. 10th ed. Surrey, UK: The British Crop Protection Council, 1994., p. 4] **PEER REVIEWED**


Metabolism/Pharmacokinetics:


Mechanism of Action:
Insecticide and acaricide with contact and stomach action. ... Acts by stimulating the release of gamma-aminobutyric acid, an inhibitory neurotransmitter, thus causing paralysis.
[Tomlin, C.D.S. (ed.). The Pesticide Manual - World Compendium. 10th ed. Surrey, UK: The British Crop Protection Council, 1994., p. 4] **PEER REVIEWED**


Pharmacology:


Environmental Fate & Exposure:


Environmental Fate/Exposure Summary:
Abamectin's production and use as an insecticide and acaricide is expected to result in its direct release to the environment. Abamectin is also known as avermectin B1 which is found in two forms, B1a and B1b; it is a mixture containing at least 80% of avermectin B1a and not more than 20% of avermectin B1b. Abamectin is found in nature as one of the compounds produced by the soil microbe Streptomycetes avermitilis. If released to air, an estimated vapor pressure of 1.5X10-9 mm Hg indicates abamectin will exist solely in the particulate phase in the ambient atmosphere. Particulate-phase abamectin will be removed from the atmosphere by wet and dry deposition. There is the potential for the photodegradation of abamectin in air; however, the rate at which this process may occur is not known. If released to soil, abamectin is expected to have no mobility based upon a Koc of 5000. Volatilization from moist soil surfaces is not expected to be an important fate process based upon an estimated Henry's Law constant of 1.7X10-7 atm-cu m/mole. Abamectin is not expected to volatilize from dry soil surfaces based upon its vapor pressure. Biodegradation in soil may be an important environmental fate process as soil half-lives of 2 weeks to 2 months have been reported. If released into water, abamectin is expected to adsorb to suspended solids and sediment based upon the Koc. Volatilization from water surfaces is not expected to be an important fate process based upon this compound's estimated Henry's Law constant. A BCF of 56 suggests bioconcentration in aquatic organisms is moderate. Abamectin is stable to hydrolysis at pH levels of 5, 7 and 9. Occupational exposure to abamectin may occur through dermal contact with this compound at workplaces where abamectin is produced or used. (SRC)
**PEER REVIEWED**


Probable Routes of Human Exposure:
Occupational exposure to abamectin may occur through dermal contact with this compound at workplaces where abamectin is produced or used(SRC). A study of worker re-entry exposure in greenhouses showed that abamectin present on chrysanthemum seedlings as dislodgeable foliar residues, following both low- and high-volume spraying at 0.09 g ai/1000 sq m, had half-lives of 1.1 and 2.4 days, respectively(1). A study of worker exposure to abamectin on 12 rose culture farms in greenhouses found that dermal exposure was 13 ug/hr approximately 23 hours after treatment; similar