Fipronil: Considered to be at risk from chronic exposure via inhalation and dermal absorption during the application of the spray, assuming they may have to treat up to 20 large dogs per day. Fipronil is not volatile, so the likelihood of humans being exposed to this compound in the air is low.
In contrast to neonicotinoids such as acetamiprid, clothianidin, imidacloprid, and thiamethoxam, which are absorbed through the skin to some extent, fipronil is not absorbed substantially through the skin.
Ecological toxicity Edit
Fipronil is highly toxic for crustaceans, insects and zooplankton, as well as bees, termites, rabbits, the fringe-toed lizard, and certain groups of gallinaceous birds. It appears to reduce the longevity and fecundity of female braconid parasitoids. It is also highly toxic to many fish, though its toxicity varies with species. Conversely, the substance is relatively innocuous to passerines, wildfowl, and earthworms.
Its half-life in soil is four months to one year, but much less on soil surface because it is more sensitive to light (photolysis) than water (hydrolysis).
Few studies of effects on wildlife have been conducted, but studies of the nontarget impact from emergency applications of fipronil as barrier sprays for locust control in Madagascar showed adverse impacts of fipronil on termites, which appear to be very severe and long-lived. Also, adverse effects in were indicated in the short term on several other invertebrate groups, one species of lizard (Trachylepis elegans), and several species of birds (including the Madagascar bee-eater).
Nontarget effects on some insects (predatory and detritivorous beetles, some parasitic wasps and bees) were also found in field trials of fipronil for desert locust control in Mauritania, and very low doses (0.6-2.0 g a.i./ha) used against grasshoppers in Niger caused impacts on nontarget insects comparable to those found with other insecticides used in grasshopper control. The implications of this for other wildlife and ecology of the habitat remain unknown, but appear unlikely to be severe. Unfortunately, this lack of severity was not observed in bee species in South America. Fipronil is also used in Brazil and studies on the stingless bee Scaptotrigona postica have shown adverse reactions to the pesticide, including seizures, paralysis, and death with a lethal dose of .54 ng a.i./bee and a lethal concentration of .24 ng a.i./μl diet. These values are highly toxic in Scaptotrigona postica and bees in general.
In May 2003, the French Directorate-General of Food at the Ministry of Agriculture determined that a case of mass bee mortality observed in southern France was related to acute fipronil toxicity. Toxicity was linked to defective seed treatment, which generated dust. In February 2003, the ministry decided to temporarily suspend the sale of BASF crop protection products containing fipronil in France. The seed treatment involved has since been banned. Fipronil was used in a broad spraying to control locusts in Madagascar in a program that began in 1997.
Notable results from wildlife studies include:
Fipronil is highly toxic to fish and aquatic invertebrates. Its tendency to bind to sediments and its low water solubility may reduce the potential hazard to aquatic wildlife.
Fipronil is toxic to bees and should not be applied to vegetation when bees are foraging.
Based on ecological effects, fipronil is highly toxic to upland game birds on an acute oral basis and very highly toxic on a subacute dietary basis, but is practically nontoxic to waterfowl on both acute and subacute bases.
Chronic (avian reproduction) studies show no effects at the highest levels tested in mallards (NOEC) = 1000 ppm) or quail (NOEC = 10 ppm). The metabolite MB 46136 is more toxic to the parent than avian species tested (very highly toxic to upland game birds and moderately toxic to waterfowl on an acute oral basis).
Fipronil is very highly toxic to bluegill sunfish and highly toxic to rainbow trout on an acute basis.
An early-lifestage toxicity study in rainbow trout found that fipronil affects larval growth with a NOEC of 0.0066 ppm and an LOEC of 0.015 ppm. The metabolite MB 46136 is more toxic than the parent to freshwater fish (6.3 times more toxic to rainbow trout and 3.3 times more toxic to bluegill sunfish). Based on an acute daphnia study using fipronil and three supplemental studies using its metabolites, fipronil is characterized as highly toxic to aquatic invertebrates.
An invertebrate lifecycle daphnia study showed that fipronil affects length in daphnids at concentrations greater than 9.8 ppb.
A lifecycle study in mysids shows fipronil affects reproduction, survival, and growth of mysids at concentrations less than 5 ppt.
Acute studies of estuarine animals using oysters, mysids, and sheepshead minnows show that fipronil is highly acutely toxic to oysters and sheepshead minnows, and very highly toxic to mysids. Metabolites MB 46136 and MB 45950 are more toxic than the parent to freshwater invertebrates (MB 46136 is 6.6 times more toxic and MB 45950 is 1.9 times more toxic to freshwater invertebrates).
Colony collapse disorder Edit
Fipronil is one of the main chemical causes blamed for the spread of colony collapse disorder among bees. It has been found by the Minutes-Association for Technical Coordination Fund in France that even at very low nonlethal doses for bees, the pesticide still impairs their ability to locate their hive, resulting in large numbers of forager bees lost with every pollen-finding expedition. A 2013 report by the European Food Safety Authority identified fipronil as “a high acute risk to honeybees when used as a seed treatment for maize and on July 16, 2013 the EU voted to ban the use of fipronil on corn and sunflowers within the EU. The ban took effect at the end of 2013.”
Fipronil acts by binding to allosteric sites of GABAA receptors and GluCl receptors (of insects) as an antagonist (a form of noncompetitive inhibition). This prevents the opening of chloride ion channels normally encouraged by GABA, reducing the chloride ions’ ability to lower a neuron’s membrane potential. This results in an overabundance of neurons reaching action potential and likewise CNS toxicity via overstimulation.
Acute oral LD50 (rat) 97 mg/kg
Acute dermal LD50 (rat) >2000 mg/kg
In animals and humans, fipronil poisoning is characterized by vomiting, agitation, and seizures, and can usually be managed through supportive care and early treatment of seizures, generally with benzodiazepine use.