Environmental Engineering Reference
In-Depth Information
formulated to control a single pest problem, or combined to control weeds,
insects, and fungal pathogens. Indoor exposure to individual pesticides may
result from drift during application, or by passive transport on the shoes
and clothing of applicators, on the shoes of residents or their children, and
on pets. Once indoors, lawn care pesticides are protected from sunlight, rain,
elevated temperatures, and microbial action. As a consequence, they persist
on indoor dust and other surfaces for months or years as opposed to days
for the same chemicals outdoors. House dust on which pesticides accumulate
may serve as a source of exposure on resuspension. Lawn care chemicals
used exclusively outdoors, such as the herbicide 2,4-D (2,4-dichlorophenoxy
acetic acid and salts), the insecticide carbaryl (Sevin™, 1-napthylmethyl
carbamate), and the fungicide chlorothalonil (tetrachloroiso-phthalonitrile),
have all been identified in indoor environments.
a. Herbicides. The herbicide chemicals 2,4-D, dicambra (3,6-dichloro-
2-methoxybenzoic acid, 3,6-dichloro-ortho-anesic acid and salts), MCCP
(mecroprop-2,4-chloro-2-methylphenoxy propionic acid and salts), and gly-
cophosphate (Roundup TM — isopropylamine salt of n -phosphonomethyl gly-
cine) are widely used in lawn care formulations. They are applied as post-
emergent products to kill weeds selectively or for total weed (and grass)
control. Other products are used as pre-emergent chemicals to control pest
species such as crabgrass. These include Benifen, Bensulide, DCPA, Pen-
dimethalin, and Siduron.
Acid herbicides such as 2,4-D and glycophosphate are typically applied
as amine salts and have extremely low vapor pressures. They are found in
indoor air at very low concentrations and are almost always in the partic-
ulate phase.
2,4-D was detected in the air of 64 of 82 homes whose lawns had been
commercially treated. Approximately 65% of particulate phase 2,4-D mass
was associated with inhalable particles (
10
µ
g); 25 to 30% with particles
<1
m in diameter. Detectable 2,4-D residues were reported on all indoor
surfaces sampled a week after application. Track-in is the most important
route of transport indoors. For high-activity homes, 58% of 2,4-D track-in
has been estimated to be due to an indoor-outdoor dog; 25%, the applicator's
shoes; and 8%, children. Spray-drift and postapplication air intrusion appear
to be minor sources of indoor 2,4-D (
µ
1%). Once indoors, 2,4-D is subse-
quently transported to tabletops, window sills, and other horizontal surfaces
by resuspension.
4. Agricultural areas
Pesticide contamination of residences and subsequent exposure of children
and other residents may be particularly high in agricultural regions, even if
residents are not involved in farm activities. Exposure may result from
contaminated soil, dust, clothing, food, or water, or drift from spraying
operations. Residential areas in many agricultural communities are sur-
rounded by fields or orchards.
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