EPA Risk Assessment for Withdrawal of
Diazinon
On December 5, 2000, EPA released its revised risk assessment and announced an agreement with registrants to phase out/eliminate certain uses of the
organophosphate pesticide diazinon. EPA is soliciting public comments on further risk management options for this widely-used pesticide. The following links provide information on diazinon and EPA's measures to improve protection of human health and the environment.
EPA ASSESSMENT
Use/Usage:
Over 13 million lbs of diazinon are applied
annually. Use is on a variety of agricultural corps and livestock (about 20%
of usage), on turf and for residential control of various insects indoors and
outdoors (about 80% of usage). For non-ag use, the largest share is in
homeowner outdoor insect control for turf and gardens (39%). Other large usage
is in lawn care operators (19%) and pest control operators (11%). Indoor
homeowner use is also registered. California, Texas and Florida are states
with the most significant usage. Diazinon is about 1% of the Pest Control
Operator (PCO) market for indoor insecticides.
Formulations:
Diazinon is registered as dust, granules, wettable
powders, seed dressings, emulsifiable solutions, impregnated materials,
encapsulated materials, concentrates and ready-to- use solutions.
Toxicity:
Diazinon endpoints are based on plasma, red blood cell
and/or brain cholinesterase inhibition for all exposure routes and durations.
Because route specific toxicity studies are available, dermal and inhalation
absorption factors are not necessary. For inhalation, the standard uncertainty
factor of 100 was applied with an extra 3X uncertainty factor due to the lack
of a NOAEL in a rat 21-day inhalation study. Therefore, for inhalation
exposures of all durations, an MOE of 300 is acceptable. For dermal short-term
exposure, the target MOE of 100 is acceptable. For intermediate- and long-term
dermal exposure, a 3X safety factor was added to account for the extrapolation
from a 21-day dermal exposure to a longer term exposure. For intermediate- and
long-term dermal exposure, a target MOE of 300 is acceptable.
Food
Risks:
Acute and chronic dietary risk from food are acceptable
(highest sub-population is 63% for acute and 22% for chronic (children 1-6
years old).
Water
Risks:
Diazinon parent is moderately mobile and persistent.
Based on monitoring data, there is no risk concern for either groundwater or
surface derived drinking water exposure for chronic or acute. Modeling data
indicate a possible concern for infants and children age 1-6 (acute), and
children 1-6 and females age 13+ (chronic) from surface derived drinking water
only. Water estimates do not include metabolites, since toxicity and
monitoring data for these are lacking.
Residential
Risks:
The Agency has concerns for potential childrens'
exposures in the home. Potential routes of exposure for children may include
inhalation of vapors and airborne particles and dermal contact.
Occupational
Risks:
Occupational "handler" exposure to diazinon can
occur during mixing, loading and application activities. Postapplication
exposure may occur during scouting, irrigation, cultivation, harvesting and
handling seeds. The majority of occupational risk estimates for handlers
exposed to diazinon exceed the Agency's level of concern, even with personal
protective equipment (PPE) and/or engineering controls. The majority of
postapplication exposures exceed EPA's level of concern at the currently
established restricted entry interval (REI) of 24 hours.
Ecological
Risks:
Diazinon is highly toxic to birds, mammals, honey bees
and other beneficial insects. It is also very highly toxic to freshwater fish
and invertebrates following acute exposure. The endangered species levels of
concern are exceeded for terrestrial wildlife, aquatic life and terrestrial
plants.
Incidents:
Diazinon is one of the leading causes of acute
insecticide poisoning for humans and wildlife. For humans, the rate of
incidents is not high relative to its large volume of usage. The majority of
incidents occur in the home. It also is one of the top causes of bird kill
incidents.
PRESS RELEASE:
WASHINGTON, Dec. 5 — The largest producer of a widely
used pesticide said Tuesday it had reached an agreement with the Environmental
Protection Agency to phase out production of diazinon. Common in household
insect and garden sprays, diazinon is the last widely used pesticide made from
a class of chemicals — known as organophosphates — that attack the nervous
system and are believed to pose special threats to children, even at low
doses.
SYNGENTA CROP Protection USA said it would phase out its
diazinon insecticide business over four years to allow for a smooth transition
from the market. Diazinon has been marketed for more than 40 years as a home
lawn and garden insecticide. The EPA agreement bans diazinon indoors and would
eliminate outdoor use after four years. The insecticide is commonly found on
the shelves of hardware and lawn and garden shops under trade names such as
Ortho, Spectracide and Real-Kill. The chemical’s manufacturer has maintained
that the insecticide poses no health risks with normal application as
instructed on the product packages. But the manufacturers contend that the
extensive tests needed to prove the product safe under a stricter law enacted
in 1996 could not be justified, so they agreed with the phaseout, sources
said.
ATTACKS NERVOUS SYSTEM
Diazinon is one of 45 pesticides known as
organophosphates, a group of chemicals derived from the same family as the
sarin nerve gas agent developed during World War II.
Under the Food Quality Protection Act, passed by Congress
in 1996, the EPA is required to restrict or ban a pesticide’s use if it
poses a specific threat to children. Last May, an EPA draft study concluded
that diazinon might pose a greater health risk than previously thought. It is
one of several widely used pesticides that the EPA has restricted or banned as
part of its review of organophosphates. In June, the agency, also citing
health risks to children, banned the chemical chlorpyrifos for use in gardens
and homes. Chlorpyrifos for decades was widely used under the trade name
Dursban in everything from flea collars to bug spray for gardens and lawns.
Some restricted agricultural uses for chlorpyrifos were continued.