCBI Bookshelf
Aug 11, 2024 · Pyrethrin and pyrethroid compounds are ester insecticides derived from Chrysanthemum cinerariaefolium, with robust safety profiles in humans ...Missing: etymology Greek antimalarial
[73]
The Facts on Pyrethroid Poisonings
If a person is exposed to a large amount of pyrethroid, they can develop nausea, vomiting, diarrhea, headache, dizziness, tingling, numbness, a “pins and ...
[74]
Fatality associated with inhalation of a pyrethrin shampoo - PubMed
A fatality associated with the inhalational exposure to a pyrethrin insecticide is described. Death was attributed to sudden irreversible bronchospasm.Missing: aspiration 1980s
[75]
[PDF] D PYRETHRINS (addendum) First draft prepared by Rudolf Pfeil ...
The 1999 JMPR established an acceptable daily intake (ADI) of 0–0.04mg/kgbw on the basis of the no-observed- adverse-effect level (NOAEL) for liver effects in a ...
[76]
Biomonitoring-Based Risk Assessment of Pyrethroid Exposure in the ...
Mar 16, 2025 · This study evaluated the exposure risk by age using available biomonitoring data. We analyzed pyrethroid metabolite concentrations in urine.
[77]
Pyrethrin/Pyrethroid Poisoning in Dogs - VCA Animal Hospitals
The use of pyrethrins/pyrethroids is generally safe in dogs; however, cats and fish are very sensitive to these products.Missing: livestock | Show results with:livestock
[78]
Pyrethrin Toxicity in Cats - MSPCA-Angell
Pyrethrin toxicity in cats, often from flea treatments, causes neuroexcitation, twitching, tremors, and seizures. Cats are more susceptible due to their liver.
[79]
Pyrethrin toxicosis in a cat | VetGirl Veterinary CE Videos
Sep 23, 2024 · Due to a cat's altered liver glururonidation metabolism, cats are significantly more sensitive to pyrethrins than dogs. While a precise toxic ...
[80]
[PDF] Synthetic Pyrethroids - Beyond Pesticides
Overall, type I pyrethroids are less toxic to mammals than type II pyrethroids (Rehman et al., 2014). Synthetic pyrethroids are not easily absorbed through ...
[81]
PYRETHRINS AND PYRETHROIDS - EXTOXNET PIP
Pyrethrin is extremely toxic to aquatic life, such as bluegill and lake trout while it is slightly toxic to bird species, such as mallards. Toxicity increases ...
[82]
Pyrethrins and pyrethroids: Educating clients on certain topical flea ...
May 28, 2025 · Though different, they impact cats the same. Pyrethrins and pyrethroids are often used in preventatives that are labeled for dogs, since they ...
[83]
Toxicity of pyrethroid insecticides to fish - Oxford Academic
Exposures of fish to sublethal concentrations of pyrethroids have resulted in decreased growth and impaired swimming performance. The effects on bioenergetics ...
[84]
Toxicological effects of pyrethroids on non-target aquatic insects
Aquatic insects are highly sensitive to toxicological effect of pyrethroids. Susceptibility may be related to biochemical and physiological constraints.
[85]
Aquatic Toxicity Due to Residential Use of Pyrethroid Insecticides
Nearly all creek sediments collected caused toxicity in laboratory exposures to an aquatic species, the amphipod Hyalellaazteca, and about half the samples ...Missing: animals | Show results with:animals
[86]
Long-term toxic effects of deltamethrin and fenvalerante in soil
May 30, 2015 · The results of several studies have indicated that pyrethroids are biotoxic to fish, bees and earthworms in the environment (Brander et al., ...
[87]
ENY-162/IN1027: Minimizing Honey Bee Exposure to Pesticides
If the LD50 = 11 µg/bee, then the pesticide is considered practically non-toxic to bees at an acute level. Information on pesticide labeling and protection of ...<|separator|>
[88]
Pyrethroids and Nectar Toxins Have Subtle Effects on the Motor ...
Aug 17, 2015 · Bees exposed to these compounds spent more time upside down and fanning their wings. They also had longer bouts of standing still. Bees exposed ...
[89]
Pesticides and Their Involvement in Colony Collapse Disorder
Aug 20, 2019 · If pesticides are applied anytime during bloom, bees will be killed; even the shortest duration pesticides like pyrethroids are not disappearing overnight.<|control11|><|separator|>
[90]
[PDF] US EPA - Pyrethroids and Pyrethrins Revised Ecological Risk ...
The Agency issued a single risk mitigation proposal to address ecological risks for 23 pesticides, which encompass the pyrethrins, synthetic ...<|control11|><|separator|>
[91]
A review of the effectiveness of vegetated buffers to mitigate ...
Aug 7, 2025 · The reported effectiveness of vegetated buffers in reducing the movement of pesticides and nutrients ranged from 10 to 100% and 12 to 100%, ...Missing: pyrethrins | Show results with:pyrethrins<|separator|>
[92]
Minimum Risk Pesticides Exempted from FIFRA Registration | US EPA
Oct 6, 2025 · EPA has exempted them from the requirement that they be registered under the Federal Insecticide, Fungicide, and Rodenticide Act.Conditions for Minimum Risk... · Pesticide · State Regulation of Minimum...Missing: pyrethrins | Show results with:pyrethrins
[93]
Registration Review of Pyrethrins and Pyrethroids | US EPA
Mar 12, 2025 · EPA released a draft ecological risk assessment for eight pyrethroids plus the pyrethrins and a risk management rationale for the remaining pyrethroids.
[94]
EU Pesticides Database - Active substances - European Commission
Active substance: Pyrethrins · Status under Reg. (EC) No 1107/2009Approved · Authorisation at national level · EU - Maximum Residue Levels · Classification Reg.
[95]
[PDF] Frequently asked questions ON ORGANIC RULES
2) Can pyrethrins containing pyperonylbutoxide (PBO) be used in organic farming? PBO is a synergist and there is no EU list of synergists that can be added ...
[96]
WHO publishes recommendations on two new types of insecticide ...
Mar 14, 2023 · WHO is issuing a strong recommendation for the deployment of pyrethroid-chlorfenapyr ITNs vs pyrethroid-only nets to prevent malaria in adults ...
[97]
Pesticide-Induced Diseases: Endocrine Disruption
Results: There was evidence that some pesticides, such as chlorpyrifos, pyrethroids, and neonicotinoids, may promote obesity and other anthropometric changes by ...
[98]
Application of the Integrated Approach to Testing and Assessment ...
Jan 28, 2025 · The present study introduces an Integrated Approach to Testing and Assessment (IATA) to evaluate the endocrine-disrupting potential of pyrethroids.Missing: review 2023-2025
[99]
Study Shows Climate Change Exacerbates Synergistic Effects of ...
Oct 25, 2024 · A study conducted in Germany highlights climate change and the heightened synergistic effects seen with pesticide exposure and food ...Missing: directions biotech
[100]
Insights into the Use of Eco-Friendly Synergists in Resistance ...
Sep 16, 2022 · It will motivate researchers to further investigate the techniques of using plant- and RNAi-based synergists in combination with insecticides.Missing: monitoring climate
[101]
Pyrethrins and Pyrethroids: A Comprehensive Review of Natural ...
Synthetic pyrethroids have replaced natural pyrethrums due to their improved effectiveness and stability against insects, making them valuable tools for pest ...Missing: alkali | Show results with:alkali
[102]
Pyrethrin Market: Global Industry Analysis and Forecast (2024-2030)
Pyrethrin Market CAGR is expected to be 5.39% during the forecast period and the market size is expected to reach nearly US$ 413.76 Mn. by 2030.